I have a 250 kawasaki kle which is basically a zzr250 in semi trail form. That screw meters air. Usually, I would expect the clip to be one position lower than stock and the mains 1-2 sizes bigger than stock. Thanks again for you response I really appreciate it! Only the needle jet (atomizer with its bush) were changed, the idle jet is the same again. Thanks for the compliments! Or find a #4 washer .040 thick and shim needles up. My mixture is at 2 3/4 and if i go leaner it seems like the idle drops and isnt as smooth. Most likely an air screw. Eventually Ill be upgrading to a k&n air filter eventually so I just want to get an idea of what my carb should be set at. I have a short video of my ATV condition. Yes pilot jet is the slow jet, same thing. The timing advance is just the factory key for Austria. Sounds like youll have to take carb apart and record all jet #s and compare to stock and go from there. Why are you trying to lean it out so much? 3 weeks ago I finally have enough time for the carb cleaning and applying the new stuff in it. Thats what I have been experiencing with this bike. Im not too familiar with the carb you have, however did a bit of reading and that screw meters fuel, not air like I stated before. Still better then with the 15s but not fixed yet.
My airbox does have holes drilled into the back of it though. Thanks. How many turns out? Ive seen the pilot air screw on the engine side on most Amal carburetors. Engine begins to sputter as you increase throttle position to full throttle. and change all the vacum pipes Get a 165 and 168. I usually never change float height to mask a jetting issue. Farming, Beef, Dairy, Insect, Equipment, ETC. It seems that the bike is running lean from the spark plug readings. How-To: Size Your Pilot Jet, Pilot Screw Explained, https://howtomotorcyclerepair.com/vulcancarbclean/, https://www.youtube.com/watch?v=5AqqQ6jnR5I, https://howtomotorcyclerepair.com/how-to-tune-a-motorcycle-main-jet/, https://howtomotorcyclerepair.com/contact/, https://www.denniskirk.com/ebc/rd-vm22-210-pilot-jets.p173396.prd/17339610.sku, https://mega.nz/file/6c0Qza5S#1UcD9fP3szSm78XdOmEw1XITLjR8Wk8nNcdiT2J3VP4, https://www.amazon.com/dp/B07CY9D2W8?psc=1&ref=ppx_yo2_dt_b_product_details, 8 MUST Have Modifications Harbor Freight Blast Cabinet, How-To: Prevent flash rust on metal parts, How-To: WOOD DIY Vapor Blast/Dry Blast Plans 4230 & 6040, How-To: MRCOOL DIY Mini Split Installation. Im 100% sure its not a bog lets just put it that way lol. How does each sound? Any suggestions? Since your best idle is at almost closed fuel screw position, I would decrease pilot by 1-2 sizes and see if you can get fuel screw in the 1-3 turns out range. Dont worry about the main jet or pilot air jet right now. When i start the bike, runs in ideal RPM in idle (no ups and downs, no sudden fluctuations, no idle hunting) just stable RPMs. A pilot fuel screw will also be made of brass, gold in color, and will have a pointy needle tip. Thanks.
I can cruise in 6th and go wide open and she gets right up and goes. What is the stock main? Runs terrible at those settings. Its 82 model. Wondering if maybe i had a float stuck and not all the way seated and filled the cylinder full of fuel or something. All carbs should have the same fuel screw setting, for example, all should be 3 turns out. How many turns out for smoothest and highest peak RPM with the 17.5? and what size up or down will be a leaner pilot? And no its not adjustable. Sometimes bikes are very lean from the factory. yes indeed. How does tuning two carbs differ from one carb if it differs at all? Does it bog ? If not, you have to take care of them. Im running standard jet but after reading some other comments it looks like i need to up the pilot jet a size or two. Also, is the timing advance adjustable? Or air cleaner / exhaust modifications? As far as drilling the slide i know i havent done it but thats not saying someone else didnt. It was 3 1/2 though so im thinking i will be putting in 20s next because it rode smooth and nice for about 10 minutes then it went back to its figgity self and was hesitating again. But finally I was able to go another 1/4 turn in and take it for a ride. The jets came in tomorrow, but as it turned out, the 36 is still too big. But im starting to think i either have a battery issue or a starter issue. and fuel screw 2.75 out. It's ALWAYS good insurance to have an auxillary inline fuel filter that you can positively see, and positively know, it's filtering the fuel before troubles arise. Yes it is the Matt your thinking of. Thanks! What is the white smoke all about? The bike has aftermarket air pods and Vance and Hines exhaust. You sure your carb boots are tightened down, no exhaust leaks anything like that!? Smaller carburetors may require a modification to the throttle stop to open all the way. It did run good for about a month but then I started to lose throttle response so I synced and that problem went away.
When you close the throttle and decelerate, the engine runs lean, and can pop through the exhaust. But it was more of a lack of throttle response. Ive got mods and the carb was professionally jetted. Have you verified the pilot jet size in service manual? : removing and dismantling the engine for internal inspection (rings, valves, timing chain setting, valve tappet clearance setting, etc.) Your email address will not be published. Now that you have them synched and you best idle is 4+ turns out, you need to go larger on pilots. And will pulling the baffles help to correct the problem by leaning the mixture out a bit and allowing me to turn a/f screws in without having popping. Would it ruin the clutch? I know that the stock air cleaner is very restrictive. Thanks for the help!! Also what bugs me is that I cant adjust the idle screws because it wont idle, but if I adjust them with the minimum amount of gas needed to not die, the revs are the highest when the mixture screw is all the way in (it meters fuel). I do believe the 45 slow jet is not enough to get the bike started reliably. Anywhere 1 1/2 turns or more the idle stays the same till about 2 1/2 no change at all. I know this should be a little hard to say, but how much of a change does one usually go with the cutaways, considering I have the 45 and the others being 40, 50 and 55? Hi, Mathew its Brent again dont know if you remember me but my gsxr is running weird again.
This is achieved by turning the idle screw CCW. Because when doing the carb synch i noticed the slides would flutter alot when revving. If your idle is set too high (throttle blades open too much), then any adjustments made by fuel screw may not be noticed. It was probably 75% gas. My problem is cold starting. :thumbsup: Great posting about how carburators work and to also add a very important piece of advice. It ran good. I pulled off the vacuum line to the fuel valve and it was wet and had alittle bit of fuel in it. Ill be sure to do that this weekend, what do you mean by Read the plugs? Another thing, you checked the vacuum petcock? Archive - The fuel screw is covered by a plug on the YFZ's. So if it needs to be leaner or richer at 1/8 you have to swap the actual jets. 2012 klr650 w/CV40 carb,just made changes from stock: I lightly seated the pilot needles, backed out to 2-1/2 turns, started and warmed the engine and the best idle was at 3-1/2 turns. Im trying to tune my 73 Cl350. Thanks for the info. If you add more throttle during stumble does it go away? Ive got a Suzuki GSX1200 Inazuma which I modified a bit as a cafe racer. So Im confident were heading in the right direction. Ive tried shifting the fuel screw from full in to 3.5 turns out, in quarter turn increments from full in, but I still cant get the thing to idle without choke. If it's like most motorcycles(which an ATV engine really is), the factory probably only relied on the "sock filter" that's attached permanently onto the fuel petcock that goes up into the fuel tank, and it's something you don't see or think about until you have carburator and fuel issues. Raptorforme93, So i run race gas almost always. I have a 2004 ltz400 and the quad runs best with fuel screw closed the pilot jet is the stock 22.5 and everywhere I read says this is correct. Usually, it's about 1.5 turns. Per the advice of my local Honda Dealer, I installed 122 & 188 main jets. Thats all my modification (no exhaust modifications). 185 (pilot air). Reading spark plugs gives you indication of whether it is running rich, lean, or just right. if i turn out more 2,5 the engine start stumble and turn in all the screw, the engine dies. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Copyright 2022 How-To Motorcycle Repair. Now that your fuel screws are nearing 1.25 out, you can get a leaner cruise (1/16-1/8) throttle by dropping pilot jet size. Hello Matthew, After fitting on new engine I cannot get Carb 4 to operate correctly, engine idles but only on top three cylinders. I ended up going to the 2.5. Compatibility information is not available for this item. Enter your name and email to get notified when new content becomes available. Also now Im certain that the fuel level indeed is high enough to pour into these side holes as the needle jet was soaking wet to the top when I took it out, aside from the fact that it runs pretty well with the holes closed. But when run test, the engine feel rich and the spark plug is black. So I took it for a long ride. Pb rev limiter is an issue on most of Yamaha bikes. I am building a 97 XR70 engine with an 88cc kit, race head, 0.275 lift cam, and high-flow exhaust. Bike runs amazing if Im flogging it. Most kits supply a 1/8 drill bit for this, so stock should be smaller. The pilot is adjusted for max RPM and hopefully is in the 1-3 turns out range. Hi Matthew, I have been watching your videos and admiring your work on carburetors. This is the engine telling you it is happy, and it runs best at this mixture.
Also, is the ignition system in good shape?
They are usually stamped on the bottom. It starts first kick on half choke. If not, maybe jump 4 sizes on main. Maybe. You'll need to take off the intake assembly all the way to the carb, then loosen the rubber coupling (between the carb and cylinder head). I have tried a plug chop before to no avail. And let you know what i find. Already synced them up good and all the other usual non carburetor items have been checked. If you can close them and engine still runs, the pilot jets are too big. So i held the throttle wide open and it turned and fired atleast. Is that an accurate way to see if a leak in the boot is whats causing my problem? Supposedly he worked for Universal Studios fixing all kinds of machines anyway thank you for help. So with the jet needle change only it will not idle? The store will not work correctly in the case when cookies are disabled. Could that be the cause of everything i have been experiancing? 2. The ATV's carburators work by "gravity feed" and ARE NOT under any pressure at all.
If it bleeds off, replace it. I would try readjusting your fuel screw. *Update* Yea I just realized that its called a fuelscrew. I did find something that may be throwing a wrench in the gears tho. And the guy that had it before me didnt cut corners with this bike. You either have a rich mixture, or a lean mixture. I will be using a Keihin PE26mm carb that I had from a previous build. Content on raptorforum.com is generated by its users. Also dont go crazy in torque since the screw is brass. And jetting now? I have already ordered 3 of them, the one that is currently in is a size 45 (the biggest sold for this carb), and Ive ordered a size 40, 38 and 36. new uni filter. If it ran good at a certain setting and all of a sudden started running bad, it is not the settings. Is the bike stock?
If you dont feel like doing it Id understand, I imagine you are getting pretty burned out on people always asking for help, I know I would be. Has anything been done to CV slide and/or spring? Since you shortened the silencer, decel pop may be normal. Black covered in soot. It has 8 side holes on the top end, whereas the 2 stroke version doesnt have any (it was a size 266). But the only thing i have changed is the mixture. Awesome! Found this place, the screw was cheaper, and the shipping was fast & free. and the spark plug was black. So yeah, she runs worse now, and I really dont know what else I can do. Currently Active Users Viewing This Thread: 1, The following errors occurred with your submission, ATVConnection.com ATV Enthusiast Community. Ok now this one has got me scratching my head. If so, how many turns out for max idle RPM and smoothness. I have an 82 Susuki GS650G, Canadian Model. Probably overkill for this engine. Hondas are red, Yamies are blue, and damn right I'm faster than YOU!! They should both be turned out the same amount. After I talked to you it ran good for about a month and then it started to run bad again. If not, I dont know what else I can do. Do we adjust that too?? once it starts it idles for maybe 2-5 seconds and it dies, weve tried I even fitted a brand new carb but got the same issue. Too much advance can cause bucking like you described.
Electric tape, RTV, etc..never seem to hold up. You mentioned vacuum leaks. Makes perfect sense. There probably is some way to adjust the fuel mixture via a pilot air or fuel screw. To answer the different main jet in twins question, one side of twin will run hotter than the other, specially in air/fan cooled machines.
Hey Brent, try shutting the fuel off and running the carbs dry before letting the bike sit overnight. https://www.amazon.com/dp/B07CY9D2W8?psc=1&ref=ppx_yo2_dt_b_product_details. the popping is finally gone (about 3 turns out on pilot screw). I am getting alot of popping on startup / idle along with decel. 1. A carb will have an air screw or a fuel screw 99% of the time. Buy a cheap flathead screwdriver and grind the tip so it fits the slot perfectly. Thanks for any help with this.. Due to time problems I have yet to do either. If you can do that by twisting the carb and do it through the port in the bottom of the float bowl, then you'll be fine. Since your bike has some engine work, I'd really hope that it already had a thumbwheel for the A/F installed. Hi, I own a 1986 Yamaha fazer. Now the engine wouldnt die when I fully close the screw. Give it 2 drain and fills and it will be OK. Also I hear a strange tick in a hose on the right side that has a metal spring over it. If you dont have a float level spec, I like to set the level about 2mm below the carb body and float bowl mating line. Before taking it apart, spray carb clean at boots and see if there are any vacuum leaks. But I havent turn them all the way in or all the way out. Pull the spark plug and take a look at what color it is. If I pull choke out more it dies. I changed mains to 120 and it solved my problem. Adjusted floats the max both ways.Oh 115 main jet. Remove air cleaner and tape all but the bottom 1/8-1/4 of carb inlet and see if conditions improve. just for a basic start point when i adjust mine. You mentioned plugs are black (rich) and it bogs (lean?). I had to replace the pilot jet. I do quite a bit of work on a 87. My concern: would this impact high RPM performance? Drop them back down to stock. Find a different shop! How do they affect rpms as they are occurring? Need a little help with cable adjustment on a2005 Yamaha grizzley 80. That part does not make sense to me. It says its supposed to read between 3.5-6.5 k ohms and mine was reading 16.28 ish. Its a bit of guess work as I have no rev counter, but it idles nicely mid to high revs seem good but its a bit boggy about a quarter up the rev range I would say! Also my temp is around 70s right now and altitude is 1400s above sea level, Sounds good. It also does this while riding. Please try again later. Thanks! Oh and I have the next size up and its 17.5 should I go 2 steps and get the 20? Maybe the stumble you are trying to solve is the transition between pilot circuit and throttle valve. All should seal if float is depressed. Thanks for helping me man. So I put in the next size smaller pilot jets and it took a massive leap to the better side. Turn each out 1/4 turn at a time until it stumbles. I did try closing the fuel mixture screw all the way in, but the bike does not die. It's called a "stone" fuel filter in that you'll see what looks like a golden stone inside the filter housing.
If my idle was set to high would that maybe cause the blades to be open all the time and possibly cause this? How would this work on a bike with two carbs? I will update again when i get the new one on and test ride it. Brent, if it is stumbling/bogging/hesitating, you will need to go richer. If it is a lean bog, more throttle will not help it recover. How to i adust the jet screw ,whether i want to turn clockwise or anti clockwise.
The first step is to determine if you have an AIR screw that meters air, or a FUEL screw that meters fuel. Try to to lean the screw its not helping. Got mine from eBay $10 shipped idk the brand but just like tusk. Just as i had thought the mixture chnage made no difference.
Should I just disregard the manual? So I never worked on bikes carb, cleaned carbs. Sweet, Thanks man.
I know its between here and 2 1/4 because at 2 1/4 with choke it hydrolocks when i try to start it and thats obveously not right lol. What is your setup here? Do Not Sell My Personal Information -, By logging into your account, you agree to our. Adjust the fuel screws and note how many turns out. Try the size up you have and see what happens. You really know your stuff! So i installed it per the manual. to find these in excellent condition and per factory specs; spark plug in acceptable condition; replaced fuel line; completely rebuilding carburetor with new primer, changing main needle jet to slot 2 and slot 4 of a 5-slop jet adjustment to see if performance changes; and verifying that air cleaner and exhaust system are not restricted. I dont know if drilling the hole is a good idea or not. Sure, what specifically? October 28, 2009 in Sport ATV. they also have drive belts that last forever. It may be hidden under a welch plug or cap. Air fuel mixture screw is out 1.5 turns.
Its impossible to adjust stocker. It runs better without the air filter, and also if I turn the screw out the exhaust starts to smoke heavily. I have read a few carb books over the years and it was always confusing. With the 17.5, is the screw responsive? The engine side passage is further trimmed or metered by the fuel screw. I have dismantled and inspected the carburetor three times to check for other potential carburetor problems with jets and passages. The Fora platform includes forum software by XenForo, VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada, grizzlycentral.com is an independent Yamaha enthusiast website owned and operated by VerticalScope Inc. Thanks. Thanks for advice. Get back to me on what you have. They work opposite of each other so it is important to know that before performing this procedure. Thanks! Now heres a question. I found that my pilot screw needle hole is bigger. I recently purchased a 2000 Honda Sabre VT1100C2 with 16000 miles. Idle is fine however when i drive it if i ease the throttle it boggs if i open the throttle on full it just perfect what do you suggest stock pilot screw is 40. The screw with white thumb adjuster knob on engine side, is the fuel screw, and stock setting is 2.5 out. https://www.youtube.com/watch?v=FDRg49vzdxk. and if I screw all in, the engine will dies. What year make model? Hope you can help. Here is some reading: http://www.dotheton.com/forum/index.php?topic=29838.15.
So could my idle be set to high and cause samething? And out if I go any further than 2 3/4 it idles rough and 3 or further it is about to stall. I have a 2005 polaris predator 500. I too have some small filters on, but have a aftermarket exhaust with more flow through. And its not that my bike backfires at all, it actually doesnt ever backfire, its that when I give it a good long rev itll settle down quickly but when I give it a short rev the rpms "hang" before it settles down to idle. Its odd that you get 2 turns out with 17.5, and 5 turns out with 15. So Ive changed the pilot jet leaner to 15. Ive got an 85 GS700 that I have personally rebuilt the engine on 2 1/2 times. Since my last post it has been to cold to ride until today so i went out and went a half turn more fuel.
would a overly-rich pilot FUEL screw offer the following symptoms: I was always under the assumption that carbs our of sync would lack throttle response and I always though it was very responsive. After idle, number 4 plug is petrol wet when pulled. Yes i did do a pressure test and all was good after that one little hiccup. Secnodly, I have a problem.
But wheni i pull throttle a little bit in idle to cca 2-4K RPMs, and release throttle, the RPMs are going slow to normal. Also, can you send me a link to the jet kit? Any ideas or suggestions would be greatly appreciated. What do you think?
Rev engine in neutral and note how RPMs return to idle. But I have a carb problem that no one cause solve!I have a 1985 CB700SC with low miles. Carb synch is most important at idle and least important at WOT. Is the carb clean? If I cant fix it myself, I dont want to keep it.
Advertising - I have acquired this ATV not knowing the operating condition other than it has been unused for several months. To verify, remove the screw and it it has a blunt tip then it meters air. I have some questions for you: 1) looking at this link ( CARBURATOR OEM KAWASAKI ZRX1200R), https://www.kawasakioriginalparts.com/road-bikes.html?blockref=99912-1179.C-10&machineid=660&year=2005&model=ZR1200-A5H&country=XX. Just an update. I purchase an 81 Suzuki gs450, I can get the motor to idle without full choke on the previous owner took off the stock exhaust and added an aftermarket system with out baffles. Dellorto PHF carb, 52 pilot, air screw 2,5 turns out for ideal throttle response. So Im hoping to just adjust the mixture to fix it. Vintage Machines.. Pre 1975, Dirt bikes, ATV's, MiniBikes, Snowmobiles, etc. Side x Sides / Sport and Utility Discussion. Thanks buddie. Runs good. Should I buy larger pilot jets? Do you feel like trading a beer for a diagnosis? Ran amazing. Im wondering if that diaphragm has a hole in it. Do you always run VP110?
JavaScript is disabled. I cant seem to adjust it. I like to take 3-5psi of air and blow into fuel inlet. One correction to your otherwise excellent site, the Mikuni VM series carbs have both a pilot fuel screw and pilot air screw for tuning the idle circuit. I tryed to set the mixtures and it was all over the place 1/4 turn idle up. 2003 Polaris xc700 2 stroke. You should follow the rest of my suggestions and you will see that it will run great (1 & 3). Temp is 70 degrees here and the temp at 60 down the highway was about 170-180s and in town it would creep up to 200+ one thing I did notice is that I was able to slowly ease off the throttle without it bucking and kicking and it was much smoother at cruising speed in 6th gear at 60 giving like a 1/16th throttle. Trying a 1/4 turn more fuel tomorrow.
I put in the next size bigger pilot jet (17.5) and it made it run quite a bit smoother. And need help. Thanks again. I had a 62 and 70 slow jet. Put it all back together and fired it up. Bikes are lean from the factory period. also (engine side) Fuel mixture screw does not seem to make any difference at all even fully seated or out 7 turns. The fuel screw setting at idle trims the pilot fuel, and considering the fuel screw ends up at 1.5/1.75, the 1/8 throttle position (all 100% pilot flow) will be rich. So here are my findings. The hesitation, is it a bog (lean) or rich (sputter)? His pilot needle only sticks out about 0.5 mm when close all the way in, but mine is about 2mm out of the hole. What does the plug look like after idling for a few minutes? Let me know what happens when you get the tps working properly. Hey Saber6, i was just adjusting my fuel screw and air screw last weekend because my bike does not idle and when starting it, it spits and spudders. These require special fuel filters and special designed fuel lines.
My airbox does have holes drilled into the back of it though. Thanks. How many turns out? Ive seen the pilot air screw on the engine side on most Amal carburetors. Engine begins to sputter as you increase throttle position to full throttle. and change all the vacum pipes Get a 165 and 168. I usually never change float height to mask a jetting issue. Farming, Beef, Dairy, Insect, Equipment, ETC. It seems that the bike is running lean from the spark plug readings. How-To: Size Your Pilot Jet, Pilot Screw Explained, https://howtomotorcyclerepair.com/vulcancarbclean/, https://www.youtube.com/watch?v=5AqqQ6jnR5I, https://howtomotorcyclerepair.com/how-to-tune-a-motorcycle-main-jet/, https://howtomotorcyclerepair.com/contact/, https://www.denniskirk.com/ebc/rd-vm22-210-pilot-jets.p173396.prd/17339610.sku, https://mega.nz/file/6c0Qza5S#1UcD9fP3szSm78XdOmEw1XITLjR8Wk8nNcdiT2J3VP4, https://www.amazon.com/dp/B07CY9D2W8?psc=1&ref=ppx_yo2_dt_b_product_details, 8 MUST Have Modifications Harbor Freight Blast Cabinet, How-To: Prevent flash rust on metal parts, How-To: WOOD DIY Vapor Blast/Dry Blast Plans 4230 & 6040, How-To: MRCOOL DIY Mini Split Installation. Im 100% sure its not a bog lets just put it that way lol. How does each sound? Any suggestions? Since your best idle is at almost closed fuel screw position, I would decrease pilot by 1-2 sizes and see if you can get fuel screw in the 1-3 turns out range. Dont worry about the main jet or pilot air jet right now. When i start the bike, runs in ideal RPM in idle (no ups and downs, no sudden fluctuations, no idle hunting) just stable RPMs. A pilot fuel screw will also be made of brass, gold in color, and will have a pointy needle tip. Thanks.
I can cruise in 6th and go wide open and she gets right up and goes. What is the stock main? Runs terrible at those settings. Its 82 model. Wondering if maybe i had a float stuck and not all the way seated and filled the cylinder full of fuel or something. All carbs should have the same fuel screw setting, for example, all should be 3 turns out. How many turns out for smoothest and highest peak RPM with the 17.5? and what size up or down will be a leaner pilot? And no its not adjustable. Sometimes bikes are very lean from the factory. yes indeed. How does tuning two carbs differ from one carb if it differs at all? Does it bog ? If not, you have to take care of them. Im running standard jet but after reading some other comments it looks like i need to up the pilot jet a size or two. Also, is the timing advance adjustable? Or air cleaner / exhaust modifications? As far as drilling the slide i know i havent done it but thats not saying someone else didnt. It was 3 1/2 though so im thinking i will be putting in 20s next because it rode smooth and nice for about 10 minutes then it went back to its figgity self and was hesitating again. But finally I was able to go another 1/4 turn in and take it for a ride. The jets came in tomorrow, but as it turned out, the 36 is still too big. But im starting to think i either have a battery issue or a starter issue. and fuel screw 2.75 out. It's ALWAYS good insurance to have an auxillary inline fuel filter that you can positively see, and positively know, it's filtering the fuel before troubles arise. Yes it is the Matt your thinking of. Thanks! What is the white smoke all about? The bike has aftermarket air pods and Vance and Hines exhaust. You sure your carb boots are tightened down, no exhaust leaks anything like that!? Smaller carburetors may require a modification to the throttle stop to open all the way. It did run good for about a month but then I started to lose throttle response so I synced and that problem went away.
When you close the throttle and decelerate, the engine runs lean, and can pop through the exhaust. But it was more of a lack of throttle response. Ive got mods and the carb was professionally jetted. Have you verified the pilot jet size in service manual? : removing and dismantling the engine for internal inspection (rings, valves, timing chain setting, valve tappet clearance setting, etc.) Your email address will not be published. Now that you have them synched and you best idle is 4+ turns out, you need to go larger on pilots. And will pulling the baffles help to correct the problem by leaning the mixture out a bit and allowing me to turn a/f screws in without having popping. Would it ruin the clutch? I know that the stock air cleaner is very restrictive. Thanks for the help!! Also what bugs me is that I cant adjust the idle screws because it wont idle, but if I adjust them with the minimum amount of gas needed to not die, the revs are the highest when the mixture screw is all the way in (it meters fuel). I do believe the 45 slow jet is not enough to get the bike started reliably. Anywhere 1 1/2 turns or more the idle stays the same till about 2 1/2 no change at all. I know this should be a little hard to say, but how much of a change does one usually go with the cutaways, considering I have the 45 and the others being 40, 50 and 55? Hi, Mathew its Brent again dont know if you remember me but my gsxr is running weird again.
This is achieved by turning the idle screw CCW. Because when doing the carb synch i noticed the slides would flutter alot when revving. If your idle is set too high (throttle blades open too much), then any adjustments made by fuel screw may not be noticed. It was probably 75% gas. My problem is cold starting. :thumbsup: Great posting about how carburators work and to also add a very important piece of advice. It ran good. I pulled off the vacuum line to the fuel valve and it was wet and had alittle bit of fuel in it. Ill be sure to do that this weekend, what do you mean by Read the plugs? Another thing, you checked the vacuum petcock? Archive - The fuel screw is covered by a plug on the YFZ's. So if it needs to be leaner or richer at 1/8 you have to swap the actual jets. 2012 klr650 w/CV40 carb,just made changes from stock: I lightly seated the pilot needles, backed out to 2-1/2 turns, started and warmed the engine and the best idle was at 3-1/2 turns. Im trying to tune my 73 Cl350. Thanks for the info. If you add more throttle during stumble does it go away? Ive got a Suzuki GSX1200 Inazuma which I modified a bit as a cafe racer. So Im confident were heading in the right direction. Ive tried shifting the fuel screw from full in to 3.5 turns out, in quarter turn increments from full in, but I still cant get the thing to idle without choke. If it's like most motorcycles(which an ATV engine really is), the factory probably only relied on the "sock filter" that's attached permanently onto the fuel petcock that goes up into the fuel tank, and it's something you don't see or think about until you have carburator and fuel issues. Raptorforme93, So i run race gas almost always. I have a 2004 ltz400 and the quad runs best with fuel screw closed the pilot jet is the stock 22.5 and everywhere I read says this is correct. Usually, it's about 1.5 turns. Per the advice of my local Honda Dealer, I installed 122 & 188 main jets. Thats all my modification (no exhaust modifications). 185 (pilot air). Reading spark plugs gives you indication of whether it is running rich, lean, or just right. if i turn out more 2,5 the engine start stumble and turn in all the screw, the engine dies. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Copyright 2022 How-To Motorcycle Repair. Now that your fuel screws are nearing 1.25 out, you can get a leaner cruise (1/16-1/8) throttle by dropping pilot jet size. Hello Matthew, After fitting on new engine I cannot get Carb 4 to operate correctly, engine idles but only on top three cylinders. I ended up going to the 2.5. Compatibility information is not available for this item. Enter your name and email to get notified when new content becomes available. Also now Im certain that the fuel level indeed is high enough to pour into these side holes as the needle jet was soaking wet to the top when I took it out, aside from the fact that it runs pretty well with the holes closed. But when run test, the engine feel rich and the spark plug is black. So I took it for a long ride. Pb rev limiter is an issue on most of Yamaha bikes. I am building a 97 XR70 engine with an 88cc kit, race head, 0.275 lift cam, and high-flow exhaust. Bike runs amazing if Im flogging it. Most kits supply a 1/8 drill bit for this, so stock should be smaller. The pilot is adjusted for max RPM and hopefully is in the 1-3 turns out range. Hi Matthew, I have been watching your videos and admiring your work on carburetors. This is the engine telling you it is happy, and it runs best at this mixture.
Also, is the ignition system in good shape?
They are usually stamped on the bottom. It starts first kick on half choke. If not, maybe jump 4 sizes on main. Maybe. You'll need to take off the intake assembly all the way to the carb, then loosen the rubber coupling (between the carb and cylinder head). I have tried a plug chop before to no avail. And let you know what i find. Already synced them up good and all the other usual non carburetor items have been checked. If you can close them and engine still runs, the pilot jets are too big. So i held the throttle wide open and it turned and fired atleast. Is that an accurate way to see if a leak in the boot is whats causing my problem? Supposedly he worked for Universal Studios fixing all kinds of machines anyway thank you for help. So with the jet needle change only it will not idle? The store will not work correctly in the case when cookies are disabled. Could that be the cause of everything i have been experiancing? 2. The ATV's carburators work by "gravity feed" and ARE NOT under any pressure at all.
If it bleeds off, replace it. I would try readjusting your fuel screw. *Update* Yea I just realized that its called a fuelscrew. I did find something that may be throwing a wrench in the gears tho. And the guy that had it before me didnt cut corners with this bike. You either have a rich mixture, or a lean mixture. I will be using a Keihin PE26mm carb that I had from a previous build. Content on raptorforum.com is generated by its users. Also dont go crazy in torque since the screw is brass. And jetting now? I have already ordered 3 of them, the one that is currently in is a size 45 (the biggest sold for this carb), and Ive ordered a size 40, 38 and 36. new uni filter. If it ran good at a certain setting and all of a sudden started running bad, it is not the settings. Is the bike stock?
If you dont feel like doing it Id understand, I imagine you are getting pretty burned out on people always asking for help, I know I would be. Has anything been done to CV slide and/or spring? Since you shortened the silencer, decel pop may be normal. Black covered in soot. It has 8 side holes on the top end, whereas the 2 stroke version doesnt have any (it was a size 266). But the only thing i have changed is the mixture. Awesome! Found this place, the screw was cheaper, and the shipping was fast & free. and the spark plug was black. So yeah, she runs worse now, and I really dont know what else I can do. Currently Active Users Viewing This Thread: 1, The following errors occurred with your submission, ATVConnection.com ATV Enthusiast Community. Ok now this one has got me scratching my head. If so, how many turns out for max idle RPM and smoothness. I have an 82 Susuki GS650G, Canadian Model. Probably overkill for this engine. Hondas are red, Yamies are blue, and damn right I'm faster than YOU!! They should both be turned out the same amount. After I talked to you it ran good for about a month and then it started to run bad again. If not, I dont know what else I can do. Do we adjust that too?? once it starts it idles for maybe 2-5 seconds and it dies, weve tried I even fitted a brand new carb but got the same issue. Too much advance can cause bucking like you described.
Electric tape, RTV, etc..never seem to hold up. You mentioned vacuum leaks. Makes perfect sense. There probably is some way to adjust the fuel mixture via a pilot air or fuel screw. To answer the different main jet in twins question, one side of twin will run hotter than the other, specially in air/fan cooled machines.
Hey Brent, try shutting the fuel off and running the carbs dry before letting the bike sit overnight. https://www.amazon.com/dp/B07CY9D2W8?psc=1&ref=ppx_yo2_dt_b_product_details. the popping is finally gone (about 3 turns out on pilot screw). I am getting alot of popping on startup / idle along with decel. 1. A carb will have an air screw or a fuel screw 99% of the time. Buy a cheap flathead screwdriver and grind the tip so it fits the slot perfectly. Thanks for any help with this.. Due to time problems I have yet to do either. If you can do that by twisting the carb and do it through the port in the bottom of the float bowl, then you'll be fine. Since your bike has some engine work, I'd really hope that it already had a thumbwheel for the A/F installed. Hi, I own a 1986 Yamaha fazer. Now the engine wouldnt die when I fully close the screw. Give it 2 drain and fills and it will be OK. Also I hear a strange tick in a hose on the right side that has a metal spring over it. If you dont have a float level spec, I like to set the level about 2mm below the carb body and float bowl mating line. Before taking it apart, spray carb clean at boots and see if there are any vacuum leaks. But I havent turn them all the way in or all the way out. Pull the spark plug and take a look at what color it is. If I pull choke out more it dies. I changed mains to 120 and it solved my problem. Adjusted floats the max both ways.Oh 115 main jet. Remove air cleaner and tape all but the bottom 1/8-1/4 of carb inlet and see if conditions improve. just for a basic start point when i adjust mine. You mentioned plugs are black (rich) and it bogs (lean?). I had to replace the pilot jet. I do quite a bit of work on a 87. My concern: would this impact high RPM performance? Drop them back down to stock. Find a different shop! How do they affect rpms as they are occurring? Need a little help with cable adjustment on a2005 Yamaha grizzley 80. That part does not make sense to me. It says its supposed to read between 3.5-6.5 k ohms and mine was reading 16.28 ish. Its a bit of guess work as I have no rev counter, but it idles nicely mid to high revs seem good but its a bit boggy about a quarter up the rev range I would say! Also my temp is around 70s right now and altitude is 1400s above sea level, Sounds good. It also does this while riding. Please try again later. Thanks! Oh and I have the next size up and its 17.5 should I go 2 steps and get the 20? Maybe the stumble you are trying to solve is the transition between pilot circuit and throttle valve. All should seal if float is depressed. Thanks for helping me man. So I put in the next size smaller pilot jets and it took a massive leap to the better side. Turn each out 1/4 turn at a time until it stumbles. I did try closing the fuel mixture screw all the way in, but the bike does not die. It's called a "stone" fuel filter in that you'll see what looks like a golden stone inside the filter housing.
If my idle was set to high would that maybe cause the blades to be open all the time and possibly cause this? How would this work on a bike with two carbs? I will update again when i get the new one on and test ride it. Brent, if it is stumbling/bogging/hesitating, you will need to go richer. If it is a lean bog, more throttle will not help it recover. How to i adust the jet screw ,whether i want to turn clockwise or anti clockwise.
The first step is to determine if you have an AIR screw that meters air, or a FUEL screw that meters fuel. Try to to lean the screw its not helping. Got mine from eBay $10 shipped idk the brand but just like tusk. Just as i had thought the mixture chnage made no difference.
Should I just disregard the manual? So I never worked on bikes carb, cleaned carbs. Sweet, Thanks man.
I know its between here and 2 1/4 because at 2 1/4 with choke it hydrolocks when i try to start it and thats obveously not right lol. What is your setup here? Do Not Sell My Personal Information -, By logging into your account, you agree to our. Adjust the fuel screws and note how many turns out. Try the size up you have and see what happens. You really know your stuff! So i installed it per the manual. to find these in excellent condition and per factory specs; spark plug in acceptable condition; replaced fuel line; completely rebuilding carburetor with new primer, changing main needle jet to slot 2 and slot 4 of a 5-slop jet adjustment to see if performance changes; and verifying that air cleaner and exhaust system are not restricted. I dont know if drilling the hole is a good idea or not. Sure, what specifically? October 28, 2009 in Sport ATV. they also have drive belts that last forever. It may be hidden under a welch plug or cap. Air fuel mixture screw is out 1.5 turns.
Its impossible to adjust stocker. It runs better without the air filter, and also if I turn the screw out the exhaust starts to smoke heavily. I have read a few carb books over the years and it was always confusing. With the 17.5, is the screw responsive? The engine side passage is further trimmed or metered by the fuel screw. I have dismantled and inspected the carburetor three times to check for other potential carburetor problems with jets and passages. The Fora platform includes forum software by XenForo, VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada, grizzlycentral.com is an independent Yamaha enthusiast website owned and operated by VerticalScope Inc. Thanks. Thanks for advice. Get back to me on what you have. They work opposite of each other so it is important to know that before performing this procedure. Thanks! Now heres a question. I found that my pilot screw needle hole is bigger. I recently purchased a 2000 Honda Sabre VT1100C2 with 16000 miles. Idle is fine however when i drive it if i ease the throttle it boggs if i open the throttle on full it just perfect what do you suggest stock pilot screw is 40. The screw with white thumb adjuster knob on engine side, is the fuel screw, and stock setting is 2.5 out. https://www.youtube.com/watch?v=FDRg49vzdxk. and if I screw all in, the engine will dies. What year make model? Hope you can help. Here is some reading: http://www.dotheton.com/forum/index.php?topic=29838.15.
So could my idle be set to high and cause samething? And out if I go any further than 2 3/4 it idles rough and 3 or further it is about to stall. I have a 2005 polaris predator 500. I too have some small filters on, but have a aftermarket exhaust with more flow through. And its not that my bike backfires at all, it actually doesnt ever backfire, its that when I give it a good long rev itll settle down quickly but when I give it a short rev the rpms "hang" before it settles down to idle. Its odd that you get 2 turns out with 17.5, and 5 turns out with 15. So Ive changed the pilot jet leaner to 15. Ive got an 85 GS700 that I have personally rebuilt the engine on 2 1/2 times. Since my last post it has been to cold to ride until today so i went out and went a half turn more fuel. would a overly-rich pilot FUEL screw offer the following symptoms: I was always under the assumption that carbs our of sync would lack throttle response and I always though it was very responsive. After idle, number 4 plug is petrol wet when pulled. Yes i did do a pressure test and all was good after that one little hiccup. Secnodly, I have a problem.
But wheni i pull throttle a little bit in idle to cca 2-4K RPMs, and release throttle, the RPMs are going slow to normal. Also, can you send me a link to the jet kit? Any ideas or suggestions would be greatly appreciated. What do you think?
Rev engine in neutral and note how RPMs return to idle. But I have a carb problem that no one cause solve!I have a 1985 CB700SC with low miles. Carb synch is most important at idle and least important at WOT. Is the carb clean? If I cant fix it myself, I dont want to keep it.
Advertising - I have acquired this ATV not knowing the operating condition other than it has been unused for several months. To verify, remove the screw and it it has a blunt tip then it meters air. I have some questions for you: 1) looking at this link ( CARBURATOR OEM KAWASAKI ZRX1200R), https://www.kawasakioriginalparts.com/road-bikes.html?blockref=99912-1179.C-10&machineid=660&year=2005&model=ZR1200-A5H&country=XX. Just an update. I purchase an 81 Suzuki gs450, I can get the motor to idle without full choke on the previous owner took off the stock exhaust and added an aftermarket system with out baffles. Dellorto PHF carb, 52 pilot, air screw 2,5 turns out for ideal throttle response. So Im hoping to just adjust the mixture to fix it. Vintage Machines.. Pre 1975, Dirt bikes, ATV's, MiniBikes, Snowmobiles, etc. Side x Sides / Sport and Utility Discussion. Thanks buddie. Runs good. Should I buy larger pilot jets? Do you feel like trading a beer for a diagnosis? Ran amazing. Im wondering if that diaphragm has a hole in it. Do you always run VP110?
JavaScript is disabled. I cant seem to adjust it. I like to take 3-5psi of air and blow into fuel inlet. One correction to your otherwise excellent site, the Mikuni VM series carbs have both a pilot fuel screw and pilot air screw for tuning the idle circuit. I tryed to set the mixtures and it was all over the place 1/4 turn idle up. 2003 Polaris xc700 2 stroke. You should follow the rest of my suggestions and you will see that it will run great (1 & 3). Temp is 70 degrees here and the temp at 60 down the highway was about 170-180s and in town it would creep up to 200+ one thing I did notice is that I was able to slowly ease off the throttle without it bucking and kicking and it was much smoother at cruising speed in 6th gear at 60 giving like a 1/16th throttle. Trying a 1/4 turn more fuel tomorrow.
I put in the next size bigger pilot jet (17.5) and it made it run quite a bit smoother. And need help. Thanks again. I had a 62 and 70 slow jet. Put it all back together and fired it up. Bikes are lean from the factory period. also (engine side) Fuel mixture screw does not seem to make any difference at all even fully seated or out 7 turns. The fuel screw setting at idle trims the pilot fuel, and considering the fuel screw ends up at 1.5/1.75, the 1/8 throttle position (all 100% pilot flow) will be rich. So here are my findings. The hesitation, is it a bog (lean) or rich (sputter)? His pilot needle only sticks out about 0.5 mm when close all the way in, but mine is about 2mm out of the hole. What does the plug look like after idling for a few minutes? Let me know what happens when you get the tps working properly. Hey Saber6, i was just adjusting my fuel screw and air screw last weekend because my bike does not idle and when starting it, it spits and spudders. These require special fuel filters and special designed fuel lines.