I recently had my entire engine rebuilt. Crank, seals, piston rings ect. The shop went over the carb and changed the jetting ect. They say to get a stock air filter, airbox lid and a stock carb. Right now i have a mikuni flatslide, not sure of the size. It runs amazing, but idle is weird. it will idle normal sometimes, and others it slowly creeps up. it never "runs away" it just idles maybe 1-2k higher then it should. Mods as i can tell : FMF gold series and powercore II, bored .60 over, no airbox lid, k&n filter, reeds but not sure of type or if any porting is done, boost bottle. My question is who here thinks i should go back to a stock carb or if i should play with jettings. Also, if i go with a stock carb, will i be able to use my twist throttle and cable and what about the TORS system? any help is greatly appreciated
Idle issue, think its carb related
- Thread starter Stanimal
- Start date
Irregular idle is a gigantic REDFLAG for an air leak. Do a leak down test... Jetting doesn't idle one way one time and one way another time. Jet sizes don't change like that but air leaks do...
air leak !!! you can play with the carb till your fingers fall off and it wont matter. build or buy a leak down tester.
did it with 2 motors, same idle problem. when they rebuilt the motor they used a new set of cases. this shop is VERY VERY reputable and ive used them for years. they race professionally all over the country not just on bikes or atvs but also with cars. They would NEVER let a bike/atv go with a leak. They said the carb is just too big and they think it had a BB kit at one time. Its either a 36 or 38 mm carb i believe. Like i said the bike has done it for the last 5 years ive owned it so its not something new. i feel if it was a leak, i wouldnt have gotten 3 HARD years out of the engine riding it 100-200 miles every week
Your original post made it sound like you just rebuilt the engine and this was new.
If you are running far too large a carburetor, it will make the engine run funny. If you need to trade down to a smaller carb, list yours for trade in the classifieds. $10 a year to become a supporting member and you can use the classifieds unlimited.
If you are running far too large a carburetor, it will make the engine run funny. If you need to trade down to a smaller carb, list yours for trade in the classifieds. $10 a year to become a supporting member and you can use the classifieds unlimited.
I plan to donate as soon as i get home anyway. I dont really want to trade it, ill just buy a stock carb outright. I do plan to eventually do a BB kit IF i keep the quad. Got offered a lot more then i feel its worth and might let it go. Just want to fix the idle issue before it sells.
As you warm up the charge becomes leaner . No way around it. If you can get it back to a normal idle with a slight adjustment of the pilot it is normal
Stock carbs are out there for the taking. Find you one, jet it close for the mods, and see how it does.
I know for sure you can't make any power with the stock airbox with the lid/snorkel on it. It's like trying to run a marathon and breathing through a straw. Even a stock engine/carb will benefit from removing the airbox cover on these quads, with the appropriate rejetting if necessary. The stock airbox cover is REDICULOUSLY choked. That's just plain bad advice IMO.
you should have at max a 32mm carb on that cylinder. But never ever run a lid, unless your running the mud madness or something then no need to run it. Get K&N off your bike and put a uni on it. Buy a 28 or 30mm carb and that sucker will run good. But if you plan to go BBK, still keep that 36 (thats if thats what it actually is)
I dont think the size of the carb is affecting your idle. I had a 36mm on a stockish cylinder and I had no problems getting the thing to idle. In fact, it was so rich it started right up without choke, and idled quite nicely.
I think however, if your float level isnt set right, or theres something screwy with the pilot circuit (maybe a venturi port has gum in it and is clogging up), it will run odd.
Ive also seen issues with throttle cables sticking so when you are revving on it, or coming down off the revs, the cable sticks a little bit and the slide is open more than normal, causing the idle to hang high. So it might just be an issue where you need to adjust the throttle cable.
And its possible the 36mm carb is causing your issues. Its a Mikuni. I dont have any experience with Mikunis, I know with my PWK36 I had no idle issues, I just couldnt get my jetting right, but I know now I was a n00b and wasnt doing it correctly anyway so Ive learned a bit since then.
Pull your stator cover off and see if theres any spooge in there. If theres no spooge in there, check your tranny fluid and make sure youre not using it (usually you know if theres a trans side leak, as you will start burning the fluid and it STINKS. If you dont see anything then get yourself a bottle of carb cleaner and while its idling spray it around the intake manifold (the part the carb connects to), and all over around there, behind the carb, up the airtube toward the filter, etc. If you detect any change in idle after spraying somewhere, spray it again. If it definately changes, you just found an airleak.
This is what Id do.
I think however, if your float level isnt set right, or theres something screwy with the pilot circuit (maybe a venturi port has gum in it and is clogging up), it will run odd.
Ive also seen issues with throttle cables sticking so when you are revving on it, or coming down off the revs, the cable sticks a little bit and the slide is open more than normal, causing the idle to hang high. So it might just be an issue where you need to adjust the throttle cable.
And its possible the 36mm carb is causing your issues. Its a Mikuni. I dont have any experience with Mikunis, I know with my PWK36 I had no idle issues, I just couldnt get my jetting right, but I know now I was a n00b and wasnt doing it correctly anyway so Ive learned a bit since then.
Pull your stator cover off and see if theres any spooge in there. If theres no spooge in there, check your tranny fluid and make sure youre not using it (usually you know if theres a trans side leak, as you will start burning the fluid and it STINKS. If you dont see anything then get yourself a bottle of carb cleaner and while its idling spray it around the intake manifold (the part the carb connects to), and all over around there, behind the carb, up the airtube toward the filter, etc. If you detect any change in idle after spraying somewhere, spray it again. If it definately changes, you just found an airleak.
This is what Id do.
lol thank luni for the advice, already been there with the carb cleaner. im a mechanic by trade, but will be the first to admit i have no clue about setting jets on a 2 stroke. i can tune a holley or equivalent easily, but am lost with 2 stroke tuning. i can play with it im sure and test the plugs each time but to be honest, i dont wanna spend that much time tuning my 4 wheeler. i get $95 a hour to tune cars, so for me to spend that much time on my own 4 wheeler is stupid to me :/. Guess ill be unlazy pull the carb off and measure it find out just what i have and go from there.
its a mechanics nature to learn what they dont know. so take the dame thing apart and learn how to fix it. i find it odd that your a mechanic but had someone build your blaster engine HAHA :-/I:I:-/ come on man its a single cylinder 2 stroke any 95 dollar an hour mechanic should be able to handle such job 8-|
Basic rule of jetting a 2 stroke is first off, warm the bike up before you attempt jetting the idle. Also check your float level too, cause you cant get jetting right if the float is off. Once youve done those 2, your pilot selection should be the jet that makes the idle kick up the highest but not be more than a couple turns out on the airscrew. So example. If you have a pilot in there, and you have to turn the airscrew out 4 turns to get it to idle the highest, youre too lean. Likewise, if you can turn the airscrew less than a turn (some say 1.5-2 turns) to get it to idle, youre too rich. You should have the highest idle 1.5-2 turns out. Anything after that shouldnt affect the idle, and anything before that should bog it down. Once you get your pilot set then check your main. Main jetting is a bit easier cause you can go high on the main, if it bogs, pull mains back till it doesnt bog. Plug chop it, and if its that mocha brown color, youre good. If it isnt, adjust till it is.
The jet needle is the trickiest one to jet, cause you could have good idle and good top end but crappy transition. The jet needle controls the midrange of the bike, and is probably the most important aspect of jetting. There are clips on the needle, lowering the clip down toward the tip raises the needle so it richens the mixture on mid. Likewise raising it lowers it down and leans it out.
Jetting is easy on paper, but in real life, its pretty tough till you get experience of what a lean poppy/boggy engine sounds like, and a rich sputtery engine sounds like. Also, sometimes the butt dyno lies because to a point leaner makes more power, so not always what feels good is what the bike wants.
Hope this helps, Ive learned through some hard times how to jet, and trust me, it can be a biotch, but it is a nifty skill to have, and it WILL save your ass knowing how to do it right.
The jet needle is the trickiest one to jet, cause you could have good idle and good top end but crappy transition. The jet needle controls the midrange of the bike, and is probably the most important aspect of jetting. There are clips on the needle, lowering the clip down toward the tip raises the needle so it richens the mixture on mid. Likewise raising it lowers it down and leans it out.
Jetting is easy on paper, but in real life, its pretty tough till you get experience of what a lean poppy/boggy engine sounds like, and a rich sputtery engine sounds like. Also, sometimes the butt dyno lies because to a point leaner makes more power, so not always what feels good is what the bike wants.
Hope this helps, Ive learned through some hard times how to jet, and trust me, it can be a biotch, but it is a nifty skill to have, and it WILL save your ass knowing how to do it right.
i had someone else build it because of this.... i put new piston and rings in it. Rode it twice then it would run good one minute and have zero power the next. Then it wouldnt start. If i used ether i could get it running and it would run okish. i did all new reeds, new reed gaskets, tore the carb down and adjusted and cleaned dozens of times. The more i fixed the worse it ran until it didnt run at all. I sent it to them because i got tired of wasting my time, they said $60 to tell me whats wrong. All said and done i paid them a hour labor to do a full rebuild including crank, rod, piston/rings, bore, install new gaskets, rejet and i got their warrenty. So i paid them $75 above parts cost to do the rebuild. They also had new cases for me because mine was cracked, and gave me a new shift shaft because mine was bent so bad it had to be cut. I just got TIRED of messing with it when i have money making projects sitting around. I dropped it off a basket case and picked it up a week later running like a champ 
LOL i know the sounds your talking about, we call it snap crackle and BANG . i tune f/i cars with a program called CHROME. I usually go off the a/f ratios but sometimes even they lie to you . If i knew what the a/f ratio should be on the blaster id throw my meter in the tailpipe and go to town.
. i tune f/i cars with a program called CHROME. I usually go off the a/f ratios but sometimes even they lie to you . If i knew what the a/f ratio should be on the blaster id throw my meter in the tailpipe and go to town.
but if you picked it up a week later running like a champ why do you have this post ? B) we all know it takes more then an hour to rebuild a blaster. either way if you have a warranty with it bring it back to them and see what they have to say. its hard to make out what is going wrong with it when your posts are all over the place.
i had someone else build it because of this.... i put new piston and rings in it. Rode it twice then it would run good one minute and have zero power the next. Then it wouldnt start. If i used ether i could get it running and it would run okish. i did all new reeds, new reed gaskets, tore the carb down and adjusted and cleaned dozens of times. The more i fixed the worse it ran until it didnt run at all. I sent it to them because i got tired of wasting my time, they said $60 to tell me whats wrong. All said and done i paid them a hour labor to do a full rebuild including crank, rod, piston/rings, bore, install new gaskets, rejet and i got their warrenty. So i paid them $75 above parts cost to do the rebuild. They also had new cases for me because mine was cracked, and gave me a new shift shaft because mine was bent so bad it had to be cut. I just got TIRED of messing with it when i have money making projects sitting around. I dropped it off a basket case and picked it up a week later running like a champ
LOL i know the sounds your talking about, we call it snap crackle and BANG
13.5:1 ish would get you in the right area.
If you read any of the previous posts you'd see the shop told me it needed a stock carb to idle correctly. I measured it today and im pretty sure they are right and a 38 is too big for what i have. I wont bother posting anymore was just trying to save myself some time.
Similar threads
