jetting

[blaster_bastard]

99 engine with LA sleeve 240 kit. stock porting. 34mm carb that came off of a 250r. Fmf Gold Series with Power Core 2. Aluminum CFM airbox and V force 3 reeds. I just put this quad together for my little brother and it starts right up and spools up very nice, but once in gear it'll sputter at a higher RPM. what jets or neddle position should i be in? This quad feels like its got tons of power because it'll launch GREAT but then sputter and backfire. HELP

 

[01blaster_freak]

Check your plug after you run it will it sputters an see if the plug is black an wet. if so it's to rich.

 

[blaster_bastard]

is that something that would involve jetting or just play with the air/fuel mixture?

 

[dirtyblaster]

its jetting, whats your premix? jw

 

[throttlesteer]

is that something that would involve jetting or just play with the air/fuel mixture?

Jet size affects air/fuel ratio. They are essentially related. Run a bigger jet and you get the richer (more fuel) air/fuel ratio. Run a smaller jet and you get a leaner (less fuel) air/fuel ratio.

From the way it sounds and how you're implying, you're probably too far one way or the other. Best advice is to pull the plug and describe the discoloration of the tip to us. White means lean, black means rich, brown means just right.

 

[blaster_bastard]

im getting the black tip. any suggestions what i should be i should be running. i'll pull the needle today and find out what im runnig. it came out of a running 250r and i have the 240 kit. it shouldn't be that much diff right?

 

[Roccdeezy]

Was the cylinder ported when the sleeve was installed? If not the carb is way too big. Try the stock carb with a bigger main if your not able to get it leaned out. The bogging in the top end is definetly a main jet.

 

[blaster_bastard]

really? but i've heard of lots of other ppl running the same carb size. i'm about to pull my carb and see what im running. hope i can still use this carb cause i'd hate to change it again.

 

[Roccdeezy]

I run a 35mm carb on mine but it has a stage 3 fully ported jug. The airsal jug I have can actually run a 38mm carb. But bigger is not always better because you lose low end with a bigger carb. Some how you have lost your top end and that can only be too much gas. I'm sure you could dial the 34mm carb in. It will just take a little time and a little head ache. Try going down 2 jet sizes from what is in there now and see where that puts you. If worste comes to worste then try the old carb and see how that works.

 

[Roccdeezy]

HEY! does the bike sound like it is trying to shut off on you in the top end, or just bogging. If it sounds like it is trying to die or shut off let me know what year your bike is. It could be the over rev box.

 

[blaster_bastard]

no it starts and idles fine. if its not in gear at a stand still, i'll be able to rev it up and get the rpms high up there, but once in gear and getting ready to go from 1st to 2nd, it'll bog out. it really sounds like a jetting issue right now. im about to go play with it. be back in a few.

 

[blaster_bastard]

ok i just took the carb about and the jets are actually smaller than i thought. its running 48/148s. im not sure what position the needle is. wouldn't know how to check that. i went to a shop a few weeks back and told them about this and they sold me 3 diff jets ranging from 48-52, and 152-165. those arent very close to what its running now.

 

[Roccdeezy]

Ok! Does the bike smoke really bad when it bogs or does it not smoke. If it does smoke is it blue black or white. Because that is a small jet.

 

[Roccdeezy]

to postion the needle you just pull the top of the carb off and move it on the slide.

 

[Roccdeezy]

Throw the 152 in and see how it works. Could be a plugged jet.

 

[Stryder917]

before you do anything major, make sure you turn the air/fuel screw all the way in, and back it out to 1 and a half turns out, then adjust it from there, im not sure what you will need with the jet you are running but, b4 you do anything extreme...just adjust that screw for a while...and you will most likely need a new plug soon...but that is kind of obvious, but, if that doesnt do anything for you, then you can do something bigger that they suggested, but for now, try something more..minor, ok

 

[Roccdeezy]

Well I hate to tell you this but a high rpm sputter is a main jet. Not an idle mixture screw. But anyways. You should know that the idle air/fuel screw needs to be set 1 to 1 1/2 turns out if your even thinking about working on or adjusting carburetors. Which I'm sure you are.

 

[lbwd]

Dammit -- I have a Jetting Guide in the DIY section.
The Jetting Guide - Yamaha Blaster Forum

Read the last post on there, too...