26MM carb jetting

hopefully someone has some experience and can tell me if any of this sounds right. ive rejetted my carb probably 15 times in the last 3 days and im running out of patience.

03KLX125L, white bros pipe, no air box lid and a 26MM procycle carb. i can not get it to run right no matter what jetting combo i run. i like to think i know what im doing but this thing is fighting me like no other.

im currently running a 35 pilot and a 112 main with the needle on the leanest setting. i cant open the throttle wide open from idle no matter what jetting i run, thinking its a lack of vacuum.

i got it running pretty well my house which is at about 600ft elevation. took it el mirage in the high desert and it was VERY rich in the mid ranger but still idled great and ran great wide open. went to the leanest setting on the needle which helped tremendously and made it rid able but was still a little rich in the mid range.

now i got home again and its so lean in the mid ranger i can not ride it but it still idles great.

so now my questions, is it flat out to big of a carb for a stock internal motor? do those jet sizes sound close or do i have some issue in the carb somewhere? ive cleaned it twice thinking there might be something plugged. thinking about ditching this carb and putting the stock one back on.

one more thing i forgot which confuses me, the main jet should play no roll in mid throttle power right? everytime i swap main jets i have to play with the needle again. it seems to change the mid range a ton which doesnt seem right to me.

Here's the thing about big carb bores, they will work great at high RPM, they might even idle if you play with them long enough, the problem is they're going to be total crap in between.

Go to a smaller bore or modify the head to flow more air. I'm no carb expert, but this is my gut feeling based on my experiments.

The main jet does effect that range. It basicly effects 1/4 throttle and up. The needle basicly fine tunes the transition from pilot to main (basicly). Being bone stock, I think you are over carburated


another quick question, will going to a stock bore high compression piston help? money is tight (especially to be spending on the little play bike) so i dont want to go through the hassle of boring the cylinder etc.

is that a good quality kit?

I just installed mine. Haven't got to moto it but Megadeth said his was great. I am planning on going to the track Monday so I'll come back with the full report. Check my other post for details. "Home made big bore"

That kit should work just fine.


Did you end up getting that kit? I rode mine this past weekend and it was awesome!

havent touched the bike since making this thread. dont have more money to put into this thing at the moment.

Keep us posted, that kit is cheap!

thats kind of what scares me haha. what did it end up costing with shipping etc? came with everything you needed?

thats kind of what scares me haha. what did it end up costing with shipping etc? came with everything you needed?

$130, came with everything. I might buy another one to have on my shelf...

These are very basic mass produced motors that are used over a large variety of markets. Dont be scared of the fact that they are inexpensive...Not exactly leading edge technology! haha


These are great machines - for what they're intended to do.

They're inexpensive to buy used (new, I'll leave that to someone else to debate). Properly maintained they run forever. Cheap to modify if you're willing to do leg work like BruceD, mostly reasonable if you're not.

Spare and replacement parts are fairly cheap - they've been making a similar motor since 1980, if not before.

Possibilities are as limitless as your imagination and ability.

Compared to a MX thumper which is already as strung out as a meth addict you have nothing to fear.

ok so im ready to buy a big bore kit. is this what i need? http://cgi.ebay.com/SUZUKI-GS125-GN125-big-bore-Cylinder-PISTON-150cc-kit-/140564951487?_trksid=p4340.m263&_trkparms=algo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BIEW%252BFICS%252BUFI%26otn%3D5%26pmod%3D270749300386%26ps%3D63%26clkid%3D1054561084538129928

also, flat top or raised piston?

thinking about throwing a cam in it while its apart, what do others think? i want this thing to run on pump gas (91) and longevity isnt to big of an issue. it might get riden 10 times a year with a total of 300miles. its really just a little go mess around on bike while taking a breaking from the big XR desert tank.

bumping this, really ready to order this time. will i have any clearance issues with the domed piston? Id like the higher compression.

raised piston for sure even then the compression ratio will be on the low side.

I had some friends bring me back 5 of these kits from China 6 month before they hit E-bay. The first one was the flat top piston "not good" So the raised piston is what you want and a cam of some sort (WEB) if you have the $'s

thanks for the info! do you have any idea what the comp ration ends up being? close to stock?

Sorry I've not taken the time to do the math on this combo . I can tell you it's harder to kick over with this kit , not terrible but you know your kicking it over.

And it's definitely a nice power boost. pump gas will be fine and did I mention the price is right .

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