Please help..26mm OKO on 125 lifan

[DHZ_XR8cing]

I just put a 26mm OKO on my 125 lifan.It has 35/96 jets in it.It will start but idles very rough and wont rev properly without backfiring.I have tried adjusting mixture screw and needle and it dont make any improvement.
I must add the bike ran great with the standard carbie. please any help would be great.hope the video works.1st time i have done it.

DHZ125 :: DHZ125.mp4 video by DHZ_XR8cing - Photobucket

 

[sean01]

ok, sounds a little weird but id be stripping the carb to bits and blowing out with air.
its possible that while they were changing the standard jets out some sht got in there...
also im hoping you are running a fuel filter..

also are you making sure the little plastic cable lock in the slide is in the correct way cause if it isnt then the needle will go where ever it wants..

 

[DHZ_XR8cing]

thanks Sean I pulled the carbie back off and found the "o" ring was leaking on the adapter.Got that sorted.Got it ridable now.Its tricky to tune perfect.Had to drop the needle 1 notch. Adjusting the mixture i can get it to either be responsive off the line or have good top end.struggling getting it smooth right through the rev range.got a feelin its a jetting problem maybe??

 

[sean01]

shouldnt be a jetting problem..
keep trying mate youll get there... they can be a pain in the a$$ on a small engine

 

[DHZ_XR8cing]

thanks mate.Racing tomorrow and test running it in the dark has been a bit dangerous.Ill give it a bit longer

 

[DHZ_XR8cing]

nope no good,Get it running responsive off the line but boggs down very early in the revs.
Move the mixture less then a 1/4 turn out and no bottom end but revs out good.has me stumped..
mixture screw is about a turn out.any more than that and it wont run properly at all.Still runs with the mixture wound all the way in but rough.

 

[thump*140]

96 main jet will more than likely be the problem... found mine to run best with a K92 main jet on the 125...
perhaps try dropping the needle again

 

[DHZ_XR8cing]

Looks like ill be putting up with it running like a hairy goat tomorrow then.I aint got a 92 jet.Hope some one in the pits has a spare one maybe.Will it be ok to drop the needle again?? It will be on the last slot

 

[thump*140]

yeah that should work ok, basically what it does is slightly reduce the main jet size by proxy....
wont run great, but it will help...

 

[DHZ_XR8cing]

It definatly is quicker now then with the standard carbie by far but i got to keep the revs up,if i labour the engine it has no response at all.

 

[sean01]

a 96 main shouldnt infuence the overall performance too much, it may just get slightly boggy right up the top (anything more than 3/4 throttle)
and when yr racing its not too often that you would use full throttle..

but it does sound like the pilot is a bit out... basically the engine should still run with 2 turns out on the mixture but best at or around 1.5 turns.. iv found that 1 turn just doesnt cut it..
sounds like you need a 38 pilot..

also did you ever get around to checking the valve clearance..
i did 4 pre-deliveries on new bikes yesterday and all were zero clearance.

 

[DHZ_XR8cing]

hey sean,So you recon a 38 pilot instead of the 36?? I aint checked the valve clearances since I put the OKO on it but it was running perfect with the mikuni on it.

 

[sean01]

if your mixture screw runs best at 1 turn then yeah try a 38
and id be checking the valves just in case, bad clearance can send you round the bend with carb tuning

 

[DHZ_XR8cing]

with the needle all the way down and the mixture screw all the way in it still runs the same. Maybe a air leak some where??

 

[themountain]

The carb is generally too big for the engine...you will get a beard about jetting it perfect...send cactus a PM ...he will figure that out!!

 

[DHZ_XR8cing]

Some people are saying its to big for a 125.
some people are saying its not to big. Im guessing its not to big because it idles great and revs out awsome.Its just the flat spot from idle to midrange.Ill get it sorted. Was just looking for ideas to cut down on my time stuffing around with it.

 

[bigd]

I took thumps advice and went a 35 pilot and 90 main
I found it to run perfectly.
The only thing i found is it pops a little at WOT (but i never get to WOT when riding)
prob woudlve been better off with a 92 main but couldnt find one anywhere
here's thumps post

some say he's old and fat. Others say he tunes OKO's blindfolded with two hands tied behind his back.
What we do know, is that he's full of shit, and he's called The Thump....

OKO26mm will work fine on a 125, i've had pretty good results trying it on both my FYM110 and the 125 Zonger...
Jetting you'll need a K35 pilot jet, and a K90 or K92 main jet, with the needle set on the second clip from the top...
as for actual hp increase, bit hard to put a figure on it, but my 125z in the miniblitz went from being not being able to keep up with much at all, to keeping up with Sneezy and Scotty87's Pitpro 140's nearly everywhere except for out of corners, so the power increase is considerable...

a lot of people will tell you the OKO26mm is too big for a 125, but i found it to actually be quite good, and offered more of a power increase than the OKO21mm i tried on the same motor...
OKO26 FTW...

and thump knows his shit
By the way what color is your plug ?

 

[DHZ_XR8cing]

Thanks bigd Ill take that all on board and do some jet shopping tomorrow.

 

[sean01]

yeah check for air leaks as well mate...

 

[DHZ_XR8cing]

Im not a dumb ass.Well not totally.lol but this problem has made me feel like 1. No air leaks for sure. I have pulled the carbie off and on and it all looks perfect. My only other option would be some gasket silicon on both ends of the manifold but im sure the o ring seals enough.Im chasing my tail.Just my luck to not be one of the guys that buy and bolts on a perfect runner.