OKO 26 on Zonshen 140

[Eyles]

Hi All,

I have an OKO 26 on a Zonschen 140cc it has a 36 pilot and a 100 main as supplied. It runs well right through the rev range but seems impossible to get to idle properly. Regardless of the pilot jet fitted (have tried everything from 36 through to 48). I get it to idle properly then crack the throttle slightly but when releasing the throttle it continues to rev and won't go back to idle as if it is running lean. The slide is not sticking. Any ideas?

 

[user 20441]

36 seems waaaayyy too high! :-O in a 22/24 carb you would put a 17.5 so you got allmost double size?
woudld you have something smaller to try out out and see if that helps idle?

 

[Eyles]

36 seems waaaayyy too high! :-O in a 22/24 carb you would put a 17.5 so you got allmost double size?
woudld you have something smaller to try out out and see if that helps idle?

Anything under 36 and it won't start at all. It just kicks back

 

[AntNZ]

36 seems waaaayyy too high! :-O in a 22/24 carb you would put a 17.5 so you got allmost double size?
woudld you have something smaller to try out out and see if that helps idle?

sounds like you talking fakuni jet sizes, if it runs fine through the rev range then I say the k36pilot isn't far off, oko's need a longer throttle cable, sounds like your slide isn't returning to the bottom....you have adjusted idle screw I presume??...
sometimes if you put your throttle grip on to far it can bind/stick to the throttle housing on the bars....
take your air filter off and work the throttle a few times just to make sure the slide is returning to the bottom, you can also hear it hit bottom when you let go of the throttle, not when running of course.

just a few suggestions, hope it helps...good luck

 

[Eyles]

sounds like you talking fakuni jet sizes, if it runs fine through the rev range then I say the k36pilot isn't far off, oko's need a longer throttle cable, sounds like your slide isn't returning to the bottom....you have adjusted idle screw I presume??...
sometimes if you put your throttle grip on to far it can bind/stick to the throttle housing on the bars....
take your air filter off and work the throttle a few times just to make sure the slide is returning to the bottom, you can also hear it hit bottom when you let go of the throttle, not when running of course.

just a few suggestions, hope it helps...good luck

Thanks for,the advice. The throttle doesn't stick and has the correct travel. What happens is I get the motor to run at an erratic but reliable idle speed but after a run it is almost as if the throttle is stuck at 1/2. After cooling down it is good again. The air screw is only 1/2 a turn out with the 36 idle jet

 

[Eyles]

Idle jet is now 50 with a 104 main and the motor is running well right through the range now and idles well. I suspect there is still a little to be gained at the top end so might try a 106 main.

 

[AntNZ]

Idle jet is now 50 with a 104 main and the motor is running well right through the range now and idles well. I suspect there is still a little to be gained at the top end so might try a 106 main.

holy sh$&balls!!! a 50 pilot on a 140 does not sound right, I run a 39 on my stock 160ho and a 42 on my v2 headed 160ho!
have you checked for vacuum leaks with some crc or wd-40??
was your 36pilot partially blocked??
where is your air/fuel misture screw set at now?
have you done a plug chop to check whether it is rich or lean??

 

[AntNZ]

oh, and are you running an oiled air filter??

 

[AntNZ]

they also suck air in through the cap on the carb and where the cable goes into the brass swivel....

 

[Eyles]

Yes running an oiled oil filter. Have also sealed the cable entry points to the carb. Have dropped the idle jet back to 45 and the air screw is now one and one half turns out. Idles well and transitions well. I have checked all points of leakage on the intake manifold at both the carb and the head and all is good. Motor performs well and runs out easily to 110 kph on a postie with a 17 front sprocket. Will cruise easily at 100kph and I weigh 100kg without gear. Still seem to have the problem of the throttle seeming to stick on at low to medium throttle settings causing it to rev its head off when the motor is hot when the throttle is not actually sticking at all. Perhaps the carb is too big for the motor?

 

[AntNZ]

I've dont have a 140 but I dont think the 26 would be too big, a lot of people run them on 125's without any drama's....
have you checked your plug after letting it idle, 45 still seems too big and you said it ran and transitioned fine with the 36 pilot.
sounds like something is sticking/binding to me, is the needle a little bent maybe??
does the cable have a kink in it somewhere??

 

[Cordogs]

It all sounds a bit fishy to me, my 160 is tuned to perfection with 36/100 jets in my Oko. I would of thought they would be too big for a 140 but I’m no master spanner spinner. But if you have a 45 on there then it definitely sounds like you have an air leak somewhere, erratic idle is a good sign of this.

Have you checked to see if you have the correct size return spring and clip inside the carb? Also have you pulled the carb completely apart and blown out not only the jet housing but fuel inlets too?

 

[Eyles]

It all sounds a bit fishy to me, my 160 is tuned to perfection with 36/100 jets in my Oko. I would of thought they would be too big for a 140 but I’m no master spanner spinner. But if you have a 45 on there then it definitely sounds like you have an air leak somewhere, erratic idle is a good sign of this.

Have you checked to see if you have the correct size return spring and clip inside the carb? Also have you pulled the carb completely apart and blown out not only the jet housing but fuel inlets too?

Yes well starting to get somewhere. Found that the throttle was intermittently binding in its handlebar mount. Pulled it apart, removed all the grime and it is now completely free. Problem one solved. Went back to a 100 main and 42 slow and it now idles well hot, transitions well and pulls hard right through the range. Postie now cruises comfortably at 100kph. Thanks for all the good advice but don't stop now if something else comes to mind.

 

[AntNZ]

what does your plug look lke after idling?,I still think the 42 is too big....
have you read the OKO thread,multiple examples in the first 10 pages of 26's running mint on 140's.

 

[Eyles]

Thanks All for the advice. The problem is now solved. The throttle cable was sticking at the throttle (handlebar) end. That was fixed easily. The new air filter appeared to have been oiled but on closer inspection it was not. I oiled it and now the engine runs well and idles properly with a 36 idle jet and a 104 main. You were all right after all - it was running lean as most off you suspected!

 

[AntNZ]

Thanks All for the advice. The problem is now solved. The throttle cable was sticking at the throttle (handlebar) end. That was fixed easily. The new air filter appeared to have been oiled but on closer inspection it was not. I oiled it and now the engine runs well and idles properly with a 36 idle jet and a 104 main. You were all right after all - it was running lean as most off you suspected!

just so you know for future reference, it was running RICH not lean....you went down on your pilot jet but was def the throttle sticking causing the errattic high idle.. glad you got it sorted

 

[rotn50]

Thanks All for the advice. The problem is now solved. The throttle cable was sticking at the throttle (handlebar) end. That was fixed easily. The new air filter appeared to have been oiled but on closer inspection it was not. I oiled it and now the engine runs well and idles properly with a 36 idle jet and a 104 main. You were all right after all - it was running lean as most off you suspected!

The throttle assembly was too far in causing the rubber end on the grip to touch the bar end?

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