Hi,

Can anyone offer advice please?

I have overhauled the carb - Mikuni - all parts renewed, the quad started first time, which was a big releif! However once warmed up the engine is loosing power and won't idle. My question is this, when hot is the carb set too rich? If so is the mixture adjustment the screw/jet on the underside of the bowl? Any suggestions on a good starting point for adjusment would be great

 

Fuel screw is under the carb towards the engine. If you have a small flat screw driver,turn it in counting the turns. Then out to 2 turns as a base setting. Not a bad idea also on checking valve clearance also when cold. If valves are too tight they can tighten further when hot and cause rough idling or cause it to die.

 

Thanks for the information, your advice is greatly appreciated!

I think the valve clearance is ok as before the carb developed a leak due to the needle valve the engine ran great. Do you think i need to weaken the mixture? When turning the screw from the baseline i guess it is only very small adjustments to make?

 

Just let the engine warm up,turn the screw in slowly from the base setting and you can tell if the idle speed increases or decreases. Then slowly turn out and see where the highest idle speed is. Depending on engine final setting could be between 1 1/2 to 3 turns out from a lightly seated position. Then see how it takes throttle. You may have to do this several times. This screw basically affects the idle and up to 1/4 throttle. If you still have problems recheck your work on the carb and the float setting.

 

Thanks, I'll give it a try.

 

Hi, my problem seems to be getting worse! I have had the carb to bits again to check things out, everything seemed in order but still no improvement so I took off the carb again - I'm getting pretty slick at this!! - and put all the old parts back apart from the needle valve which I know was the start of my problem, the engine starts ok but as it warms up it starts the rough running again. I thought ok lets go back to basics and took the air cleaner off to check it out, oh dear! The air cleaner had 2" of neat fuel in the bottom - HELP!!! now i'm stuck

 

Saturated air filter could have been from the original leaking needle and seat. If you've just noticed this,just replace/clean the filter and adjust the carb again and see how it does.

 

Thanks, do you think that this might be making it run rich, the plug is sooting up badly, also i noticed that the air cleaner inlet (under the seat, just behind the tank) is blowing air out, this is how i noticed the fuel in the air cleaner, it was spraying out of the air inlet?
Thanks,
Tony

 

Couldn't help but run rich if the air filter is soaked with fuel! Plus if you said air is blowing out of the air intake tube, I'd still recheck the valve clearance also.

 

Will do thanks, have you any idea of the clearances? Tony