88 250R with fatty pipe, air box lid off and K&N filter will not idle and would not idle before all of these mods were added. New spark plugs make no difference.

This is a stock 34PJ Kehien carb.

Just off idle, the motor runs great and is jetted properly on the high end.

I have completely cleaned and inspected the carb and all components of the carb, with solevent, carb cleaner and air. All passages are passing air when I blow air through it.

- Idle screw adjustment has no affect.
- Stock slow jet is 42 (I have had a 40, 42 & 48 in the slow jet with no affect)
- With each of these jets. I have had the air screw from 1/2 turn out to 3 turns out, WITH NO AFFECT!!

Other than this, the quad runs pretty good.

Thanks for the help.

 

This may be a silly question, but since you didn't mention it in any of your other adjusting efforts, what about the idde adjustment itself; this screw is sometimes called the throttle stop screw & controls the idle independantly of any air or idle screw adjustments. Since you said the problem existed prior to modifications, was the idle perhaps disabled by turning the idle out?

 

it could be a vacuum leak---try spraying some wd40
around the carb to air box boot, where the boot meets the carb, then spray it is around the other side of the carb, where the other boot takes off
toward the motor---do this while its running of course---if there is ANY change in idle speed, up or down, then you have a vacuum leak, and it wont idle properly--

 

Maybe your throttle cable is stretched out. Is all of the slack out of the thumb throttle cable? Adjust the free play.

 

TRCAGLE is on the right track, I think. But spray around the reed valve gaskets also. Sure sounds like an intake air leak. You might inspect the reeds also - no cracks & they are seating back on the valve. Does the quad run great otherwise - good power & good compression?

 

I did try adjusting the idle speed screw (on the choke ****) all the way in and all the way out. The honda book says the idle screw out provides a larger path for the air and fuel, in throttles it down. Regardless, I have had it all the way in and all the way out to no avail.

I will try spraying the carb boot and reed to see if it is sucking air, that is a good suggestion...but if it is sucking air, wouldn't that lean out the mixture and make it idle too high?

I did change all of the gaskets between the reed cage, spacer and intake boot accept for one that looked in good condition. I will change that and try the spray technique to see if it is sucking air anywhere in the circuit.

I am almost convinced that the air bypass in the carb for idle circuit is clogged, but I cleaned the heck out of it and it appeared to be passing air with a blow gun.

Thanks for the ideas, I will give them a try.

 

Just wanted to comment on your delimma. I am a religious user of my torque wrench, however at my last rebuild I made a SMALL mistake. I accidentally torqued my base studs 6 ft/lbs LOWER than they were to be maxed out at. I started the "R" and low and behold it wouldn't idle or start for that matter without a little dose of the throttle. Before I tore it back down, I meticulously rechecked ALL EXTERNAL steps and re-torqued the four base bolts. I had the torque wrench NOW set at 35 ft/lbs and the nuts snugged down again. The ol' girl fired up and purred like a pu---uh kitten! It may very well be in the carb but check the SIMPLE THINGS FIRST. I really think that it sounds just like MY AIR LEAK. Good luck!

 

Fixed, thanks for the help. I inspected everything...except for the idle **** itself, the needle on the end of the choke, idle **** was broken and stuck in the seat.

Idles great.