Eratic Idle

[hak231]

I just tried searching all old posts on this subject, but I couldn't find a sloution to my problem.

I recently removed the PWK 39mm from my stock jugged engine to see what type of jetting it had, because it had a dead spot off idle. I purchased the bike about 2 months ago and I was just trying to understand what the make-up was. After re-installing the carb it now has an eratic idle. It was at a high idle after replacing the carb for the first time, so I tried adjusting the idle screw. That just made it rev high-then low, high-low.

I have removed and re-installed the carb 3 or 4 times, replaced the throttle cable, switched needles, played with idle adjuster, air screw, and replaced the intake to carb boot. Nothing seems to help it. The throttle plate seems to be pretty loose in the body, will that pose a problem?

I know that some here is going to tell me to check the engine for air leaks on the seals, but the problem only occurred after I removed the carb. It seems to be a related problem.

This is the set-up on the bike as I know it.

1987 stock jug with mild porting
FMF fatty pipe
Rad Valve with Reed spacer
No-Lid Airbox, Uni filter
PWK 39mm 185main CEL needle-middle position, 50 Pilot, Air 1 turn out

Also with this new throttle cable, I don't have a threaded connection to go onto the cap, anybody know why?

[GOTFEAR]

look at your reeds and see if the corners are chiped or cracked and make sure no water in gas

[hak231]

The reeds are in perfect condition. They are nice and pliable with no chips or cracks. The tank has been drained and refilled with fresh 93.

Would the throttle valve cause the problem if it was vibrating and letting more fuel/air mixture in?

[dsaint77]

if it was a snowmobile I would say that you had a leaking crank seal.

you have any oil deposites on the stator sidecover?

[hak231]

I just pop-off the side cover and there is no oil anywhere. I added the reed spacer just B4 this problem started. But I did use new gaskets on both sides of the spacer.

[XCredrider]

it almost sound slik ean air leak. my uncles KX500 had a leaking base gasket and it did this same thing. Check for an air leak then go from there.

[dsaint77]

Originally posted by XCredrider
it almost sound slik ean air leak. my uncles KX500 had a leaking base gasket and it did this same thing. Check for an air leak then go from there.

ya that is what he said he did. Normally if its stator side it will suck air. if its clutch side it will burn oil.

It could also be a base gasket or possible around the intake but that is less likely.

is your bike jetted correctly?

thats a very important thing too!

[hak231]

The jetting was never changed from the time I first pulled the carb off. After messing with it for a while, I decided to switch needles to lean it out. Mid and WOT are fine (dark brown with a little wetness) How can I check jetting on the low end if it wont idle?