odd air leak symptoms. 02 gz250

[tunil]

Hi everyone, first time poster here. im a fairly experienced motorcycle technician but havent had much experience on this 2002 gz250.

The symptoms seem a lot like a simple air leak but not really. It runs fine when i first start it up, no choke, itll hold idle for 10 minutes if i let it sit there. As soon as I take it down the street a mile and back it starts acting up. It revs high for 30 seconds after releasing the throttle and eventually slows down returning to a slow idle, usually stalling. So I replaced the intake boot with a new one as well as the sealing o-ring. Also replaced the vacuum line to the petcock. I did a full teardown of the carb to clean it just in case. New spark plug and air filter too. But it still does the same thing.

This ones got me kinda stumped. Any help is greatly aprreciated.

[tunil]

Update.........I blocked off the air cut valve and still no difference.

I also found out the bike wont run with the choke on at all.

pilot screw setting 2 1/4 turns out
float height is dead on spec
all jets are stock

with the bike running i sprayed carb cleaner all around the carb and intake boots with no signs of an air leak.

engine compression is fine

[5th_bike]

Wow, you already did more around the carburetor than I ever did.

Did you check valve clearance?

And the other thing coming to mind, the fuel line (includes little screen in the tank, I think) could be clogged. You could test the screen part of this theory without taking the petcock assembly out by switching to RES.

[alantf]

Doesn't RES have its own screen, that may be clogged too?

[blaine]

Originally Posted by alantf

Doesn't RES have its own screen, that may be clogged too?

Yes it does.

[Lovewuno]

Did you ever find out the root of the problem? I’m having this issue right now