Engine won't idle

panofish · #1 06-09-2009, 11:47 PM

I've read dozens of threads, but I still feel stumped.
Here are list of symptoms for my new build:

1. Engine starts with medium choke and slight throttle only
2. Must hold slight throttle and feather choke to keep engine running
3. Engine will rev with throttle, but is rough at times (because it is choked)
4. If I release throttle then the engine dies immediately
5. If I turn choke completely off then the engine gets weaker and weaker until it dies
6. Adjusting the idle screw has no effect

My best guess is a vacuum leak between the carb and intake?

Goat Herder · #2 06-09-2009, 11:51 PM

If its a Chinese a stroke ? Just turn the screw clock wise on the left side of the carb. Its the one with a spring on it. Just let us know if you need more help . Welcome to the forum !

panofish · #3 06-10-2009, 12:48 AM

Adjusting the idle screw appears to have no effect.

Goat Herder · #4 06-10-2009, 12:56 AM

What kind of engine is it maybe one of use can help more. Don't worry lots of help here you will get help! soon.. Have you let the engine warm up?

panofish · #5 06-10-2009, 01:11 AM

2 stroke chinese engine.
I let it warm up for quite a while... no change.

Goat Herder · #6 06-10-2009, 01:22 AM

Sounds like a fuel delivery issue. Clogged jet at the carb. Float bowl too low. Or clogged screen at the tank. Some trash made it to the carbs fuel line at the float valve. Don't worry someone will pipe in soon. Vacuum leaks make a china's Idle go way up that I have ever seen.http://motorbicycling.com/f4/carbure...build-195.html maybe this can help. sorry you are having a hard time.

panofish · #7 06-10-2009, 02:47 AM

OK... I disconnected the fuel line from the tank and opened the petcock to drain the fuel.
The fuel drained out slowly in about the thinnest stream of fuel possible without dripping. How fast should it have drained?

I would have thought it would drain as if through a thin straw. I removed the petcock... the filter above the petcock looked clean. So the thin flow of fuel was caused by the filter screen, a smaller orifice inside the petcock valve, or something else inside the petcock?

Tomorrow, I will try running the engine with the fuel remaining in the the fuel line (unattached to the fuel tank) to see if there is any difference.

Goat Herder · #8 06-10-2009, 02:50 AM

Try tacking the gas cap of the tank. If flow speeds up ? You will need to drill a pin size hole in the center of the fuel cap to vent it!

panofish · #9 06-10-2009, 02:53 AM

Sorry... I should have mentioned that I did that while emptying the fuel and the rate of flow was unchanged.

Goat Herder · #10 06-10-2009, 02:58 AM

You are clogged somewhere It should make a darn messy puddle quickly! It should flow faster than that . The petcocks clog up very easily , when trash gets to them. Are you sure the screen in the tank is not clogged? They fall apart very easily too! That will clog the petcock. If your kit did not come with one do get a in line filter. I had a fit with my set up . I did away with the tank filter . Then I used a swamp cooler water cut off valve it has a bigger orifice flow channel to it. But thats just me.