Idle Not Steady 250SX

[sweetip2000]

I cant seem to get this damn carb to idle steady. Weather has been mild in the 20's at night and 50's in the day.
I have a clean air filter. Good flow on vented gas cap. Carb was thoroughly cleaned inside and out. I checked all the boots for air intake and no rips or holes. Stock jetting. Stock settings. Only thing left I can think of is the air intake where it mounts to the motor. Last time I checked that no cracks. I had the same symptoms when I test drove the bike before I bought it. All I did was remove baffle at end of pipe. Same problems after removing baffle. Stock head pipe and exhaust. Is there a way to do a vacuum test to see if this thing is leaking air on intake ? I am tempted to remove the entire air box and boots and go straight off carb with a shorty air filter. Sometimes when I shut it off I can hear a very mild backfire. Otherwise than that low mids and highs it runs like a scalded dog. Let me hear your take on this as I am stumped. Thanks

[redsox]

spark, spark, spark?

[shortline10]

Adjust the air fuel mix screw while its idling for the best and highest point of idle and then turn the idle screw down for the best idle . These motors are 30 + years old and the factory specs and today's fuels will be different .

[barnett468]

.
Also, at idle, spray flammable brake cleaner with the long nozzle attached, very gently around the intake boot where it meets the head and around the outside of the boot and where the carb enters the boot . . If the rpm goes up, you have an air leak.

Since your bike tuns like a "scalded dog", it suggests to me that it might have a lot of high perf engine mods and if this is the case, it might not idle very well no matter what you do.
.

[Jmoozy27]

Check for exhaust leaks at the head. You may need a new copper gasket. Also you may need to go up on the pilot. I think stock is a 38 and a 40 may allow it to idle better especially if you do the intake/exhaust mod that you mentioned.

[Chopsaw]

Choke system hooked up and in good working order ?

[jeswinehart]

Choke system hooked up and in good working order ?

I've had lots of trouble with those fuel enriching valves (Hondas fancy name for that kind of choke system).
Perhaps that small passage is slightly blocked ?

john

[sweetip2000]

I will keep checking, thanks for the feedback. The motor is bone stock and has about 20 hours of usage on it. I would rather have these problems then have EFI with sensors and a shop full of part changers that don't even know how to read their own codes.

[Chopsaw]

I've had lots of trouble with those fuel enriching valves (Hondas fancy name for that kind of choke system).
Perhaps that small passage is slightly blocked ?

john

I was thinking not shutting off , to rich at idle .

[Dirtcrasher]

Andy, OEM exhaust that you removed baffle??

Does it run well otherwise?

Air fuel screw - Has to go in this order - screw,spring,washer,o-ring. If the oring is gone or bad or doubled up, it won't help much.

Start at 1.5 turns out after you lightly bottom it. Screws go bad as well from bottoming too hard......