250r carb question

[Chevy454]

We have a 265 PDR National engine, 35 AS carb, pipe, carbon reeds and spacer, stock filter w/ out lid, etc. Compression is 180, runs out good, but we cannot get it to idle. The idle screw is all the way in, and turning it out does not help, nor does turning the air mix screw. We have tried changing jets, moving the needle clip, but nothing helps. Seems to be on the rich side, at least on the low side.

[wilkin250r]

A really easy solution is to use the throttle cable adjustment near the thumb throttle to pull the slack out of the cable and hold the slide just a tad open. Lots of people do this.

The more complicated solution is to figure out what's wrong. Have you done a leak-down test?

Moving the clip won't help at all, the clip position only affects mid-throttle area, not idle. Nor will changing the main jet. You need to change the PILOT jet, and the air screw. Have you checked the plug at idle? What is it telling you?

[Chevy454]

I have considered doing that with the throttle, but would like to find the problem. Have not done a leak down test as of yet. The plug at idle seems to be telling us rich, but hesitiant to keep lowering the pilot jet in fear of leaning it down and hurting parts.

[Dave83]

How many turns out is your airscrew?

[jas250r]

How do you check the pilot jet? What does it contol? just idle or more? I thought it was up to 3/4 throttle. This will help out with me trying to set my carb up for a 30 over motor with no port work running a 38 pj.

[powerslider]

Drop the pilot jet size to lean out the idle circuit and it will idle fine, I've changed all mine on the airstrikers to smaller than what they came with. Mine wouldn't idle well either until I dropped the pilot size....

Pilot circuit affects primarily the idle to 1/4 throttle range.

[wilkin250r]

Originally posted by Chevy454
I have considered doing that with the throttle, but would like to find the problem. Have not done a leak down test as of yet. The plug at idle seems to be telling us rich, but hesitiant to keep lowering the pilot jet in fear of leaning it down and hurting parts.

The problem with lean jetting is overheating, or possibly lack of lubrication, as I am sure you are aware. However, you may not have thought in-depth about the situation you are in.

At idle, your engine is running rather slowly, so lack of lubrication isn't a big issue. You really have to starve it for a long time before running into problems due to lubrication.

Also, at idle, you are not generating a terrific amount of heat. Therefore, a lean mixture at idle is would again have to run for an extended period of time before causing problems.

You are probably safe lowering your pilot jet size.

You're running a 35mm air-stryker, which is smaller than most people are running, but there are a few out there. Post your pilot size, and get recommendations on what other people are running, to determine if you are in the ballpark.

If you get into the ballpark of what other people are running, and you're still having idle problems, we'll look into other causes, such as air leaks, worn reeds, ect.

[machwon]

Check the carb slide for wear at the point where the idle screw pushes on it. Sometimes they will wear a groove and then you'll be forced to use the cable or buy a new slide.

[Chevy454]

Thanks guys!!!


You're running a 35mm air-stryker, which is smaller than most people are running,

Would you suggest running a bigger carb? We do have a 39mm Keihin.


I had not thought about it, but it would be hard to lean one down enough at idle to hurt parts. I will try a smaller pilot.

BTW, we did get it to idle, I removed the spring, which allowed the idle needle to push the slide up further.

We seem to be in the ball park main wise, the mid and top end are crisp, and the bottom is OK. Just a tad more fine tuning and I think we will have it whipped.

Its been a good learning experience for my son, who will be riding it, to see what is involved with getting a 2 stroke to perform the way it should.

[86-250Rnut]

what size carb where on the stock R's?
thanks
mitch:macho

[honda350r]

Originally posted by wilkin250r
A really easy solution is to use the throttle cable adjustment near the thumb throttle to pull the slack out of the cable and hold the slide just a tad open. Lots of people do this.




I don't recommend doing this old trick! It can prove to be dangerous if the throttle is opened by moving the bars left to right .. You need slack in the cable !!

I agree with Powerslider on this one,no matter what size the carb is !!

Stock carbs are 34mm ..

Jim

[machwon]

You do not need slack in the cable, or its dangerous. The throttle may open up by turning the handle bars if your cable housing is like wedged between the frame and gas tank. Just make sure the cable housing is able to move and not stuck or wedged between other parts. Otherwise, excess cable slack will only result in you not being able to run wide open throttle! Its always a good idea to check the cable and the ability to hit WOT when messing with that stuff.

As for the idle spring screw, without running that you will lose the idle screw. I'd suggest try using a jam nut on it if possible, so it stays in the carb.

[EXtreme-]

Originally posted by Chevy454
We have a 265 PDR National engine, 35 AS carb, pipe, carbon reeds and spacer, stock filter w/ out lid, etc. Compression is 180, runs out good, but we cannot get it to idle. The idle screw is all the way in, and turning it out does not help, nor does turning the air mix screw. We have tried changing jets, moving the needle clip, but nothing helps. Seems to be on the rich side, at least on the low side. I've got ten bucks...say's your too lean. I just went thru all this with a brand new 35 a/s. My motor is only 20 over, 21cc dome and running 170lbs. The stock jets out of the box are 160, dek, 48. I had to bring the main all the way down to a 145....the needle needed leaned to the #2 clip, but THE PILOT WAS WAY LEAN. I threw in a 52 and it's just a tad rich. I need to try a 50 for a final run and see what works best. Then, your idle adjustment screw for the slide should make a difference...mine did. All of the above was done on a dyno machine usning an air/fuel ratio test.

[Chevy454]

I was still rich, no doubt about it. Plug was black, sluggish with lots of smoke on the low side, and not real crisp on the top, with anyone who knew 2 strokes saying the same thing, FAT. Was going to go smaller on the jets, but got to thinking. Maybe the bike needed more air, not less fuel, so I slapped on the 39mm, 180 main, 50 pilot, needle next to top slot. Bingo! Did a plug reading on the main (hi-speed then kill) looked good. Now the quad sounds and runs like a 250r should.

Put the spring back on the idle needle (cut in half), now we have a nice idle, with adjustments either way.

[370kingR]

I think the 38 air stryker is the best carb for that motor. Not as good down low as that 35 will be but better everywhere else for sure. I suppose it all dependes on where and how you ride.

I hate carb problems, i just chuck them and get a new one just because i hate dealing with the constant nonsense of trying to figure out why its runing like crap even when everything is right on it. 38 a/s, dgh needle middle clip, 170-180 ish main, and a 38 pilot i believe...its been a while since i had my 250r.....i miss it :( but i still love my 550r!