250r fouling plugs during low rpm/idle

[Mack]

I thought I finally had my 84' 250r dialed in but apparently not perfect. When I bought it several months ago I was having some jetting issues and fouling plugs left and right on the top end of the throttle and the thing would rev out of control randomly. I have since solved these problems with the following corrections.

- Jetted it to spec (main, pilot, However after several tests I ended up raising the needle clip one notch to lean it out)
- Eliminated all air leaks and performed a leak down test with great results.

My compression is 10 or so psi lower than spec but I expect some loss in a 30 year old engine.

I now have the thing running consistently great everywhere in the rpm range except the idling side. Dont get me wrong it idles fine but when I let it idle for too long or spend a lot of time on tight trails in the woods where im not really running it hard rpm wise for very long (just short bursts), It tends to foul a plug pretty quickly. I rode for 10 hours yesterday and went through 4 plugs. They all fouled while in the woods on tight trails so my assumption is that im getting too much fuel on the idling/low rpm side of things. What i dont understand is that this is occurring even though I leaned the needle clip and I'm running a stock pilot jet size. At this point, im not sure if I should lower the pilot size or try and tweak the air fuel mixture.

The trike is an 84' 250r, all stock, jetted as mentioned above, brand new boyeson power reeds, running 93 octane with klotz 32:1.
If anyone could offer some insight it would be much appreciated.

-Mack

[82 250r]

You need a needle with a leaner diameter, and maybe smaller pilot.
If it were mine, i would get a leaner diameter and turn the air screw out 2 - 2.5 turns total and go from there.
You may be able to get the leaner needle from Sudco.

[rjs89ia]

JetsRUs.com is where I get all of my carb parts. They're cheap and shipping is awesome.

[sweetip2000]

What oil are you using for your premix ? My RM 125 I had years ago would do the same thing until I switched to a better oil. Too much air intake can mess it up too. If its jetted to spec I would keep the clip where the manual says it should be. Also the gasoline we have been getting really sucks, lots of water and alcohol, I use this stuff called Star Tron Enzyme fuel conditioner. Add a little marvel mystery oil sometimes too. If the plug is still getting wet after all that then break down the carb and clean it really good twice. The alcohol is really gumming stuff up bad. Good luck with the R.

[yaegerb]

the needle clip has nothing to do with your idle circuit. The needle clip is only in effect a 1/4 - 3/4 throttle. Your problem is with the pilot jet. How many turns out is your air screw? When you blip the throttle on idle it should be VERY crisp (no hesitation and return to idle quickly) within the following range: Crisp at less than 1 turn its too small, crisp at greater than 2.5 turns its too big.

[Poco Loco]

Go smaller on the pilot. Are you riding at elevation? Stock jetting is rated for at sea level. Pop off that air box lid for quick results.

[Mack]

Thanks for the response guys,

I'm not sure why the stock needle would be a problem. The R is completely stock and I feel that Honda probably knew what they were doing with the needle they put in it. I'm in indiana so no elevation and temp was 40 to 50 degrees. I am pretty much on the same page as yaegerb just based on the way it was running through the throttle range.


When you blip the throttle on idle it should be VERY crisp (no hesitation and return to idle quickly) within the following range: Crisp at less than 1 turn its too small, crisp at greater than 2.5 turns its too big.

This is good info because I notice when I punch the throttle, it seems to take a little longer than it should to return to idle. i'll play with the air screw but let me get this straight. If I get it to return to idle crisply with the airscrew more than 2.5 turns out, my pilot is too big? and less than one turn out, the pilot is too small? or do I have it backwards?


Go smaller on the pilot. Are you riding at elevation? Stock jetting is rated for at sea level. Pop off that air box lid for quick results.

100% of my riding is mud, water and sand. this idea scares me. :p

[yaegerb]

Thanks for the response guys,

I'm not sure why the stock needle would be a problem. The R is completely stock and I feel that Honda probably knew what they were doing with the needle they put in it. I'm in indiana so no elevation and temp was 40 to 50 degrees. I am pretty much on the same page as yaegerb just based on the way it was running through the throttle range.



This is good info because I notice when I punch the throttle, it seems to take a little longer than it should to return to idle. i'll play with the air screw but let me get this straight. If I get it to return to idle crisply with the airscrew more than 2.5 turns out, my pilot is too big? and less than one turn out, the pilot is too small? or do I have it backwards?



100% of my riding is mud, water and sand. this idea scares me. :p


Yep you are correct in the pilot size check. Try that and see what you find.