Sandblasting plugs and idle question????

[cwdhunter]

trying to jet my 1990 rm250 jetted correctly and am using alot of plugs, can i lightly sandblast the ngk iriodium type plugs?

also i replaced the top end, cleaned carb, new air filter, new boysen power reeds, needle clip set to middle spot, checked clymer book, all original jets and needle installed in carb, but cannot get bike to idle, and is a bear to kickstart...will start up by rolling down a hill, and when it does run.....runs great...but cannot get it to idle...(i think if it could idle, it would help to kickstart easier)...set air screw at 1.5 turns out, then tried adjusting to idle, no change...no idling......what can I try next? thanks!

[Louis]

Hmm, any RM experts on here?

[spyderrocs]

you could use one of those air powered plug cleaners. and it sounds like you have a air leak.

[cwdhunter]

idea....could i adjust the slack in the throttle to help bring the idle on......i have about a half inch of rotation till my throttle starts reving the engine...then maybe i could play with the air screws?????????what you think?

[oldfart1958]

In an earlier post I made asking the same question about idling on my RM 250, 1976. I was told to check for air leaks with brake cleaner. Which I havn't had time to do yet. Spray the cleaner around the head, the air intake, the carb, while it is running. If it revs up or runs on idle then there is a leak wherever you sprayed. Be sure to just spray in small areas or you wont know for sure where the leak is.

It sounds like an air leak could be anywhere, but since you did the top end I am wondering if it is in the head. good luck and let me know what you find.

[ElBandito]

Didn't quite get why you wanted to clean the plugs, are they black ?
then a air leak would be unlikely.

If it looks like the bike runs rich (at idle) I would suggest you check the float height.

Floats, float-needle and needle seats are known to deteriorate on OTR/MX bikes

[spyderrocs]

if its not idleing i bet its a airleak on the head gasket. if its fouling plugs and not idleing its not tuned right.

[ALLEYCAT50]

First try a new plug if you haven't yet NGK B8EGV .024" GAP IS STOCK.how does the bike run 1/4 throttle + once the bike is running? float height is something I would check, also while you have the carb apart make sure the needle valve assembley is not worn. if you are still fouling plugs once your floats are set there is a good chance that jetting is too rich. i would check the above until Dave posts on this thread. with a rm250 most people say to jet the pilot one jet smaller than stock move the clip up one from stock. unless you own a 2003 as I have found out the hard way.

[Knoc]

if its fouling plugs, I can see how it would be jetted correctly. Obviously its running to lean or running to fat, which is controlled by the jetting. What main jet are you using? What plug are you using? Ya can try a warmer plug if fat, or a cooler one if lean.

[cwdhunter]

well finally i am happy with the jetting.....I moved the clip on the needle up...to the second position from the top (making the bike run leaner) and it cleaned up the sputtering by 90 percent. In every gear when I gun it I get very little if not any sputtering or hesitation. Then I started playing with my air screw and finally could get it to change the idle.(i have never been able to do this till now)....got the bike to idle nice...shut it off....checked the number of turns, and the air screw is set at exactly 1.5 turns out like it should be. Thanks everyone for the help.....Does this make sense what i am seeing?

thanks alleycat, you were right on the needle clip position, wish I would have tried that sooner.

[ALLEYCAT50]

I am glad you got it. not sure how the weather is changing where you are, but if it is getting colder and less humid, you might want to watch the plug. If the jetting is close, it sounds like it is, on colder days you may have to turn the air screw in (richer) to compensate for the temp and air change. 1/8 of a turn will make a difference.