Fouling plugs left and right...need some advice

SpectraSVT · Nov 11, 2002

I have a 93 RM 250 and I have been fouling plugs for over a year now. I got a fatty pipe for it and rejetted it to the recommended settings according to FMF. The plug lasted 6 months so I thought everything was finally fixed. But since then it has fouled every week and recently twice in one day. I just replaced the reeds and adjusted the air screw but after 2 hours it fouled again.

My buddies thought it might be a seal but there is no gear oil on the plug. Is there something I am missing? This is becoming very frustrating and expensive :(

Stew312 · Nov 12, 2002

Could be a left side crank seal, that is the dry side so no gear oil would get onto your plug, you would just lose some compression and cold foul the plug.. That happened to me and i didn't figure it out till 16 plugs later...

SpectraSVT · Nov 12, 2002

So, a compression test is what your suggesting? How do you do that?

agitt73 · Nov 12, 2002

if you are burning gear oil you would not see it on the plug
it would look like a plain old fouled plug
and on the seal thing you would have to do a leak down test
not compression test but low compression could be the problem
also buy a compression tester from your local auto parts store
a good compression would be 150 pounds and up a bike will run
as low as 80 pounds but will be hard starting and lack power

SpectraSVT · Nov 12, 2002

Whats a leak down test?

MikeT · Nov 12, 2002

Originally posted by agitt73
a good compression would be 150 pounds and up a bike will run
as low as 80 pounds but will be hard starting and lack power

Small note here. I ran a compression test on by bike in the Garage when it was cold (1996 YZ125) and I got a reading of 132 or so psi. I thought I needed a top end. I brought the bike to the track and 96whyzee125 pulled out his tester and we did the test when my bike was hot, it then read 165 psi. There is a large variance in psi when doing this test due to engine tempreture. I don't know how to do it, but I believe you need to look at the leak down test.

FIRST off though, I'd pull the carb off and thtoughly clean it out. ALSO check to see if your main jet fell out. I know a certain racer here on the boards who had this happen to him on a 2002 CR 250

SpectraSVT · Nov 12, 2002

Thx for the advice! I'll look into that...

Glitch · Nov 12, 2002

Doing a leak down test, you need special instruments that fit on where the reeds bolt on. Having a shop do it is probably best but I wouldnt do have it done to begin with.
Are you using the same plug, heat range and all? Next time you change your oil, measure it after it comes out and see if it is even close to how much you put in.
Just some suggestions. Best of luck.
Jim

Nevada Sixx · Nov 13, 2002

could be ignition failing also.. check your kill switch for shorts..

SpectraSVT · Nov 13, 2002

I had a couple buddies check it out the other night. There is good compression, carb is clean and all jetts in place, float bowl floats just fine, stator metered as good. they could not find anything wrong with it.

I am gonna start checking the gap to make sure it is accurate; haven't been doing that. I think I am also flooding it at starts but I don't thinks thats entirely the problem. Is there anyway to fully check the stator to see if its an intermittent problem? I am also gonna change out the kill switch for a new one and see what happens. Its hard to tell sometimes...the plug may last for a month or one week so its hard to narrow the problem down.

2smoke · Nov 13, 2002

Bodgie crank seal test.... get puller pull magneto and flywheel off down to where you can see seal. Make visual inspection. Then get soapy water (more dishwashing detergent than water) smear over seal get someone to turn over kickstart look for bubbles.....easy peasy!!!

2smoke · Nov 13, 2002

Oh yeah electrical stuff can check out OK when testing but still be s@#t borrow a good one and put it in is the best.

SpectraSVT · Nov 14, 2002

I figured as much, but nobody else has a 93 and new stators cost $160 which is a bit more than I currently have with X-mas coming up. But thanx for the ideas...gotta try those soon!!

SpectraSVT · Nov 15, 2002

If it was a leak in the seal would the bike still act normal power wise. The bike pulls harder than it ever has since I've owned it. I have been slowly dialing it in and when it works it runs perfect. Just curious

Stew312 · Nov 15, 2002

Yea, I had a blown seal and it ran fine, still could pull the front end off the ground in 5th.. It just cold fouled plugs like it was its job, I didn't figure it out till i pulled the magneto and saw the seal half out of its seat. ha..

2smoke · Nov 17, 2002

Yeah the air leak is actually leaning the fuel air mix so it would run crisper than what its set at. Do you run fresh fuel? I have many problems with premix thats been stored for more than a few days. Oil tends to seperate. Ive had similar problems with water in magneto causing bad spark in certain part of rev range and fouling plugs. If magneto looks like it may have got some water or you haven't been airing it out. Before you buy new try this little spaz trick I got off an electrician heat oven to 400 (celcius I cant convert to farenheit) clean unit and contacts, then heat magneto( leave wiring hanging out door) till its hot to touch (15min or so) and leave to cool in cool dark spot on a towel to cool overnight. I have seen a couple of magneto's dried out and resurrected with this method. .

MikeT · Nov 18, 2002

Dude, 400 degrees Celcius is 752 degrees Farenheit. You sure about that number?? I think the oven would start to melt up there even if you could find an oven to get that hot, which home ovens don't.

Stew312 · Nov 18, 2002

I guess that would be some crazy spaz trick. Is the sun that hot?? ha

MikeT · Nov 18, 2002

Don't know. I melted my termometer last time I tried to check it :)

MikeT · Nov 18, 2002

That would be tHermometer. Sorry

Stew312 · Nov 18, 2002

The H probably got melted off after 700 degrees, not your fault.

MikeT · Nov 18, 2002

LOL!!!

2smoke · Nov 18, 2002

Yeah try 150 degrees celcius 400 where did I get that ??? It only takes 15 minutes if it doesn't work you are no worse off.

Motopainter · Nov 22, 2002

Have you checked your airfilter and airbox for obstructions maybe an old filter with to much oil or wrong type of oil, always check the simple stuff first.IMO

Fouling plugs left and right...need some advice

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