Need help with RM 250!

1

1998RM250

Member
Nov 5, 2008
426
0
I've been trying for 6 months to figure out whats wrong with my 01' RM 250, and finally got the jetting almost right...
The past few rides however at about 1/4 tank fuel the spark plugs just completely die! I've tried both b8es and br8es plugs and they don't even really looked fouled, just seems like alot of carbon type buildup. I put a new plug in and it fires up and runs great until it kills the plug! Removed the magneto cover and it was pretty dirty inside, so I cleaned it out with non chlorinated brake cleaner the best i could. Rode it with a fresh plug and same thing, it died around 1/4 tank fuel. Do magneto's go bad like that, or do they just stop working all togather? I don't really understand where to look next, any better way to clean the magneto? Those suckers are expensive, like $300 i seen!
 
F

FLYING.FINN

Member
Mar 3, 2010
26
0
Hi,..you seem to be having a problem many 1996-2000 RM owners are having, (2001 year model was to have fixed this?). Suzuki RM's were producing a "HARMONIC SHOCK WAVE" while the bike was running causing the "ground electrode" on certain sparkplugs, to break off,...or to break internally away from view. The "stronger",..more "e3xpensive" plug to get is: NGK-R6918B-7 . People have also tested thier plug wire,..magneto,..ignition coil...*(also,..the jetting wasn't 100%,..others just needed a top-end rebuild..THEN rejet your carb). Don't worry,..you're not alone! lets hope the stronger plug works out for you,..good luck.
 
J

_JOE_

~SPONSOR~
May 10, 2007
4,697
3
How far from stock are you on the jetting? What's you elevation? How's the compression? What fuel are you running? By "dirty" behind the ignition cover do you mean wet and rusty? There's alot of variables. If you have a fresh engine that passes a leak down test, proper fuel, a clean air filter as well as good silencer packing you can think about jetting.
 
1

1998RM250

Member
Nov 5, 2008
426
0
The bike has a fmf fatty pipe, Vforce reeds, new twin air filter, new silencer packing, and just put new rings in 8 hours ride time ago. I'm running 93 mixed with yamalube 2R, and completely stock jetting with the needle in the 2nd (stock) clip position. I read on V Force's website that you actually jet leaner with reeds which is weird, my bike has been having a boging problem since I got it. When i pulled the stator cover off it was dirty with wet sugar sand, not rusted. With a fresh plug it seems to be getting good spark, and I wasnt having this problem ever before with the plugs dying. It seemed like the problem started when I switched to the br8es plug from the b8es. The guy who owned the bike before me raced in the ama pro supercross and this was his outdoor bike, so you think they would have had it setup right.



 
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C

Chili

Lifetime Sponsor - Photog Moderator
Apr 9, 2002
8,062
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1998RM250 said:
The guy who owned the bike before me raced in the ama pro supercross and this was his outdoor bike, so you think they would have had it setup right.
Click to expand...

Setup right for him doesn't make it setup right for you. I could jet my sons 125 2 strokes perfect for him nice and sharp and if I rode it I could foul a plug because I can't keep it screaming like he could.

My bet is you are still a bit rich and fouling plugs after a certain amount of riding.
 
F

FLYING.FINN

Member
Mar 3, 2010
26
0
1998RM250 said:
1)When i pulled the stator cover off it was dirty with wet sugar sand, not rusted. 2) the problem started when I switched to the br8es plug from the b8es. 3) ama racer so, you'd think they would have had it setup right.



Click to expand...
What do you mean "sugar sand"? ...white crystally muck?,..if so this may mean your case is cracked!...leaking a mixture of motoroil, coolant onto sand/dirt down below. *[cracked case], This would indeed give you the "BOG" you have had.....since you got the bike?..being a racer/professional,..I'd suggest the previous owner knew about this problem? *[Maybe another mechanic with experience in these matters, could step in to help out in this matter as well.]
 
1

1998RM250

Member
Nov 5, 2008
426
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Hmm thankgod its not a cracked case, the previous owner didn't use the gasket
and used gasketmaker crap... Over time it leaked I guess, and the trails get pretty wet here sometimes! It did look a little white in there though on the flywheel as you can see in the pic I attached. The bike also does not suck any case oil, or lose coolant which is weird.
 
F

FLYING.FINN

Member
Mar 3, 2010
26
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Thank god....you had me worried until you posted the pics. Clean up the mess...I use a small piece of 180 grit sandpaper to clean up off any crud,..and seal up the cover proper. How do you ride the bike?...screaming full out on the throttle in each gear,..like the racers....'cause if you don't,..."CHILI" could be right about your jetting not being "quite" there yet.[racing bikes are tempermental...like a woman you gotta have it just so. You just re-did your top-end...so it needs to be spot on for the way you "throttle it"/ride it.
 
1

1998RM250

Member
Nov 5, 2008
426
0
Yeah I stay on it alot, don't really putt around much... seems to load up a bit in the lower gears when crusing around trails though. I would think the way its jetted now with either a 162 or 163 main jet would be a little lean as it is?
 
C

Chili

Lifetime Sponsor - Photog Moderator
Apr 9, 2002
8,062
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If you are running the stock jetting I'd start by dropping the pilot by one jet size. I have no idea your elevation but since you are running an FMF pipe I checked their recommended jetting for that bike and they recommend going down 2 on the main to a 158 Main, leaving the pilot stock at 48 pilot. PC spec'd to drop one on the main to a 160.
 
1

1998RM250

Member
Nov 5, 2008
426
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I live in FL at sea level, and a 158 main seems so small for a 250cc bike? I hear of people running like 170 main jets in some bikes, I dont see how? I'll get the jetting right once i figure out why the plugs keep dying on me. I'd be interested in hearing about this "HARMONIC SHOCK WAVE" though, first i've heard of it!
 
C

Chili

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Apr 9, 2002
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Getting the jetting right after you figure out why the plugs are dying might be impossible if the plugs are dying from rich jetting.

Several model Suzuki RM125's and Kawasaki KX125's spec'd a special plug because "harmonic shock wave" vibrations were causing the groundstraps to break off and grenade the top end. That is not the case with your bike as Suzuki has spec'd the BR8EG plug for RM250's since at least 2001.
 
F

FLYING.FINN

Member
Mar 3, 2010
26
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Excellent recommendations,...but wouldn't you be asking for some "heating" troubles with a 158 main? *(p.s 2001 Suzuki RM-250 came with a #172 main jet,.. "stock")
 
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FLYING.FINN

Member
Mar 3, 2010
26
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1998RM250 said:
I live in FL at sea level, and a 158 main seems so small for a 250cc; I'd be interested in hearing about this "HARMONIC SHOCK WAVE" though, first i've heard of it!
Click to expand...
If it's not your problem,...good,..but if you want to read what I read; on your computer, type in: Does your RM eat spark plugs?-Thumper Talk ...then click on it and read the whole page.
 
1

1998RM250

Member
Nov 5, 2008
426
0
Pretty sure its a 162 main jet stock, but I took a look at that topic earlier and I don't think thats the case with this bike... maybe its time for a new piston and rings again since I only did rings last time?
 
C

Chili

Lifetime Sponsor - Photog Moderator
Apr 9, 2002
8,062
17
FLYING.FINN said:
Excellent recommendations,...but wouldn't you be asking for some "heating" troubles with a 158 main? *(p.s 2001 Suzuki RM-250 came with a #172 main jet,.. "stock")
Click to expand...

2001 RM250 came with a 162 stock.
 
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