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2003 rm 250 Fouling Spark Plugs/ Rich Bottom End

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I've tried getting help from multiple dirtbike forums with no true results. Bike is a 2003 Suzuki Rm 250

 

So over the past couple months I've been steadily working on the bike. 
New front and rear brake pads, front and rear wheel bearings, swingarm bearing, rebuilt shock linkage. Cylinder resleeved along with a new top end. 

Now let's mention where I left off at in October.
Running 32:1 Maxima Castor 927 93 Octane Unleaded Pump fuel. Bike smoked a lot along with a crazy amount of spooge out of the silencer. Had a rich low end right off idle to about 1/4 throttle till it cleared out. Would load up if not constantly cleared out which is difficult in certain trails my buddies and I ride. Bike had a lot of vibration. Would idle fine when started cold, but once warm it needed to be constantly kept on the throttle otherwise it'd stall.

I checked the crank seal along with the float height and both are fine. I then decided to repack the silencer after rebuilding the top end and having the cylinder resleeved. This time I tried a different gas mix of Klotz r50 40:1 93 unleaded pump fuel at the advice given from multiple friends who currently run the same mix with good results. Broke the bike in and even after multiple long rides she was still pretty smokey, still loaded up, and still had the rich bog at 1/4 throttle. The spooge around the silencer wasn't so bad. So now I'm looking towards leaning the pilot/slide/clip and needle to just clear up that 1/4 throttle bog and hopefully not foul so many spark plugs.
Had a 165 main, 45 pilot, stock power jet, stock needle at 3rd clip 
Rode it like this probably 2 different times and fouled 5 spark plugs total between the two trips. Each plug was black and fouled in low-mid speed riding. My bike didn't ever foul plugs before running 32:1 Maxima Castor 927 93 octane mix in the fall. 
Thinking about trying out the 7.0 slide I ordered, a 42/40 pilot, and the stock needle clip at 2nd/1st slot. I also picked up a 48 power jet I might try.
If this doesn't clear the plug fouling and low end studder I'm going to order a leaner needle.
My next thought if this jetting combo doesn't work out is to go back to stock jetting with Castor 927 at 32:1 and re-jet it from there.
I've read basically every possible article I can find online about the jetting on the '03 rm 250 and everything I've read pointed to ordering a leaner needle along with the 7.0 slide. Also I read that in order to be able to jet the pilot lean enough to be crisp and not ping I'll need to either run a mix of race gas and 93 pump fuel or just race fuel. 
1200 ft elevation riding at 70-90 degrees, Trail Riding along with some track/wide open powerlines

Can someone chime in with suggestions/opinions or their jetting specs for this bike? I just want my bike to run correctly :/

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Tried a 162 main, 40 pilot, 2nd clip on needle last night along with the 7.0 slide and the bike fouled a plug within 10 minutes of riding around. I was opening it up and trying to clear it out too.

Edited by Twosmokeforlyfe

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Tried a 162 main, 40 pilot, 2nd clip on needle last night along with the 7.0 slide and the bike fouled a plug within 10 minutes of riding around. I was opening it up and trying to clear it out too.

 

 

That should totally be in the ballpark for jetting, sounds like possibly you have a leaky RH crank seal.

 

My 03 I run 40 pilot, 7.0 slide, W needle 2nd clip and 170-172 main. No smoke, no spooge, could idle all day without fouling a plug running 25:1 premix.

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Thanks for the replies!

 

I'm going to inspect the crank seal this weekend. Not sure if I should just order a new seal just to make sure that's for sure not playing a role.

 

Is that the N3WK Needle? I'm actually trying to figure out which needle to order now.

These are what I'm thinking now: Jd Jetting's Needle, 01 Yz 250 Needle, 04 rm 250 Needle, or a N3WK/NECJ Needle.

 

Also if you don't mind me asking what's your altitude/premix oil/gas/what/where you ride?

Edited by Twosmokeforlyfe

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N8RW in the summer, N2ZW in winter. N2ZW is just a half clip richer if you like fine tuning, otherwise you're fine with the N8RW. The W needle only cleans up a 1/8-1/4 steady throttle rich stutter, otherwise my bike ran good on the stock H needle.

Those jetting specs I gave you are for 500- 2500 feet, temps 70-90's.

I run Avgas as I run high compression and aggressive timing.

25:1 Amsoil Interceptor.

 

Best test on crank seal IMO is drain and refill your tranny oil with specified amount. Go for a good couple hour ride. Drain tranny oil and measure. Any lost you know you have a crank seal leak.

Edited by tribalbc

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That's exactly what I needed to know! I solved the smoke and spooge issue for the majority but couldn't seem to clear up that studder at 1/8-1/4 throttle along with fouling plugs.

 

I'm going to try to get it jetted correctly running Klotz R50 and if that doesn't work I'm going back to Castor 927. 

Also, would you recommend interceptor for trail riding and WOT powerline riding?

 

Thanks again! Hopefully this will resolve my problems.

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Interceptor is perfect for your needs. I use it for a mix of trails and MX. Clean burning, PV and piston/head are sparkling clean on rebuilds and its cheap.

I'd say the only negative is it's dye free so you can't tell when the gas is mixed. You must be diligent with your mixing/ storing as you can't visually tell if the gas is mixed. 

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Do you think I should go back to stock jetting or at least richen it up a bit going to 32:1 interceptor from 40:1 Klotz R50 now?

 

 And do you think running 93 octane pump fuel is fine for bikes motor being all stock other than pc pipe and silencer?

 

 

Seriously though, thanks for the help!

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Do you think I should go back to stock jetting or at least richen it up a bit going to 32:1 interceptor from 40:1 Klotz R50 now?

 

 And do you think running 93 octane pump fuel is fine for bikes motor being all stock other than pc pipe and silencer?

 

 

Seriously though, thanks for the help!

 

 

32;1 from 40:1 isn't a huge change in AF mix. Nothing more than a temp humidity swing day to day. Try it first then make the call on rejeting.

93 should be fine, but some bikes a shot of Av or race gas mixed with your pump is needed. Are you getting any Detonation? What did the piston and head look like at rebuild? 

Not a big fan of the PC pipe (have one) on this bike though I do like the silencer. Prefer running the Gnarly with the PC silencer. Much better bottom end is woods is your thing. Another great mod for you is a 10 oz FWW. The cranks are very light on these 03's and Suzuki added weight every year right up to 06 when development stopped.

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Have not been getting any detonation, I just remember reading something that said in order to jet it crisp down low it needed a higher octane fuel.

Piston and head looked fine with little to no wear and tear. Powervalve was pretty gummed up though.

 

Needles you suggested are on the way.

Once they arrive and I have a day off work when the weather's nice I'm going to take a couple hours to finally get the jetting right.

 

My throttle is kind of sticky on my bike so I think I'm going to buy a whole new throttle assembly. Do you think I should go ahead and order a new throttle cable along with it?

I should be able to run my bike on Klotz R50 32:1 as multiple friends of mine do on their 250 two strokes and I ride just as fast if not faster.

 

If I can't find a solution to the plug problem I'll try testing my ignition coil/stator and replacing my crank seal. And if all else fails I'll go back to Castor 927 and deal with the fact that If I don't ride it hard enough I'll spend time cleaning my powervalve lol

 

Also I'm wondering do you have a lot of vibration in the handlebars on your bike? Mines pretty bad seeing as my hands are sore after a couple hours of riding.

Edited by Twosmokeforlyfe

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My RM gives me less vibration than any 2 stroke I've owned I'd say. So that and your pic of that fouled plug leads me to believe bad crank bearings causing a bad RH seal. Grab the flywheel with both hands and try to fell some play in any direction.

Throttle cables are cheap, I replace them every year or so to keep the smooth throttle action, well worth the $10.

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Going to inspect the flywheel later with a buddy. If it does have bad crank bearings whats the best route from there?

Rebuild the bottom end? If so I've never done split the cases before and not sure I'd have the experience to do it right.

Do you think I'd be fine with letting a friend of mine who has some experience rebuilding bikes do it? Or should I take it to my local shop?

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I have been experiencing similar issues with my 02 rm 250. I have gone through jetting changes already, new piston, all new crank seals and inspected everything. There is no coolant or gear oil loss after 3 to 4 rides. Recently, I went to my local track and had an issue where the bike would bog around 3/8 throttle. I thought it might be lean bog, but since the time I bought it a year ago it has been increasingly hard, to start to the point where I sometimes need starting fluid. The bog was at random. I am unsure whether that is characteristic of lean bog. At the moment I am about to buy a new stator. Electrical is the only thing I can think that could be the problem considering all jetting is in the ballpark and all other possibilities have been inspected or addressed. It could be the same problem with yours.

Edited by 2 stroke forever

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