2002 RM250 suggestions

[texmx_brian]

Eric, you've helped me alot in performance tuning, modifications, and maintenance on my Honda's in the past. I am selling my beloved bigbore '98 CR125 and getting a 2002 RM250 next week. I race motocross (VET B class) and would fair better on a bigger bike in this Open class.
Your performance tips on my '98 CR125 were HUGE! Airboot and 38mm carb had AMAZING performance increases! I've searched for tips on the 2002 RM250 and have found nothing other than the suggestion to run >100 octane fuel, even in stock form. What are my best mods if any? Coming from a fully modified 125 (144) the high reving 02 RM 250 should fit my style. I am interested in your suggestions on the following:

Recommended Cometic base gasket thickness?
Recommended Carb jetting? (90 F @ 300' AMSL)?
Other air box, air boot mods?
Recommended port timing & head mods?

 

[EricGorr]

The 02RM250 is a great bike, but it has some things that need to be adjusted for better performance.
1) Tighten up the squish clearance by turning down the head. The amount varies based on your needs and available fuel quality. The squish clearance range is from 1-1.5mm
2) Fine tune the jetting which may include a leaner slide and minor adjustments of the needle clip and as many as 4 different slow and main jet sizes to handle the changes in air density by the weather.
3) Grind smooth the transition of the two exhaust valve surfaces, when the valve is in the wide open position. You can get a cheap grinding stone from a hardware store, with a 1/4 diameter shaft and use a hand drill to drive it.

If anybody else has more suggestions especially on aftermarket accessories like a pipe or intake system, please post you opinions and experiences.

Eric

 

[texmx_brian]

Thanks, Eric.
When I get the bike, I'll send you the head and I'll get a chance to look at the exhaust valves so I get a better idea of what you are talking about. I am not familiar with Suzuki's exhaust power valves, yet.
Thanks.

 

[los36]

Pro circuit pipe and shorty silencer! Big gains in the middle and top.
What tracks do you race at brian?

 

[texmx_brian]

I've always seemed to get the best results from ProCircuit pipes, thanks for the suggestion. If / when I dent up the stocker I'll go for the PC pipe & silencer.

Tracks? 3Palms Extreme, SanJacinto MX, Cycle Ranch MX, Village Creek MX & I actually went up to Millville, MN last weekend and raced their big RacerX Vet Race. That is when I decided I have to get a 250 after being on the line with 42 other riders and getting smoked down that long start straight. I hope the 02RM250 does the trick.

 

[los36]

Cool! I'm here in Houston and hit San Jac and Cycle Ranch most often. It's nice to know that I won't be the only yellow 250 (that's not 8 years old) around here! I walso like to go to Swan when they have a big race. There are lots of fast guys on RM's up there.
Eric is 100% right about the jetting. I raced last in March and my bike was running awesome. I broke my ankle and was out for 3 months. I rode a couple of times in June and it ran pretty bad. It was the temperature and humidity. It made a BIG difference.
I have not done the head mod, but I did notice the exhaust valve thing when I did my top-end last month. I will probably smooth it out next time.
As far as the suspension, it needs a little work. Stock, it bottoms everywhere and if you turn in the clickers, it get harsh, quick. I weigh about 170 and J/M Racing was able to revalve it with the stock springs. Any heavier will need new springs, though. It's night and day better with the revalve. Good luck and see you at the races!!

 

[kbob]

Take your intake off and smooth the rubber boot to match the aluminum part. My bike had alot of excess rubber in there from when suzuki molded the rubber boot and they did not match. this will accelerate your fuel and give you a little harder hit.

 

[texmx_brian]

Look forward to seeing you at the track! I am going to try to make it to Cycle Ranch next weekend for the final round of the SoBe Series.

Originally posted by los36
...I did notice the exhaust valve thing when I did my top-end last month. I will probably smooth it out next time.

Help me out here. Call me stupid, but explain what needs to be grinded down on the exhaust. Is it the power vavle that protrudes into the cylinder too far and can catch the piston ring or what? I haven't torn down the cylinder yet, so I am unsure what Suzuki's set up looks like.
Thanks!

 

[los36]

Suzuki uses a 3 piece power valve. 1 main sliding valve(slides up and away from the piston) and 2 rotating sub-exhaust valves. When the main valve is in the full open position , it does not match up very well with the cylinder(on the side farthest from the piston). To reduce turbulence, it would help to grind smooth the junction between the valve and cylinder so that there is a smooth passage for the exhaust gasses to flow through.

texmx_brian:
Don't think I'll make it to Cycle Ranch, I was at Swan last weekend and have to save some cash. Maybe I'll go to San Jac if it's dry enough. See you around!

 

[texmx_brian]

Thanks for explaining the exhaust valve mod.