'02 RM250 jetting again

[Marklx]

I've got the jetting real close on my RM, and looking to get it perfect. As my bike is Canadian, it came with diff. jets than the us models. Based on mag tests, I've got the jetting setup much leaner, but wondering if the slide is the same. In the users manual, my slide is spec'd as cutaway #7.

If anyone out there has a US RM, could you check the manual to see what the stock spec'd slide # is?

Thnx,

Mark

 

[Chief]

Hey Mark,

I have an an 01 250 that came stock with a #7 slide. Eric Gore shaved 1mm off of it. I can tell you it runs a lot smoother now but I also had head mods done at the same time, so I can't say for sure how much effect this mod has. My guess is alone, it would have made a considerable difference.
I'm at appx 1000 ft elevation, temps 30-90 F. It was a better deal than buying a different slide.

Joe Chief

 

[Marklx]

Thanks Chief,

In all my readings about jetting, I haven't found much about the slides interaction with things. As I've tried different combos of jets, needle settings, etc with seemingly no impact on that low end burble, I figured the slide was the next place to look. Just yesterday, I did order two needles, one 1/2 clip change, and one needle that is a bigger o.d. (leaner as well).

What is the throttle position affected by the slide settings? It would seem shaving 1 mm off the slide would have the bike running leaner, but then jetting never seems to make perfect sense to me.

Thanx,

Mark

 

[Vytas]

Chief,
Did yo have any other mods done? I should get my cylinder back this week with head mod and porting from Eric. He said that I will probably have to lean up the jetting and should cut the slide 1mm. Has this mod worked well for you? When was it done? Eric stated that this is summer mod. How does you bike run in cooler weather? What was your final jetting?

2001 RM250
2000 KX65
1999 JR50
1997 CR80

 

[Chief]

Mark & Vytas

Mark,

I know what you mean about the burble. It drove me NUTS!!! I highly recommend trying this: Reduce the tension on your exhaust valve spring. Mine is factory 1/4 turn clockwise, I backed it off to 1/8 and it helped, then I tried zero tension and the burble has dissapeared. Sometimes I am loping around on singletracks, over rocks, on woods trails that are so vague I have to stop just to visually make it out, I almost feel guilty for dogging it so badly, but it runs as smooth as glass at very low rpm, sometimes for close to 45 minutes straight, then it starts to load up a bit, but it's running better than I should hope for under these conditions anyway. Also it still pulls well up top. (Easy adjustment, just loosen the (2) 8mm bolts on the upper left side of the jug and turn the cap to feel aound for zero, then go from there). I've heard of others making this adjustment for different riding conditions. The top of the range should be suffering, but I haven't noticed.

I have the next fatter needle, but the original seems to work fine for me. The 1/2 clip should help with your fine tuning.

Cutting the slide leans out the mixture up to about 1/4 throttle.

I think you'll find the perfect combo, then you'll have a baseline for temp & altitude changes. Feel free to e-mail me w/ your progress.


Vytas,

I sent the whole top end to Eric after I seized it.:ugg: I believe he welded the bridges, (then replated) and widened the squishband. No porting but you should have a world of difference when you get it back.

I got my finished parts back in September (temps appx 60-75), with the slide cut and the exh. spring adj, 48 pilot, clip position down one from top, and 165 main. (maybe the main could be leaned out more, but it ran well anyway)

When the temps dropped to around 30 or lower, I had gradually richened up to a 52 pilot and clip to the center position. I left the main @ 165. I think the leaner slide works well even when it's cold. The only other mod I did was one tooth less on the front sprocket. It's a comprimise that was worth it for most of my conditions. It runs well when it's cold outside.

First time you start it you might want to make sure you back out the idle screw a lot, mine idled so high the first time I had to stall it in gear. (bad break in method) I bet you can't wait to get it back together. Good Luck!!!

Joe Chief

 

[Vytas]

Chief,
Thanks for the info, now I have a decent starting point to begin the jetting process. I think that our geographical locations are pretty close so, hopefully, jetting should be close. You are correct about getting it back together, I just finished ordering the remaining parts that I need (rings, top end gasket etc) to put everything back together. I also am installing a VForce reed system. I am really expecting a tremendous boost in performance. With the weather being unseasonably warm in Illinois I will probably tear up the lawn before I get my 'zuki to the track. Thanks again. Keep it up, on two wheels that is!

 

[Marklx]

Hey Chief,

Thanx for the great info. My needles should arrive today, so the tuning will begin. I'll try the exhaust valve thing, as it is easier than changing jets, but will wait 'til I try the needles first, to keep track of things. And if all else fails, look at the slide option.

One other question for now........what oil are you mixing, and at what ratio? I'm using SuperM @32:1. Get some spooge, but not bad. At the end of a day at the track, maybe 1/2" trickle down the silencer. With stock jets, the epa was after me.

Thanx again,

Mark

 

[Vytas]

Mark,
I am running TORCO race fuel and GP-7 with a 32:1 mix. I have had a liitle bit of spooge depending on how fast or slow I ride with stock jetting. When I took off the top end it was a lot cleaner than I had expected. I think that when I start to ride faster all the time, not constantly idling or running in first waiting for my kids to catch up, that the level of spooge will be even less.

 

[Chief]

Mark,

I'm still experimenting with different fuels/oils. Suzuki cci 32:1 with mobil 93 seemed the worst I tried. (lot of spooge) Golden specto @ 40:1 Sunoco 94 was better (less spooge), Amsoil @ 50:1 w/ Sunoco had no spooge, ran nice. I have some mobil mx2t that I will try next with amoco 93. Maybe 40:1 to start with. I tried cam2 gas but didn't like it.

Maybe a little spooge is good. Keep the pipe from rusting:)


Joe Chief

 

[Marklx]

Chief,

Mobil MX2t will be my next try. The superM is o.k., but I've heard too much good stuff about the mobil, so the next tankful will be mobil. I've got 4 fresh gallons of M mixed, so guess that will be next week.

Also, RM_Guy posted that you have some pic's of the modified slide. I would LOVE to have those. I'm about to do this and could sure use some comparison photos before I fire up the dremel. Also, what kind of bit did you use?

Thanks,

Mark

email to: [email protected]

 

[zorlac_147]

I run Red Line sythetic racing oil mix at 70:1 in my 02 rm 250 (and in every bike I have owned, don't let it scare you it will not blow) and do not have any problems with "spooge" ever. My bike seems to be running very crisp. I am at higher elevation probably than you guys. my jetting for 3500 ft is:
48 pilot
168 main
50 power jet
second clip stock needle

I will be riding it at see level quite a bit this summer so if you guys come to a conclusion let me know. I figured at this point I would only raise the needle a notch and maybe go to a 170 main. Has anyone out there tryed other gearing on the 02 rm 250 to get a little more top speed? Mine has a 49 on the rear now. I'm thinking about dropping to a 47.

 

[Marklx]

Zorlac,

You're right. I am nervous about running that thin a ratio. But the difference in your jetting and mine is only the second clip on the needle. On the third, I have the burble, on the 2nd it is real clean. Too clean and sounds lean, with a little detonation. That's why I've ordered the 1/2 clip richer needle, which should be in today. While I live at sea level, many of the socal tracks are up a couple thousand feet. But I want to get it right at sea level and adjust from there. I'll let you know how the new needle, and possible slide cutting go.

Mark