03 rm250 jetting help

[chrismxer]

Eric or anybody,

My 03 rm 250 has very poor responce right off the bottom. It seems like I'm alway's stalling it. I know it's a known problem with that year and have tried different jetting, wet sanded my slide from a 6.5 to a 7.0, retarded the timing, fly wheel weight and everything else I can think of. Is porting my awnser or is there something else I could try? I use it for woods riding and would like it to have more of a typical woods type power band.

Also my Idle changes through out my ride. Sometimes it wants to Idle good other times after I let off the gas and hold the clutch in I have to keep revving it so it doesn't die. I don't think it's my clutch.

Thanks, Chris.

 

[snb73]

Chris,

What is your current jetting, altitude, plug, pipe and fuel? I had a similar problem with my 03; stock jetting and 93 pump fuel, the bike came with and FMF Fatty pipe. I had almost no response from off-idle to 1/8 throttle, then it would take off from 1/8 to 1/4 throttle. Very unpredictable.

I am in southern MD at sea level to 1000 ft above, with varying humidity. I rejetted and installed Boysen rad valve, switched to "Sunoco Standard Leaded race fuel", and the problem was solved. I have heard people say jetting w/ race fuel is kinda like cheating, but it works for me.

Good luck, Steve.

Stock was;

main #175
Needle #N8RH 3rd clip
Slow #48
Air screw 1 1/2 turns
slide #6.5
Power Jet #50

My jetting:

Sunoco 110 (purple) 40:1 w/ golden spectro synthetic
FMF Fatty Pipe
NGK BR8EG
168 Main
48 power jet
45 slow jet
needle 2nd clip (1 lean from center)
Air Screw 1 1/4 - 1 3/4 (depending on conditions)

Here is some good reading;

http://ericgorr.com/techarticles/carbtuning.html

http://www.dirtrider.net/forums3/showthread.php?t=42618

http://www.thumperfaq.com/mxa_jetting.htm


Here are a few sites to give you a baseline;

http://www.fmfracing.com/jetting_2002.asp

http://www.onthepiperacing.com/foru...262287028eaf11e

http://www.mx-stuff.com/jettingspecs.htm

Fuel charts;

http://www.racegas.com/fuelspecs/default.asp

http://www.vpracingfuels.com/vp_spreadsheet.gif

http://www.vpracingfuels.com/vp_01_...135CCC80#leaded

 

[chrismxer]

Thanks for the very informative responce Steve!! I will read up on that stuff and keep tryin. Also I took my carb off my yz250 and it has a 7.0 slide I might try too.

Right now I have these settings.

165 Main
One size bigger needle on strait portion (leaner) in the # 3 position.
48 slow
air screw at 1.25 - 2. depending.
Power jet is stock (50).
NGK BR8EV

I have a stock pipe and an SST FMF pipe with V-force reed block. Brand new top end and a replated cylinder. Also I run my bike from 100 to 4000', but mostly between 1500 and 3500. I might try a little octane booster but I use a lot of gas in the Mountains and am not going to jet with race gas, too exspensive. I will pull the carb off and do a good cleaning/inspection as Eric explains on that link and what else ever I can find on all those links you provided. Thanks agian.

Chris.

 

[snb73]

Chris,

What part of California are you from? I used to live in Rancho Chuchamunga, Lake Elsinor and Oceanside. I wouldn't suggest buying race fuel from a motorcycle shop, they are too expensive. Around here we pay $60 for a 5 gal jug of VP U-4 or $40 for a 5 gal jug of C-12.

If you are near Pamona or one of the other tracks, they should sell the stuff by the gallon at a reasonable price. I live near Maryland International Raceway/Budds Creek. They sell about six different types of fuel. The one I use is about $5.25 a gallon. When 93 pump gas is $3.55 plus, race fuel isn't that much more. Everyone I talked to said I'd notice a difference, but I was skeptical. Now I don't want to ride on pump gas, lol.

Good luck, let us know how you make out.

Steve

 

[chrismxer]

I live near Sacramento / Bay Area and I can get some race gas for about 5 to 6 bucks a gallon but is twice as much as 92 octane. After you said you use race gas and it cleaned it up I remembered when I first got this bike I would talk to Rodney Smith when I would see him at the tracks and he did the same thing to clean his up too. My track bike is a 06 YZ2250 and runs incredible off pump gas, so I know there is hope. Both of these bikes have very simular cylinders and power valve mechinisms. This was the first year Suzuki ran this engine I think so I was hoping Eric would have some insight on the known problems or fixes?? I might try a 50/50 mix next time I ride this thing.

I am running my stock pipe now because I read on another forum that the SST pipe increases piston crown temps. Any truth to that anybody??

Another thing in Eric Gorrs carb info link he said that advancing the timing helps out with the low end. I thought it was retarding that helped out with the low??

I'll let you know what progress I make.

Thanks, Chris.