snb73

Member
Nov 30, 2003
770
0
Need some input, 2003 RM250 Jetting suggestions?

I just purchased an almost new 2003 RM-250. The bike has probably less than 5 hours on it, its in immaculate condition. The only mod is an FMF Fatty pipe/shorty silencer.

On the test ride, the bike left some spoog residue on the fender, but it felt strong. Once I got home I checked the plug, it was a NGK BCPR5EY. I changed to a BR8EG, drained the fuel, and mixed a fresh batch. I still got some residue on the fender.

After reading the article from Rich about plug reading, I decided to cut the plug. The carbon ring is all the way
up the insulator, with only 2-4mm's at the tip golden. I think its safe to say the jetting is rich?

What would be a good baseline to start from?

Current Jetting;
Main Jet #175
Needle N8RH-3rd
Slow Jet #48
Air Screw 1 1/2
Power Jet #50

Fuel: Sunoco 93 octane(pump super) @ 40:1 w/ Golden Spectro semi sythetic.

Altitude: 200-500 feet above sea level.

Type of riding: Mostly MX, I am about an average yet aggresive rider.

Thanks, Steve.
 
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02'Cr Rider

~SPONSOR~
Nov 20, 2001
216
0
Maybe this can help....I have an 03 rm 250 and basically stop jetting the bike,because i could never get it right...

My current jetting is:
With pro circuit pipe/w spark arrestor and rad valve
also run the same combo with the bills pipe.

162 main
45 pilot summer time/ 48 pilot winter
stock needle @2nd.
A.S. -1 1/2 turns out
48 power jet
7.0 slide
I run this jetting from sea level to 4000' do to trail riding
Running 50/50 race/pump fuel @32:1 MX2T.I only get a little spooge,but the plug is a light tan color with the carbon ring at the base of the insulator.I have gone far as a 158 main jet but ran into heating problems..Hope this helps..
 

Rotaholic

Member
Mar 10, 2004
70
0
I run stock exhaust but boysen pro reeds. Im running a 165 and a 45 and on the second clip. I find this jetting great. I use 98 octane pump gas and motul 800 at 32:1
 

bclapham

LIFETIME SPONSOR
Nov 5, 2001
4,340
0
you really need to swap to a "8" heat range plug- the BR9EG is too cool for a 250, i bet even RC doesnt run a 9!!!!

as for oil, i have heard quite some anechdobtal evidence that Golden Spectro premix oil burns very poorly (ie spooge).

My advice would be go to the shop and get a couple of new plugs (BR8EG), clean the filter, and mix up some fresh gas with Maxima SuperM, Yamalube or another higher quality oil at 32:1.

see how it runs and then start changing jets- usually pilot, needle and then main in that order. dont change the fuel, oil or ratio at that point since it will mess things up.

good luck.
 

snb73

Member
Nov 30, 2003
770
0
bclapham,

I had a brain fart. I do have a BR8EG in my 250. I just ordered some parts for my son's 125 and had the BR9EG on my mind.

Thnks, Steve.
 

snb73

Member
Nov 30, 2003
770
0
I found an online site that sells jets for $9 each. Does anyone know where to purchase jets for less?

Thanks, Steve.
 

Micahdawg

Member
Feb 2, 2001
503
0
Just to throw another combo into the mix. I just got a 2001 RM250 with the following:

BR9EG
162 Main
52 Pilot
Needle at 3rd
air screw .5 out

Klotz @ 32:1 on 93 octane and 500ft.

The past two days I went riding and the rear fender was handsomely covered with spooge. Carb had other issues with blocked lines (mud) so I removed the carb to clean it out.

Anyway, I don't really know what to do in order to clean the burn, but I just ordered a manual to find out what stock was and go from there.

BTW....is that other long skinny jet the Power jet? I don't even know what that was or how to remove it. Are these jets found on newer carbs? Any help would be great.

Oh and the plug was golden tan around the top, but didn't peer down inside to see what it looked like.

Micah
 

_j0kA_

Member
Jan 29, 2002
378
0
ive got a 2004 rm250 with track racing/riding hours on it, runs like a champ with 92 pump and yamalube 2-r @ 32:1

specs for toronto on canada (i think im at sea level)

165 main (stock is 178 i think)
needle 2nd from the top (stock is 4 from the top)
pilot 48 (stock is 50)
air screw - change itall the time but usually around 1.5 turns out

try experimenting with different settings and i highly suggest yamalube 2-r.. great racing fluid with a very clean burn
 

2-Strokes 4-ever

~SPONSOR~
Feb 9, 2005
1,842
4
Missouri
Remember that your fuel/oil ratio can have an effect on your overall jetting too. 32:1 will be a leaner mix than 50:1. Sounds wierd, but less oil means the ratio of fuel entering the carb. is more, therefor richer (fuel-wise). Before messing with jets, find an oil type, fuel type, and ratio you will be consistent with.
I had cylinder work done to my '03 for woods riding. The company (Varner Motorsports) let me know that jetting the '03 is tricky. They also said that if I insist on running an aftermarket pipe, I MUST run 50/50 race gas. (Gnarly pipe adds compression).
Here's what I have found to work: altitude 500-1000 ft. above sea level, mix at 48:1 (synthetic oil)with 92 octane and 1oz. per gallon of octane booster, stock pipe/FMF Q muffler, V-Force reeds, 7.0 carb. slide...(leaner than stock 6.5)
COLD below 40f....airscrew 1 1/4...pilot 48...needle ALWAYS STOCK...main 172
40f.-70f....airscrew 1 1/2...pilot 45............main 170
above 70f....airscrew 1 3/4-2...pilot 45........main 168
In some cases, at the extreme end of the temperature scale, I still do get light spooge on rear fender...but I'm more comfortable with that, than seizing her up.
 

Micahdawg

Member
Feb 2, 2001
503
0
Before this turns into a leaner/richer argument..... let me follow up the last post with this:

There is a difference between rich/lean PREMIX RATIO and
rich/lean AIR/FUEL ratio. Just so people don't jump in and nit pick the topic.

Also, I assume that bigger number jets flow more fuel right? I feel like a tool for asking, but just checking those stock specs up above made me wonder. These bikes must be really fat from the factory.

Micah
 

d36RM racer

Member
May 26, 2004
123
0
I have a sst pipe and rad valve on my 03 and i run a 170 main and a 45 pilot on vp 110 race gas i can run pump gas but it pings when its under a big load going up a big hill or riding hard on the track
 
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