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Jetting problems, 03 RM250.

Joined
Aug 8, 2007
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#1
Hi,
I have an 03 RM250 that was jetted horrible when I got it.
I live in West Virginia at about 1200ft. Temps are 80F'
Jetting when purchased.
-45 Pilot,
-170 Main
-stock needle middle clip
-Air screw 2 turns out

This didn't work to well on bottom end. Loaded up really bad. Top end was good, once it cleaned out.

Got a 168 main, great full throttle, black spooge all over rear fender though.

So tried top clip on needle, same. Little better bottom, still blubber.

Tried 42 pilot, same. Little better bottom, still blubber.

Got a 40 pilot, and a n3wk needle at the same time.
N3WK (stock 01 RM250) still rich on bottom, middle clip. Ran worse on bottom, foul, lots of spooge.

Air screw at 2-3 turns, still blubber up to 1/2 throttle, then its great.

Going to try 1st clip tommorow.

Is a N3WK needle leaner than a N8RH?
I went with Bill's pipes recomandation. Top end is great, but below 1/2 thottle is blubbery, not crisp.

It sound like it should be really lean, but it's very rich on bottom. Probaly could go back to 170 main, but I will get bottom end jetted right first.

I would like some jetting help here, please.

Aaron
 
Joined
Jun 21, 2007
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#2
Wow, unless thats a different carb, isn't that a super small pilot? Isn't stock a 58?
Yo must have another issue.
I have a 96 RM250, I have jetting issues as well, different though, my bike runs awesome everywhere, but is fouling plugs every hour. Even after a jetting change.
I am lost.
 
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#3
no, it think stock is a 48 or somewhere around there.

It runs really good, just not if you hold it around 1/4 throttle. It still pulls good on bottom, just not crisp & clean.

I know a 40 pilot seams really lean, but it's no where lean. I just checked the floats, cleaned the carb out, and moved the clip to 1st position o N3WK needle.


Does anybody know if a N3WK is a leaner than a N8RH?
Bill's pipe recommands using a N3WK needle?

It also has a pro circuit pipe, which I hear is the hardest pipe to jet right?
 
Joined
Jun 21, 2007
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#4
Yes, you are right, I was off with the 58 pilot.
My bad.
Good luck trying to find a solution.
 
Joined
Feb 9, 2005
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#5
According to your jetting specs, I would say it may be running a LITTLE rich........but not to the point of blubber. In 90 degree heat at aprox your altitude, I run:
40 pilot
needle 2'nd clip (are you counting the top as #1?)
170 main
A 7.0 slide leans things out across the board too.

Clean air filter?...Nothing obstructing air boot?...Good plug?...Good packing in silencer?
 
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#6
Yeah, I don't know if I'd call it blubber, but it's not crisp on bottom. You could tell it is defentily rich on bottom. Not loading up to bad but, not where I'd like it to be.

Yes top clip as #1. I might have to try a 7.0 slide.

Yes, good packing, good filter, just cleaned air filter and am trying NO-TOIL.


Any possiblity it could be a right crankcase seal in the engine? letting a little oil in the cylinder?
 
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#7
The 03's seem (at least mine) to have a dead spot right off idle........then, hold on! For me, this was a bad combo for woods riding (I marked up a lotta trees). If you're talking about the roll-on low end being kind of non existent, that was something I could never solve with jetting. Porting did the trick in a big way. Ultra fast 250 that needs the delivery massaged a bit. I've owned all the Japanese brands, and in my opinion nothing handles as sweet as a Zook.
 
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Nov 30, 2003
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#8
I live in Southern MD, at about 500 feet ASL. I used 93 octane @40:1 with Mobile Racing 2T:

Plug = BR8ES
Main Jet = 168
Slow Jet = 45
Power Jet = 48
Needle = N8RH @ 3rd Clip
Slide = 6.5

I had the same problem you described, from idle to 1/8 throttle the power was predictable but between 1/8-1/4 throttle the power would switch on. Changing the Power Jet from a 50 to the 48 solved most of this. I started using SUNOCO 110 (CAM2 Purple) this made the jetting much easier and alomost completely emliminated my jetting issues.

Good luck, Steve.



P.S.

Since Mo-Better porting and boring to a 265;

Fuel = Sunoco 110 @40:1 Mobile Racing 2T
Plug = BR8ES
Main Jet = 162
Slow Jet = 42
Power Jet = 48
Needle = N8RH @ 4th Clip
Slide = 6.5

The Main Jet is very sensitive to air temp now. 168-165 above 70-75* F, and 170-172 below 65* F.

Keep in mind this jetting fits me, it may not work for other riding styles.
 
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Jan 22, 2006
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#9
Was following your thread as an observer.. Curious about SNB73's experience and others - does the Mo-Betta porting and 265 overbore normally require significantly leaner jetting?

On my 01 RM265 I had to go from a 48 (stock) to a 40 on the Pilot Circuit and from a 162 (stock) to a 150 on the main to get it to run right. I'm happy with the power now, and I suppose that is all that matters. It just seems like a MAJOR correction to go 3 or 4 sizes smaller than stock.

Anyone have opinions on this?
 
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Feb 2, 2001
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#11
Yota, what kind of fuel are you running? Are you sure the blubber down low isn't pinging? I also don't see anything that bad about your jetting combo and wonder if it's not another issue. I would get ahold of some VP C12 or Sunoco 110 and see if that helps.

Also, clean that carb, check those reeds, make sure your power valves actuate freely, check throttle cable, etc...

For the record I've got a 48 pilot, as 1.5 out, 162 main (165 for cold weather), clip is 2nd from top and bike runs fine except for a little bit of hesitation in the midrange. I think my clip needs moved up to the top. Gas was 108, but now 104. Compression is 240!
 
Joined
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#13
Yota,try starting on bottom,not top first. Change one thing at a time. I hate being the one to bring it up,but your carb is a little more complex than you know! It has a solenoid and a power jet! SNB,you modify a 250 and still run the es plug,that is what I was thinking! RPM,how did you link to someones reply,and who was that? And yes the 134 I messed with went down on the pilot jetting and the top was about perfect on stock jetting.
 
Joined
Dec 19, 2005
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#14
Yota- Our you sure it's a N3WK needle? I know of N3EW, N3CW,N8RW,N3CK and N3EK but not N3WK.
 
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Jul 31, 2002
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#15
Try to borrow a #7 slide to try or grind your own. I've chased many a needle/pilot combo but just couldn't get them to clean up if the slide is wrong. When you get to a #40 pilot with no improvement, something else is off. Either the slide or needle straight section.
 
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