2004 CR250R - Needs Low End for Offroad

BigBoreFan58

Member
Oct 7, 2006
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Can anyone recommend how to get low end out of a 2004 CR250R? My buddy bought one of these brand new for 4K. He likes everything but the motor. He had a 96CR250, and his 04 is no 96 in the motor dept. He rides offroad, GNCC, Hare Scrambles, and is a C rider.

He has a light flywheel on it, 6 or 8 oz Steahly. He has a ProCircuit pipe with the stock muffler. It has a MotoTassanari V-Force Reed cage. Other than that, the motor is stock.

Has anyome tried a head from PhatHead Racing, or the Boyesen exhaust flange?

I heard that ProCircuit has some porting that works. I believe Dave Chase came up with it. I also think Dave now works at White Brothers.

Anyone tried any BigBVore kits?

Any help is appreciated.
 

bll

Member
Aug 24, 2006
20
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did the pc pipe help?

i bought an 02 with a fmf sst pipe on it. when i put the stock pipe back on it the low end got better.
i also have a 13 oz weight and one tooth taller in the rear.
man my girl sure is slow but i am beating all the people i used to beat by more distance and i am having a ton of fun.

i'd like to ride a bike with a real motor to see what i am missing but i sure am digging this old girl. she gets going pretty good when getting up into the powerband. i am an A rider though so maybe that is why i can sacrifice the low end and still get around, hell i don't know, just know that i love this bike.
 

BigBoreFan58

Member
Oct 7, 2006
5
0
bll said:
did the pc pipe help?

i bought an 02 with a fmf sst pipe on it. when i put the stock pipe back on it the low end got better.
i also have a 13 oz weight and one tooth taller in the rear.
man my girl sure is slow but i am beating all the people i used to beat by more distance and i am having a ton of fun.

i'd like to ride a bike with a real motor to see what i am missing but i sure am digging this old girl. she gets going pretty good when getting up into the powerband. i am an A rider though so maybe that is why i can sacrifice the low end and still get around, hell i don't know, just know that i love this bike.

Not sure if the PC pipe helped, he never rode it stock. I would have preferred the FMF Gnarly, it is an off road pipe.
 

motometal

LIFETIME SPONSOR
Sep 3, 2001
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flywheel doesn't actually add any low end power, but I think it's a winner-I went with the heaviest one and like it a lot. Tried the exhaust flange, didn't like it. You could rework the head to raise compression a bit, which would help low end but then you'd have to run race fuel, at least partial mix. Or, get serious about it and have the cylinder ported. Big bore in my opinion is only to fix a damaged cylinder...I wouldn't do it to an otherwise "good" cylinder, at least on a CR. I went up two teeth on the rear sprocket. Oh yeah, last but not least jetting!
 

bll

Member
Aug 24, 2006
20
0
yup, jetting is key. keep the powervalve adjusted too i hear......

now if someone will just answer my other recent post about how to adjust the RC valve i'd be dialed

yea i know flywheel doesn't help low end, i would imagine it hurts it a little bit. i love the heavy weight, some days i feel like i can't stall the bike, other days i stall it plenty.....wierd..same trails

anyway,
i have a two teeth bigger rear sprocket out in the garage i have been meaning to try it.

thx for the feedback on the flange, i wondered about those.
 

mx547

Ortho doc's wet dream
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Nov 24, 2000
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i have an exhaust flange on mine but i also put on an fmf shorty at the same time. it helped a little but since i put them on together, i can't comment on their individual merits. i went with the cometic high compression head gasket too but couldn't tell any difference (i'm running pump 91). i also went up two teeth on the rear which makes a noticeable difference.

as far as jetting goes, the best thing i did was to ditch the crappy mikuni and put on a keihin.
 

motometal

LIFETIME SPONSOR
Sep 3, 2001
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under certain circumstances this can help, advancing will tend to increase low and decrease high/overev. Somewhat the same effect as adding compression. If you are playing with advancing timing you better be running race fuel.
 

blackjack

Member
Aug 11, 2002
55
0
Best engine mods for '02-06 Cr's-

- Fmf/Pro circuit pipe with shorty muffler
- Steahly flywheel
- JD jetting kit
- Tassirini or Boyeson reeds
- MX Bonz 5mm exhaust spacer
- advance timing
- Wisecon piston with .010 Cometic base gasket

Do your suspension - make sure ride height and springs are correct, then revalve for better impact compliance.

I run my '02 in the woods 3rd gear with 14 front and 51 rear sprocket (taller than stock).
 

SQUIRLEYMOFO

Member
Jun 11, 2002
310
0
blackjack said:
Best engine mods for '02-06 Cr's-

- Fmf/Pro circuit pipe with shorty muffler
- Steahly flywheel
- JD jetting kit
- Tassirini or Boyeson reeds
- MX Bonz 5mm exhaust spacer
- advance timing
- Wisecon piston with .010 Cometic base gasket

Do your suspension - make sure ride height and springs are correct, then revalve for better impact compliance.

I run my '02 in the woods 3rd gear with 14 front and 51 rear sprocket (taller than stock).
Sounds good how do I advance the timing please? Also is 101 octane gonna be enough?
 

blackjack

Member
Aug 11, 2002
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SQUIRLEYMOFO said:
Sounds good how do I advance the timing please? Also is 101 octane gonna be enough?

Remove lhs ignition cover and you will locate the ignition pickup at the bottom. There is a small plate at the bottom that you will have to slot to get the whole stator plate to move. Loosen the 3 plate bolts and rotate the whole plate clockwise to advance the timing.
 

blackjack

Member
Aug 11, 2002
55
0
SQUIRLEYMOFO said:
Sounds good how do I advance the timing please? Also is 101 octane gonna be enough?

Remove lhs ignition cover and you will locate the ignition pickup at the bottom. There is a small plate at the bottom that you will have to slot to get the whole stator plate to move. Loosen the 3 plate bolts and rotate the whole plate clockwise to advance the timing.

Pump gas should also be fine here unless you are running higher than stock compression.
 

Josherichy

Member
Sep 23, 2006
125
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put the hevyest flywheel weaight you can fit and for us the Gnarly pipe worked well for bottm end. the jetting is hard for the people that ride behind you.
 

motometal

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Sep 3, 2001
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SQUIRLEYMOFO said:
Sounds good how do I advance the timing please? Also is 101 octane gonna be enough?


You MIGHT get by with pump fuel...in my opinion it's borderline too low octane for a crisply jetted stocker, let alone advancing timing etc. You can't always hear when they ping. I'd run at least 50% race fuel, how much fuel do you go through?
 

SQUIRLEYMOFO

Member
Jun 11, 2002
310
0
motometal said:
You MIGHT get by with pump fuel...in my opinion it's borderline too low octane for a crisply jetted stocker, let alone advancing timing etc. You can't always hear when they ping. I'd run at least 50% race fuel, how much fuel do you go through?
I would gadly buy some race fuel. As I don't use much, but I don't have a source..........is it possible to buy online?
 
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