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03' yz 250f Big bore jetting

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Hi.. I'm just a lurker that watches and learns from what I see posted.. I dont post much at all..

Anyways I have been looking at jetting specs on yz250f big bores and thought maybe a sticky would keep the repete posts down.. I know every bike is set up different..

So specs/parts/areas might help some guys.. If you would like to start a sticky.. heres my info..

just a thought..

2003 yz 250f

JE 290 kit (off e-bay ATV Unlimited $445.00 shipped 4 days to my door)

Cometic gaskets included

Valve job

Light porting

Stock cams

Stock pipe

14-49 gearing

No carb mod.

Zip ty mixture screw

2000-4500 ft

42 pilot (40 as a 250)

168 main (178 as a 250)

72 (mid ? ) 72 as a 250

Riding type:

expert tight mountain single track / fast desert woops/ very tight rocky trail breakin

(12 hrs/2 rides on 290 kit no problems, no sealer on head gasket)

Runs great. starts easy, no burps, great low end, nice top. Not a 450 but makes me happy. Much easyer on the clutch. 1-2 gears up every where..

I over heated before the big bore and I still over heat rock picking at walking speed.. tried 1.1 cap to 1.8..

Going to big radiators this week.

AutoPwr YAMAHA YZF 250 YZ 250F 01-05 Aluminum Radiator off e-bay.. $145.00 shipped (will update on this)

If this doesn't help I'm going to make a catch tank or a bigger Camel back ! haha

Thanks.. Butch

Edited by nikad58

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Went to 172 main

72 mid ?

45 pilot.

Runs perfect, starts easy and great color on plug..

It really has so much power over the 250 its amazing ! I need more gears !

AutoPwr YAMAHA YZF 250 YZ 250F 01-05 Aluminum Radiator (from e-bay)

I used to over heat after long hills and picking through rocks..

For $125.00 these radiators are the bomb.. Havnt over heated once.. Look great and I have ran about 15 gallons through the bike..


Forwardpowersports.. Yamaha YZ250F 250F WR250 Complete Clutch Kit - NEW (E-bay $45.00 shipped)

Over heats very fast, starts draging and will leave you with no clutch at all.

Total junk and a waste of money..

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Just throwing out a 6 month up date..

Still runs very strong.. Everyone that rides it falls in love with the motor..

The radiators have held up great even after a few hard crashes..

I cant even guess on the hours I have on it now but it's alot..50-60 gallons ?

Best money I have ever put into a bike.. okok I already have the suspension done..

The only thing I have noticed now is it needs the hot start used most of the time when hot to get it started again but ALWAYS starts..

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