Need Help

C

CRF250R04

Member

Sep 20, 2009

3

0

• Sep 20, 2009

• #1

Hi everyone im a new user.

I own a CRF250R 04 model i just got a bike shop to put in a new crank i got the motor back all good. I put the top end on the bike and all timing marks are lining up but when i kick the bike over i just get back fire through the exhaust after id say between 10 - 15 kicks.......

Its realy getting to me and i do not no what it could be. does anyone have any idears????? Thanks for the time.

 

whenfoxforks-ruled

Old MX Racer

~SPONSOR~

Oct 19, 2006

8,129

2

Merrillville,Indiana

• Sep 20, 2009

• #2

Recheck the timing and valve clearances. Check the ap circuit for proper timing/function. You could read for days on the same subject via the search on this site. Welcome and have fun!

 

C

CRF250R04

Member

Sep 20, 2009

3

0

• Sep 20, 2009

• Thread starter
• #3

Thank you. Now i have just checked them all again they are all TDC?????

 

IndyMX

Crash Test Dummy

~SPONSOR~

Jul 18, 2006

5,548

2

Amo, IN

• Sep 20, 2009

• #4

Are the intake cam lobes pointing to the back of the bike?

 

C

CRF250R04

Member

Sep 20, 2009

3

0

• Sep 20, 2009

• Thread starter
• #5

Yes they sure are

 

IndyMX

Crash Test Dummy

~SPONSOR~

Jul 18, 2006

5,548

2

Amo, IN

• Sep 20, 2009

• #6

Well.. Not sure how prevalent this is on Honda's.. But my brothers KX250F had the timing gear slip on the cam. Seems the gear is only using an interference fit. No splines or keys.

Had a guy find that problem, and fix it for me. It required him resetting the gear on the cam, then tack welding the whole thing.

I'm afraid that if this is your problem, you'll likely need someone with a lot more talent with engines to diagnose. Might just be time to take the whole thing to the shop.

 

M

Matt90GT

Member

May 3, 2002

1,517

1

• Sep 20, 2009

• #7

Look at the pics on this post:

http://crfsonly.com/forum/viewtopic.php?t=27479&highlight=cam+timing

That is the 450, the only thing different is the cam gear has 2 hash marks that line up with the clylinder head top when it is timed properly.

What is your valve specs?

Also have you cleaned the carb? Pilot, main, AP circuit, 1 way valves in the carb and the bowl and cleaned/greased/adjusted the hotstart???

 

T

T_Bois

Member

Sep 13, 2009

33

0

• Sep 22, 2009

• #8

I'd check the compression. If valve timing is off or the valves are too tight, the compression will be low to nill.