New Parts but won't start cold

I've been searching for answers and it seems like I have covered everything, so maybe you guys can help me out. Here goes.

Bike: '05 CRF 450R

Bike ran fine last year but was very high on hours (no hour meter, and I bought it new). I decided to rebuild the motor. New crank, all new bearings and seals, timing chain, tensioner, guide, JE 13.5:1 piston kit, and new '08 big bore thumpers head with stainless valves. Still has stock exhaust and cam.

Bike is all together and does not kickstart when cold. I can bump start it easily (have put 2.5hrs on it after starting it this way). It runs good, has lots of power, and restarts when its warm. Yesterday I laid it over in a corner and it was a bear to start. Kicked many times and it would fire but not start. Had to bump start it again.

Here is what I have checked out:

Intake valve clearance: .005"

Exhaust valve clearance: .009"

I put the .009 in the exhaust valve, and then the .014 in the decompressor and set it.

I have checked and rechecked the timing according to the flywheel marks.

I even tried it a tooth off and it wouldn't start that way either.

I have the second hash mark on the flywheel lined up and the cam mark and pointer lined up.

I have also cleaned the carb. out thoroughly. 168 main 72 starting jet 42 pilot jet and 1 1/4 turn out on the bottom carb. adjustment screw.

What do you think? What am I missing?

Is your hotstart working properly?

I made sure there was slack in the hot start cable, and blew some air into the hole that it goes in. Thats about it.

Adjust the decompressor to .016" and see what you get.

Ok, thanks. I will try that.

On a side note, ( its hard to explain but...) it just doesn't sound the same when kicking it as it did last year. It just has a thub, thub sound instead of the normal thub thub thub. Almost like when you hold the throttle open and and try to start some bikes.

Its the higher compression piston. If the adjustment doesn't help, or it gets worse, adjust it the other way. Close it up to about .012" and see what that gets you.

If its the same, check out the sticky regarding the timing. You may have it one tooth off.

I did 2 things. Opened up the decompressor to .016" And also found the tiny spring on the decompressor weight was not working as it should. Now it starts. Thanks.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now