strange starter problem

03 wr 450.I have put a new battery in,04 upgrade .Starts fine when cold and will crank for ever if i forget choke, so i believe starter motor is o.k. Some times when hot it goes to crank o.k the slows like a flat battery.When this happens if i go to kick start it it appears to be locked up.Thats the weird part.It appears like when you try to kick a 426 with out using the decompression lever to go past t.d.c.If i rock the bike or let it sit for a while it eventually comes good.Any ideas would be appreciatted. :thumbsup:

Check the starter clutch (worn, loose bolts), starter windings (bad contact), starter bearings (worn).

This happens occasionally when the motor stops at just the right spot on the compression stroke. The decomp is not engaged at that point and the starter cannot turn the engine without it. Just put the bike in gear and rock it back and forth slightly to get the engine to rotate a little and engage the decomp pin. Then it should start right up. I think it's pretty normal just a slight design flaw. Both of my 450's do this every once in a while.

Be Happy You Have A Starter On Your Bike At All...................:thumbsup:

I have the same problem but not very often, I always thought it had to do with the YZ exhaust cam, looks like thats not the case. I have to give my bike a very hard boot to get the motor to move before the starter will work again. Heavy duty compression!

Thanks for the replys.Ihave put new bearings in the starter so maybe starter is o.k ?.I will pull the starter clutch and check that out.How does the auto deco work and does it work when the motor is running.

The auto decomp is a mechanism in the exhaust cam. There is a pin that sticks out on the side opposite the lobe which opens the left exhaust valve. It is controlled by a centrifigal weight so that it retracts as soon as the engine speed picks up to something a little less than idle. If you've had the starter apart and the brush length is in spec and the bearings good then most likely the starter is ok.

Here's a link to some pics of the cam. It's about how to install it in the older bikes but you already have it. The pics should give you a better idea of how it works.

http://www.thumperfaq.com/autodecomp.htm

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