06 CRF250R randomly shut down on me

Video 

 

 http://www.youtube.com/watch?v=0wDB5MuHfCw

 

 

Bike would not restart after this

 

1. has spark

2. is getting fuel

3. intake valves were tight, left side tighter than right - reshimmed to .005

4. Bike still would not start. 

 

We pulled head and performed leak test on valves, left side leaked, right side sealed. Also found chain tensioner spring tab to be broken

 

left side valve has noticeable carbon build up, right side is clean

 

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thoughts? 

 

 

 

rebuild the head with new valves and seals.

Can you run SS valves with copper seats? 

rebuilt the head with new valves (ss), seals, springs and new head gasket. 

 

reassembled everything, valves are in spec intake =.006 exhaust is .011

 

Bike still will not start.

 

Cleaned carb and three jets, plug is wet and has spark. 

 

Bike still will not start, not even a pop or fire. 

 

any ideas? 

Well I think I got it figured out now, see the grey between the stator pickup wires.. That's tiny metal shavings.. Build up which I'm guessing is causing my issue.

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Waiting on gaskets now

Cleaned everything up, new gasket on stator cover.. Reassembled.. Will not start.. 1 backfire after a bunch of Kicks and throttle swtists.

Has compression

Has nice blue spark on every kick

Plug is wet after kicks

... Carb and jets are clean.. However choke will not stay open now if I give it a throttle twist.

Any ideas? I'm friggen stumped.

Edited by lucrestyle

Maybe the timing chain jumped a tooth?

Maybe the timing chain jumped a tooth?

I rechecked the timing, not just looked... I took head apart and reassembled again, everything is spot on.

Also verified accelator pump is working,

Re checked spark.. Has nice blue spark every kick.

Stumped.

How did you verify the timing?

How did you verify the timing?

Took off cam.. Reinstalled, realigned primary gear to top dead centre on arrow, aligned cam sprocket marks which are in align with head. Cam loabs are facing rearwards.

I rebuilt this engine including new crank, piston, rings and all gaskets and seals 10 hrs ago. Has run flawless since.

That's not the most accurate way to time the cam to the crank, you should use the left-side flywheel plug/window to check the marks on the crank to verify & validate the crank is absolutely at TDC, then check the cam alignment to the head. Try it, don't cost nuthin'.

Edited by Eddie8v

That's not the most accurate way to time the cam to the crank, you should use the flywheel plug windo to check the marks on the crank to verify & validate TDC, then check the cam alignment to the head. Try it, don't cost nuthin'.

Will do, it ran great before.. Are you thinking the flywheel key moved and allowed flywheel to turn 180?

Thanks for the help

I thought you rebuilt the head, installed it, and it wouldn't start. What does it matter how it ran before all that? You could be off one tooth on the chain.

And stop worrying about your flywheel key, for now. We need data. And I assume you properly keyed and installed the flywheel to the proper torque. If you installed your flywheel off-time you could damage something just by kickstarting it.

Edited by Eddie8v

I thought you rebuilt the head, installed it, and it wouldn't start. What does it matter how it ran before all that? You could be off one tooth on the chain.And stop worrying about your flywheel key, for now. We need data. And I assume you properly keyed and installed the flywheel to the proper torque. If you installed your flywheel odd-time you could damage something just by kickstarting it.

Checked the flywheel marks and they didn't line up with the notch on the window.

The flywheel had rotated, I pulled it off to find a sheared woodruff key.

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I'm 100% sure this is the problem, thanks for all the help and remember to check the flywheel timing if you ever experience a random shut down or similar.

had a great ride on Saturday.. put about 3hrs on bike.. ran flawless! 

had a great ride on Saturday.. put about 3hrs on bike.. ran flawless!

damnit ! I started reading at the top and thought all long " I bet something's up with that woodruff key". Came to almost the bottom and went to type it but I seen you found it already! Well atleast you figured out the problem!

You now need to be asking yourself why the key sheared off. I would say most likely you didn't properly torque the flywheel nut.

yeah i wanted to finish this topic in case anyone else comes across it in the future, it may be a good one to add to the FAQ. 

 

In regards to the torque specs, when i rebuilt the engine I did everything to spec, I did not add any thread locker to the threads. I don't think it calls for it, however when i re-installed i added a little blue. Should give me a little insurance. 

 

to sum things up.. if you CRF won't start.. you have an issue.. start at the top (valves) and work your way down.. you will find the problem. My bike starts 1-3rd kick EVERY TIME NOW just as it did before. 

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