2010 yz450f turbo wont start

Swagger

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Jan 28, 2019
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Hey guys, need some help pinpointing the problem on my 2010 yz450f.
so it's a turbo snowbike setup, and late this past spring I was doing some last runs before season ends, outside temps were warmer, my temp gauge wasnt working and it was overheating on the hillclimbs. Started dying on a hillclimb and loosing power, I thought it was low fuel so I pop a u turn and go down, check to find out it's got plenty of fuel. Tried to start it- no luck. Tow start- no luck. Got towed back the the truck. The turbo setup was used, previously installed on another 2010 yz450f, and I didn't tune it after install. (Dont ask why 🤦‍♂️)
Next season is almost here so I decided it was time to fix it. Procrastination at its finest 😂😂.
So it has a good spark. No amount of starting fluid got it to even pop. Compression check- doesn't feel low on compression at all. Bought a new Leak down tester- 9% leak.

While checking out all the cams and timing, I noticed an inconsistency with true piston TDC and the timing mark on stator. The actual piston/true TDC is about 0.8inches before the TDC mark on stator lines up with mark on the cover. Is that normal, or did I bend my crank?

Heres a video I took to show the situation:

Thanks in advance.
 

Swagger

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I have called around a few local shops and did some research, the flywheel TDC marks are supposed to align with true piston TDC. Everything points to a messed up crank. But is it even possible to somehow warp the crank? arent they a solid one piece forged crank?

I did run a timing light on it to make sure ignition timing was in check with CPS, all checks out, light strobes right over the ignition timing mark. The ignition timing mark in relation to piston is at exact TDC- measured with a rod through spark plug hole- so spark fires at exactly when piston is at true TDC. I know the spark is supposed to be advanced, and should fire before TDC- again pointing towards a messed up crank. Or is that how its supposed to be when kickstarting? does the timing auto advance when it is running under load/ high RPM?
If it is supposed to be advanced even when kickstarting, would this amount of retardation in timing make it impossible to kick start?
 
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Kinda hard to see in your vid but have you checked the valve clearance and the valve timing. it almost looks like you skipped a tooth on the timing chain but its hard to see.
 

Swagger

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Kinda hard to see in your vid but have you checked the valve clearance and the valve timing. it almost looks like you skipped a tooth on the timing chain but its hard to see.
Yup I have checked and double checked valve timing and clearances. Leak down test shows 9% leak.
 

Swagger

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Wow. Yeah Id say a bent rod? Been awhile since ive been into a thumper(and only hondas) But shouldnt you have a fire mark along with tdc mark on the flywheel?
bent rod wouldnt explain the mismatch between TDC mark on flywheel and True piston TDC tho, right?
and yes it has an ignition timing mark, see post #2:

"I did run a timing light on it to make sure ignition timing was in check with CPS, all checks out, light strobes right over the ignition timing mark. The ignition timing mark in relation to piston is at exact TDC- measured with a rod through spark plug hole- so spark fires at exactly when piston is at true TDC. I know the spark is supposed to be advanced, and should fire before TDC- again pointing towards a messed up crank. Or is that how its supposed to be when kickstarting? does the timing auto advance when it is running under load/ high RPM?
If it is supposed to be advanced even when kickstarting, would this amount of retardation in timing make it impossible to kick start?"
 

Swagger

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Maybe im thinking of it wrong but I would think a bent rod could show tdc when the fly wheel isnt at the tdc mark. But you would also lose quite a bit of compression I would think.
bent rod would only affect BDC and TDC piston position within the cylinder.
 
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