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Discussion Starter #1
so my cranking compression is too high on my wheeler and causing some slight issues. It is 130 lbs without the throttle open. Without the mechinism in, it is 140 lbs. so its not doing much being its supposed to be 114 with the throttle wide open. The end on the dm is worn .005 were it contacts the valve bucket while cranking. How are you guys fixing the issue? I have read that some people are heating them then bending the arm so it opens the valve more. Is this the only way to fix the problem other than buying a new oem exhaust cam? If so has anyone had succes with bending the the dm. I would like to have it set properly for quick xc starts. It starts good without the throttle pressed but i should be able to add a little throttle if needed without stalling the starter.
 

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Discussion Starter #3
I would prefer to fix mine so i could get the cranking compression right were i want it. But what are you looking get for one?
 

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Discussion Starter #6
Didnt have any issue when my exhaust valves were .008 but now they are opened up to .010 and i installed intake and exhaust hotcams and i cant apply any throttle or it stalls the starter. Starts great with no throttle input. shiftx450 what is your cranking compression?
 

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The lever isn't the issue. You need to check and make sure the dcm is working and not in a bind and make sure you installed the thin washer that goes on it. If that all checks out you have a bad exhaust cam the base circle of the camshaft is off causing the dcm to not engage the exhaust valve bucket far enough to release the cylinders compression. Now you can modify the dcm to fix for the cam being off if its not the fist thing I mentioned.
 

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Discussion Starter #8
Mine moves freely and the washer is installed, it does open the exhaust valve some. When the end of the dm is on top of the valve bucket if i pivot the weight towards the outside of the cam i can see the valve bucket move closed then when i flip it back towards the center were it would be while cranking i can see and feel it open the valve. I pulled mine out and visually saw the wear on the end then confimed it with a micrometer being worn .005 of an inch. The cam is almost brand new but i could put my stock exhaust cam back in and check my cranking compression again to eliminate a cam base circle issue.
 

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You said before you could start the bike with no issues tells me your cam is off ,fairly common on aftermarket cams. Or your lever is worn and you will need to bend it or just run a tighter clearance ( that's what I would do).
 

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Discussion Starter #10
Ya i lost a couple thousand when i installed the cam because my exhaust was at .008" so i set them at .010" when installing the new cam. Used to have the same issue when i first got the wheeler but since the valves had got a little tighter and it went away. I will try bending it tomorrow at work and report back. I should be aiming for around 100-115 psi cranking compression with the throttle wide open correct?
 

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Discussion Starter #12
Ok sounds good thanks for the info. I will post up the results when i get it done.
 

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Discussion Starter #13
so i bent my dm today and got my cranking compression at 100 with wide open throttle. The only problem is i dont think i heated it enough before i bent it because i thought i saw a small hairline crack on top of the bend. I looked under a magnifing glass and it has a very tiny crack in it. I realize the mechinism is only under light pressure while cranking and not doing anything when running but i am guessing it is risky running it like that. Sucks cause i have it set right were i want it but i am slightly concerned.
 

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The above mentioned run tighter clearance sounds like it should've been the better alternative.

You definitely don't want that little arm breaking and getting banged around inside your motor. Definite catastrophic failure there!

Sounds like you may need a new decompression mechanism.
 

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Discussion Starter #18
subscribing to this thread, valuable information in here.
I used that decompression mechanism that cracked after I tig welded it for alot of hours with no failures
 
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