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Old 12-25-2012, 09:35 AM   #50566
Spud Rider
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Joined: Jun 2008
Location: Idaho
Oddometer: 3,815
Originally Posted by mcma111 View Post

Spring #6 can become a problem when it loses it's tension. My son's bike would not start when cold and I found that the engine would rotate around to TDC with a pressurized cylinder and not be able to get past TDC due to the decom not opening the right exhaust valve. I finally replaced that little spring and the engine would start normally again. I have a buddy's bike that is doing the exact same thing and we will be replacing the spring this coming week.

Thank you for posting the valuable information. That spring makes the decompression cam rotate counterclockwise at engine speeds less than 800 rpm, engaging the right exhaust valve. When the engine is running (with speeds greater than 800 rpm) that spring is compressed by centrifugal force, and the decompression cam rotates clockwise, disengaging from the right exhaust valve. That decompression spring costs less than $2. Therefore, I now plan to replace that spring with a new one every time I remove the camshaft for any reason.

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