03 Rappy wont turn over. Decompression pin? - Yamaha Raptor Forum
 
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post #1 of 5 (permalink) Old 08-18-2018, 01:34 PM Thread Starter
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03 Rappy wont turn over. Decompression pin?

Hi all, been lurking for a few years and only posted a few times.
Recently I picked up an 03 660 that suppesdly has a stage 2 hot cam, port&polish, kibble white springs etc. It didn't have a battery but the previous owner said it fired right up.... So i buy it, put a new battery in and the starter tries to engage but seems like it doesn't have the torque to roll the motor over. I pulled the plug and it cranks just fine and I hear the puffing of the piston strokes. Am I wrong in assuming there may be an issue with the decomp pin? Is there a way to precisely check that without pulling the head?
Any help is appreciated

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post #2 of 5 (permalink) Old 08-20-2018, 05:50 PM
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You need to pull the head cover to reach the decomp, not the head.

First, make sure the battery cables are not corroded internally... measure voltage at all connection points WHILE trying to start - do you find any large voltage drops? If so this can point to a possible bad cable or connection.

2nd, check valve clearance - too wide and the decomp is rendered ineffective.

If you do pull the head cover also check cam timing - one tooth off in cam timing can sometimes lead to extra compression/starting issues.

'01 660 Raptor, Burgard +2+1 arms, YFZ Shocks, LSR anti-vibe, CTR pipe, jetted, K&N
'01 Polaris Scrambler 400, K&N
'02 Honda 400ex, Big Gun pipe, jetted, K&N, Lonestar +2 A-arms, Lonestar anti-vibe
'04 Suzuki LTZ400
'16 RZR XP4 1000 Turbo

Last edited by QuadManiac; 08-20-2018 at 06:05 PM.
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post #3 of 5 (permalink) Old 08-21-2018, 04:13 PM
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Make sure to pull the nut and spring off the tensioner BEFORE pulling the valve cover....and install spring and nut AFTER tightening down the cover
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post #4 of 5 (permalink) Old 08-21-2018, 11:29 PM Thread Starter
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So I pulled the valve cover, yes pulled the tensioner first. I found that the previous owner or whomever installed the cam, had the cam gear and rod inside the cam that actuates the decompression pin, off by 180 degrees. The pin wouldn't move up and down at all. I repositioned everything and now it actuates correctly.
Now, as I'm reinstalling the cam I'm finding that at TDC on the crank the cam timing marks are about a half tooth off. I tried moving the chain one tooth either way but to no avail. Is the chain one tooth off on the crank or would that even matter? Or is it just stretched enough to throw it off?

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post #5 of 5 (permalink) Old 08-21-2018, 11:51 PM
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Did you remove the spring from the tensioner first and then look to see how far extended the tensioner is? This tells you whether the chain is near max allowable stretch or not.

'01 660 Raptor, Burgard +2+1 arms, YFZ Shocks, LSR anti-vibe, CTR pipe, jetted, K&N
'01 Polaris Scrambler 400, K&N
'02 Honda 400ex, Big Gun pipe, jetted, K&N, Lonestar +2 A-arms, Lonestar anti-vibe
'04 Suzuki LTZ400
'16 RZR XP4 1000 Turbo
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