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Post by devo344a on Apr 6, 2013 14:39:12 GMT -5
This is the second chain to break have no idea why I installed a scrappydog BBk,A9cam and cant find a reason for it to break everything is the same height the only thing thats different is the head gasket the stock one was a tin one and the new one is thicker like the gasket on a car when i put in the second chain i didnt put the spring back into the tensioner and it was still a little tight but thought it would strech a little oh and its a 49cc with the 100cc BBK anyone have any ideas
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Post by JR on Apr 6, 2013 14:42:35 GMT -5
What is the compression you have now. Can you do a check and postthe results.
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Post by alleyoop on Apr 6, 2013 14:48:42 GMT -5
That is why your breaking your chains, to tight. The chain should have at least 1/4-3/8 play on the top of the chain then the tensioner pushs it down against the guide. You need a chain with at least one more link. when on without the tensioner you should be able to push the top of the chain down with your finger.
Alleyoop
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Post by woowilly on Apr 6, 2013 15:41:58 GMT -5
chains set too loose will snap from the shock load forces.
too tight increases wear rate. and can cause breaking the guides (and tensionizer)
which then makes the chain too loose and then the chain snaps...
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Post by devo344a on Apr 6, 2013 17:04:35 GMT -5
How do you find a chain with an extra link?? I know its tight thats why i didnt put the spring back in the tensioner I could barely push the chain down with a screwdriver can you buy a head gasket out of the tin for a BBK havnt been able to find one yet
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Post by devo344a on Apr 6, 2013 17:24:12 GMT -5
Forgot dont have a way to check compression I broke the first chain after putting the BBK with a stock head on it alot of compression on that one then I put on the bigbore head from scrappy both times the chain was extremly tight
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Post by JR on Apr 6, 2013 17:32:57 GMT -5
Are you putting a gasket under the cylinder?
remove it an put a bead of silicon ther instead, it could squash down and give you a hair more slack, then consider milling the head or cylinder a little if you have clearance for it. Those together might give you a little wiggle space. You are right that chains do stretch that is why they have tensioners and why motorcycles have an adjusting nut to take slack in the chain up.
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Post by alleyoop on Apr 6, 2013 17:34:36 GMT -5
Count the links on the chain that broke should be in the 40s.
Also compare the cam sprocket to the oem cam the A9 Sprocket may be a bigger diameter.
Alleyoop
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Post by devo344a on Apr 6, 2013 17:45:39 GMT -5
I checked the stock cam to the A-9 its the same the jug and the head are both the same height as the stock. I think I found the tin head gasket and I will use silicone like Doug suggested. The head gasket thickness is the only differance from stock and its a good bit I might put the stock head back on with the 100cc BBK and get the compression back up the power loss from putting on the big bore head was alot
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Post by triker on Apr 6, 2013 18:19:23 GMT -5
The chain should have 82 total links. 41 outer and 41 inner. I have looked far and wide for a chain with an extra link, I haven't found one yet. If the chain was to tight with the stock head, the height of the cylinder is to tall, or the cam sprocket is to large of a diameter. I doubt the had gasket is to thick.
Roy
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Post by triker on Apr 6, 2013 18:37:00 GMT -5
I have an A9 cam that I didn't use because the chain was to tight, the cam sprocket measures 66.54mm at the peaks and 60.21mm in the valleys. A stock cam I have measures 66.38mm at the peaks and 59.95mm in the valleys.
Roy
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Post by devo344a on Apr 6, 2013 21:23:12 GMT -5
What I willm do is when i get the new chain I will put the stock cam in and see if it is loose enough then I will know if its the cam or not. How much differance does the A-9 cam make ? And it was tight with both heads so it has to be either the A-9 cam or the head gasket you guys have been alot of help and I wanna thank ya
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Post by devo344a on Apr 8, 2013 11:06:31 GMT -5
Well I mesured the height of the jug,head,and matched up the A-9 cam with the stock ones and the only differance is the head gasket when i get the new head gasket the tin one i will see how much differance there is with them
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Post by wilds on Apr 8, 2013 11:57:44 GMT -5
Just a thought...
Are you sure that the lower chain guide is in the right possition and that it's not turned upside down?
If you do that, the chain might seems too short.
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Post by devo344a on Apr 8, 2013 13:44:55 GMT -5
everything was in place thats why this is so mysterious everything seems right cant wait to get the new chain and the tin head gasket to be able to measure it all
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..BAD TO THE BONE..
