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Discussion Starter · #1 ·
I bought a 02 660 raptor and did a compression test and it was a 70psi so I got a new jug, piston, rings, gaskets, and valve springs and it went to 120 psi. what other causes could be the case for still having low compression could it be the valves guides or valves themself? Any feed back would help Thanks
 

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Master of the Electron
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Welcome to the forum!

The auto-decomp mechanism prevents reaching full compression at starting RPMs... you are likely fine.
 

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Discussion Starter · #3 ·
What is that? And all it will do is turn over and over you can spray gas in the carb and it will start then shut off after it burns the gas. The carbs are getting gas and the bowls on the bottom are filling up just not spraying through the carb
 

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Master of the Electron
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So...
1) Decompression mechanism - the 660's cylinder pressure (due to compression) would be too high for it to crank over with the electric starter so the decomp reduces this pressure at starting RPMs.

2) Have you fully and meticulously disassembled and cleaned the carbs yet? You likely need to.
 

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Discussion Starter · #5 ·
Order the stock makuni carb for it and did a all balls rebuild kits cleaned all the jets and everything still just turning over. What is the compression supposed to be? And could the valves or guides be bad? If so will I need to take it to a shop for that
 

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Your valves and guides could be bad or could be OK. Mine fires up just fine with 80 psi of compression so I would say you need to focus on fuel not compression or valves. If it fires and runs when you spray has in the carbs then compression is not your problem. When you move the choke lever does the cable move?
 

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Master of the Electron
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Does it start and run briefly when starting fluid is sprayed into carb thoats?
 
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