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Fighter Fanatic
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43 Posts
Discussion Starter #1
My 88 CBR 600 Hurricane wont start so I bought a compression tester to make sure it had enough. I removed all of the spark plug wires and left the plugs in. But when I run the test it only gives me 60 Psi. Spec says 185 +_ 28 Psi. I only tested two of the cylinders so far because i thought i was doing something wrong. The bike was running before I broke it down to the frame but it would take forever to start and you would have to jump it with a car before it would fire up. Is there anything i am not doing right. I don't think it is the tester because I did my 85 VT500 Shadow and all the way cooled down it showed 120 Psi. Any help would be appreciated. Thanks guys.

P.S. the headers are on but not the can and the engine was never disassembled.
 

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Fast ZX-12R
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17,522 Posts
It's kind of odd that both cylinders read the same. 60 psi isn't very much, thats why it won't start unless you crank the hell out of it. Can you see any leaking around the head gasket as in blown? Does it smoke, lack power when it does fire up?
 

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ShamanFighter
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22,340 Posts
pour some oil down the plug holes to see if compression picks back up if it does you might have ring problems
 
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n00blet
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Even with good rings compression will always go up with oil.

Did you hold the throttle open during the test? Many forget and get false readings.
 
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Registered
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Remove ALL the plugs, fit the compression tester, and hold the throttle wide open, spin the motor over a couple of times and note the readings across the cylinders. Then drop a few mil' of oil down each bore and repeat the test.
If the readings only rise by a small amount 15psi or so then look at the valves, if it rises significantly then look at the rings/bores.
If you valve clearances are closed up it will lower the compression as they will not seal correctly. Check all your valve clearances are within the manufacturers specifications, and then repeat the test.
If you have access to a compressor then get yourself a leak down test which will tell you how much the afected cylinder is leaking.
 
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