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Discussion Starter · #1 ·
Hello all. I am currently turning a 73' CB450 into a cafe racer. I've run into a few snags along the way. Rebuilt a starter, replaced clutch springs and caps. Motorcycle runs, but I discovered that one cylinder compression tests at 0 psi. So, I checked the valves to make sure they were all at least moving and they are. I can tell that the exhauust valve looks like it's oil fouled. It's not just carbon, it's greazzy. My next thing to check is the valve clearance and then on to removing the head and checking for more serious problems. 2 questions.... 1, am I missing something that I should check before I actually tear into the engine. 2. Any way to get a downloadable factory service manual online. I couldn't find a used one. Thanks.
 

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Sensei
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At 163 PSI (minimum spec) you (are supposed to) tear a 450 down to replace the rings..... At 0 PSI you'll have to tear it down to verify "Why?".......
 

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Discussion Starter · #3 ·
My hope was that the tappet was too tight and that the valve was not completely seating. Maybe wishful thinking, but I'm trying to avoid tearing into it if at all possible.
 

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Sensei
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I guess a tight tappet is a possibility, but that would be easy to verify.... Check with the feeler....Or your fingers.....
I'd be more worried it was a slightly bent valve not seating correctly....Of course...That's teardown time again.....
What is the compression on the "running" cylinder?
 

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Discussion Starter · #5 ·
Yeah, that's another piece of bad news. The running piston is only at 90 or so. I was actually suprised that it ran so well. The bike has 19,000 original miles on it and it has clearly been sitting out somewhere for quite some time. Like I said just hoping to get lucky with the tappets, I assume I'm going to have to tear into it. Any great ideas on a factory service manual other than Amazon?
 
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