Compression and Valves

Posted by timpetou on Sep 04, 2012; 2:55am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Compression-and-Valves-tp4028598.html

Hi, after taking advantage of this forum for the last couple of weeks this is my first post. So, I bought a 79 CB750 a month ago and after a 100 bucks worth of beer and another couple of hundred in parts in I am at wits end.

Here's what I'm dealing with. The number 4 cylinder seems to be hotter than the rest, there is considerably more and hotter exhaust coming out of that pipe too. When I crank the throttle real quick there is a it doesn't rev up right away. It loses power past 4000 RPM and that prompted me to check compression and valve clearances. The results are: 140(4), 140(3), 140(2) and 30(1). Number one didn't change when I did the wet test.

The valves checked out like this

1: Intake 0.04, 0.04               Exhaust 0.13, 0.13
2: Intake 0.06, less than 0.04  Exhaust 0.09, 0.09
3: Intake both less than 0.04   Exhaust 0.05, 0.05
4: Intake both less than 0.04   Exhaust 0.23, less than 0.04

What I did so far:

new battery
new spark plugs (have spark on all 4)
cleaned carb (twice, dammit, after using gasket sealer that turned into fun little black snowflakes )

Now I am wondering, what the fuck is going on? Are my valves responsible for all that trouble?