Motorcycle - 1981 honda cb750c dohc 4 carbs keihin.
Cylinder 3 is not firing, motorcycle starts up fine with 1,2 and 4 firing. Just cleaned carbs by hand, did not use ultrasonic cleaner.
Spark plug on 3 has gas on sparkplug. Not sooty or oily.
Cylinders 1 and 2 are my best ones with lightly brown spark plugs, issue is not ignition coils. Have not checked spark plug 4 yet.
Alll valves are within tolerance.
Just put a brand new battery in.
I'm taking carbs tonight to be professionally cleaned and buying a compression tester.
Anyvother ideas on what to do?
UPDATE: 8/13/2018 Sorry for the extreme delay in response. Been hectic with getting married, finally had time to work on the bike.
What I did to try and solve the problem within the last week, after my initial post.
- I replaced the ignition coils , spark plug wires and boots. With this I checked to make sure the coils were good and measured both primary and secondary windings before putting onto the bike.
- rechecked valve clearance and all were within tolerance
- did (cold) compression test. cylinder 1 150 psi, 2 150 psi, 3 145 psi, 4 150 psi.
- spark plug 3 does get spark after putting the new coils on. its a solid white color.
I do not think there is a significant lack of compression in 3 there is more of a probability I was not holding the tool on the spark plug hole well enough. I had to use the push down tool, I could not get the compression tool to screw in properly.
After all this I still could not get cylinder 3 to fire. I'm left thinking I need to get the carburetors professionally cleaned.