Dead on cylinder #1

[ScottBowl]

Hello people!

I just finished a head gasket replacement on a cb650.

I seem to have a dead cylinder (#1) now. When I pull the boot off of the spark plug, the bike idles no differently. If I remove the spark plug for cylinder #1 and ground it, it makes good spark. The bike runs, but sputters out of the pipe for cyl #1 & 2. The head pipes for cylinder #2-4 are really hot whereas the pipe for #1 is just warm.

This leads me to believe my timing is off... Or the carburetor for #1 is just too lean or too rich to the point of not firing at all?

When I re-installed the camshaft, I turned the engine to the 1.4 T mark and aligned the camshaft so that the index mark faced towards the front of the bike. My question is, if I set the timing incorrectly when I put the camshaft on, would the bike even run at all??

[Folsoml]

What is the compression like on this cylinder now?

[ScottBowl]

Took the carbs off, I may have found the cause.

This hose is slashed!




further observations:

Airbox boots are wet, #3 cylinder boot wasn't properly fitted on the carb.

[ScottBowl]

What is the compression like on this cylinder now?

I do not have a compression tester currently

The hose in the picture seems to attach to the airbox. Is this something I must replace in order for the bike to run properly? I imagine so, but I wonder where I'm going to find it

[Folsoml]

This is a vent hose. It allows fuel to flow into the carb bowls. Fuel will leak out if this is not in place. It is doubtful that this would be the reason #1 is not working.

[Volker_P]

Camshaft timing would affect all four cylinders and it won't run nicely if you get it started at all. So probably all right. What about valve settings?

The hose shows a cracked T-vent, a famous issue that may cause problems like carb overflow or just make no difference. However it seems not to be known as a reason for not firing at all.

Please also have a look what I wrote in the very similar problem in the 1981 CB650 #1 Cylinder not firing thread.

[ScottBowl]

Camshaft timing would affect all four cylinders and it won't run nicely if you get it started at all. So probably all right. What about valve settings?

The hose shows a cracked T-vent,

Please also have a look what I wrote in the very similar problem in the 1981 CB650 #1 Cylinder not firing thread.

Wow, his issue is nearly identical to mine! Thank you, I'll be watching that thread closely.

[ScottBowl]

Compression test showed zero on cyl#1.

Opened valve cover, turned engine over, 140 psi.

I found the problem... There are two bolt sizes for the outer valve covers. I put the long one in where the short bolt should have gone. This bolt interfered with one of the valves on cylinder #1... Pretty embarassing, don't do what I did; pay attention to detail!

Runs great now.

[Folsoml]

Glad you found the problem!