I'm going to have to look at the carbs more closely. Thanks for the help.

 

It almost seams like the bike has new rings that are not seated in yet. That is what would happen. They would be tight until the motor warms up causing slow cranking.

I don't understand the slow cranking when cold.

 

So no tight rings when cold, because everything is shrunken. But put a heat lamp on it and it cranks when it should be tighter. Yes, that is bass ackwards.

 

Now that I've done some reading, it's possible that it could be a problem with the valve clearance. No compression = no fire?

 

Cant be valves, without compression the engine would spin over very easy, hot or cold. Have to say your problem is a real strange one but you have definately got compression.

 

I want to say that it is the ignition but that doesn't explain why it starts when the engine is hot. I know the choke is ok, I can hear an obvious difference between choke and no choke when trying to start. One of the cylinders is firing with the choke on. If it weren't dependent on temperature I'd say it is the ignition system.

I checked the starter motor and the brushes are in great condition. I checked continuity per the service manual and all is good. Although, I should probably check the voltage going to the starter.

 

No new rings that I am aware of. I believe the only engine work that has been done is new valve springs, and a new timing chain tensioner. Also a new clutch but that shouldn't affect it.

 

Every motor that I have rebuild is tight when cold until the rings slide on the cylinder walls better. I guess it depends on the expansion rates of the cylinder walls and the pistons. The older Chevy motors in the '60's had warm engine cranking issues because the pistons would expand. It was not mentioned that this engine was rebuilt either.

The loose valve thing may be on to something but usually happens on push rod engines. Valves tend to tighten up as the engine warms so I would personally not think this is the problem, not to say that it isn't.

The starter clutch still sounds suspicious.

If it is not choke related, something is expanding after being heated giving more clearance or slop letting the engine spin freer.

 

Another thing. Does anyone know what the purpose of the two black T's on the top of the carbs are for? I'm guessing some kind of vent. I believe I found the tube that is supposed to go to them but the tubing is rotted.

 

The starter clutch was replaced with one from a working bike that was parted out.