Dead Cylinder but has compression spark and fuel?????

the only thing he has not confirmed that he tried was swapping the plug wires for 2 and 3. it could be the plug wire connection at the coil has failed

 

If you put your hand over the back of the #3 carb it will start to run. What that does is force the pressure change in the carb, leaning up the air and making the fuel mix going into the #3 cylinder richer. #3 will not run on idle but will it will it run on 1/2 throttle or full throttle? If if you have IR temp gauge you can check the exhaust header while you are testing and not burn your hand.

I know us coming back to fuel issues is driving you nuts, but if you have compression, you have spark, the only think it can be is the fuel. I would mention valve spec but you said the compression test is good. I wish you luck on finding this problem.

 

I had a similar issue with the 550 and it was the secondary fuel supply tube from the bowl. Clogged solid from debris after a full rebuild and an initial run period. Does the 650 have that as well?

 

the brass rod for the enrichment circuit yes hatachi and mikuni have then and the wells in the carb bowl. at some point the cylinder should run as pilot jet would work once bike was warmed up

 

I had a similar problem and it turned out that about 1/2 of the intake gasket was missing, causing a big air leak. Replaced the gasket and that solved the problem.

 

Was the plug wet or dry?

 

Dry. Too much air.

 

In this case the plug comes out wet so either the float is not shutting off the bowl, the idle circuit is partially clogged or it's a spark strength issue.

 

Just a thought ,pull carbs swap the emulation tube with another from the carb that is "hot", swap the needle and seat and float and same with jets ...put carbs back together and reinstall and see if this "fixed" cold cylinder and problem went to the other cylinder. ...one other item open fuel bowl drain screw , measure how many cc's of fuel is in each bowl if one is low compared to the other float level could be off.

 

maybe he should just swap sparkplug wire on 2 and 3 and see if the issue moves before ripping out a non removable part from the carbs

 

What is he talking about when he says "the #3 Carburetor "air collection port,"" ?

 

the kidney shaped port at the top of throat airbox side of the carb that feeds the air jets. if covering this hole makes bike run better he probally has a vacuum leak

 

Thanks. Didn’t know what he was referring to. Strange that his plug is wet but enriching it makes it run.