Topic: CB5550F weird engine problem - any idea how to solve it?

[TwoTired]

Main jets have a screw based retainer holding them in place. Leak jets are firmly in place. So all is correct

That is true for the PD carbs found on the 77-78 CB550K models.  But, the F model carbs have a leaf spring retainer that holds the main jet in when the bowl is installed, and screw in pilot jets.

I don't know what "leak jets" are.  Honda does not label any of the carb jets as "leak jets".

If you are going back into the carbs, do check the emulsion tubes behind the main jets.  It's often overlooked, but doesn't usually cause cold head pipes.

[kristof]

The black substance turned out to be the old varnish from pressure spring holding the main jet. This was the only part which I forgot to clean. When I was rebuilding carburetors I used dremel with copper brush to clean all the surfaces, carburetor cleaner and compressed air to clean them. As far as I could tell they were clean.

[kristof]

I was wrong labeling the emulsion tubes as leak jets. Thanks for correction.
They are brand new.

[moham]

I thought of one more thing: what's up with the exhaust? Are they 4-4's (or is the F model 4-1)? If they're 4-4's, any chance there is some loose crap blocking the exhaust flow?

Dunno, just trying to think of possible problems...

[kristof]

Sorry for the long delay in updates on my carburetor/fueling problems. As it turned out the problem was more prosaic that I could ever expected.
I used clear vinyl (or whatever they are) fuel lines. They are rather flexible and prone to kinks. I inspected after assembly and did not see any major problems but what happened is that after running and heating/cooling cycle the minor kink in the fuel line became bigger until it blocked it. Subsequently when I was testing I blew air in the fuel lines to see if the fuel is going through and since the bowls on the two problematic carburetors were empty or mostly empty I suspect that I managed to flood two cylinders somehow. So I run out of fuel first, than I flooded cylinders.
I replaced fuel lines with proper fuel lines from Honda which do not kink, blew hot air into the flooded cylinders to evaporate fuel and after that the engine started as if nothing happened. So all is good.

Thank you for your insight and apology for being a blind knob crying about the storm in the teapot  .

Now it would be appropriate to post the pictures of the work and the finished bike  .