Can not synchronize Honda BF50 - 98 carburetor

[ESa]

I bought an Syncro Motion Pro synchronizer, so far so good. But after done every possible check of the motor,
comp, spark, valves, cleaning and new gaskets in carburetors
the top carburetor stops with double vaccum compared to the other two carburetors. An other difference is that whem I "close" the
mixure screw on the top carb the rpm drops less than the other two carbs. The motor is idling OK but I guess it could be better.
The only difference in the top carburetor, compared to the others, it is slightly corroded.
Could that be the cause of the high vaccum?
PS I have changed the tubes in the synchronizer but get the same result. Any ideas?

 

[jgmo]

Hi,

I'm pretty familiar with these "style" of Keihin carburetors but
I don't have experience syncing carbs on these outboards. So, not sure if I'll be of much help.

The fact that the idle mixture screw on #1 doesn't lean out the idle is troubling because that could indicate that the needle seat has been damaged/deformed. Usually a result of overtightening the mixture screw.

After reading the procedure in the carb manual I have a couple of questions:

Did you clean the low speed jet sets or replace them? If these carbs were badly varnished it can be almost impossible to get them clean. They also have a tendency to crack up the side of the tube.

Are you setting #3 (bottom) carb first and then 2 then 1?

Did you crack the throttle 3 times then reset idle before moving to the next carb?

Errors made at #3 & #2 carb will be magnified when you get to #1.

Do you have the correct (gray/black) decel check valve and does it work properly? Is the arrow pointing towards the carbs?

Did you perform the accel/decel vacuum test? If there's a leak it might explain the higher vacuum in #1. Although I would first suspect the jet set or it's oring. Not sure though.

 

[ESa]

PROBLEM SOLVED!
It was to hight friction between "inner" and "outer" trottle valve arm. I had no control where
#1 carburetor trottle valv was positioned. A little oil and exercise solved the problem with "dead carburetor!
Thank you for your advices. It gave me new ways of thinking. Erik

 

[jgmo]

That's great news!
Glad you figured it out.

Thank you for the update and description of how you fixed it.