2002 50TLRA surging

[99yam40]

as stated, BIL's 50 is surging getting up on top and running,
idles well.
thought maybe pump was leaking into #3 causing it to miss at times, but it comes and goes
Fuel pump is not leaking out of pulse port.
did not see any difference on plugs.
I went thru the carbs about a month ago
what else should I look for?

[panasonic]

I would look at the fuel supply to the pump since you already went through the carbs.I know you probably already tried a different portable tank on it.
I remember working on a older 15 years ago and it was what I called surging as well. Cleaned carbs, tried different fuel tanks, checked timing..all the usual stuff. Turned out to be the fuel line quick connect fitting on the engine was sucking air.

[99yam40]

thanks,
yes I hooked my tank and fuel line up to his also with same result.
I was also thinking of hooking a clear tubing on the output of the pump to see if I could see air bubbles, but he took it back home with him.

that oil tank sure gets in the way to do things on that 50.
pain in the a$$ to even get to the bolts on the fuel pump, much less the line in and out of it.

I guess I could have disconnected my hose or his from the connector and hooked the fuel line directly to the filter or the pump to eliminate those connectors.
I will see if he still has not taken it to a shop yet and try that this weekend.

he said he tried pumping his bulb and it did not help any, but I should have tried with mine as it is easier to pump. His is very stiff/hard to pump.
pressuring it with the bulb should eliminate sucking air in at those connections.
may take my timing light along also just to watch timing and also spark on the plug wires to see if one may be dropping spark when RPM drops.

when I 1st got my C40 I had problems for a long time similar with high speed missing.
turned out a previous owner drilled out the main jets causing too much fuel.
I found that by running with the cowling and silencer off,
as long as I ran into the wind it ran fine, turn around and run with the wind it would start missing again.

I guess if the rubber plugs over the pilot jet holes were to fall out, it could draw fuel from both places and run too rich.
All fuel should have to come thru the main jet before also heading to the pilot jet