FH641V-BS15 SLIGHT SURGING IDLE TO MID RANGE

[Convert]

Looking for some input to track down the surging issue .

Just started last week after I refueled the tank. Maybe some crud got through the older filter so-

I changed the fuel filter slight improvement, next i changed the fuel pump -no changes surge continues,

Coils are new, air filter new, sparkplugs are new (last six months). High speed throttle little to no surging.

I think that my next move is a carb rebuild.

Any thoughts?

Thanks
Tom B
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[bertsmobile1]

Next move should have been the first move
Surging is usually insufficient fuel to maintain a constant speed
Surging at idle but not WFO = blocked idle circuit

 

[StarTech]

It might need a slight adjustment to the idle mixture screws. These are access after removing the welch plugs covering them. On the following image the needle (PN16187-7002) are under the welch (PN 92066-7009).

 

[Convert]

Thank you for your input

Tom B