mac 1-51 fuel issue

[gunnarfan]

got the beast to wake up. had it running for a bit. swapped off the fuel line as the old one had a hole. having issue getting the fuel to take up into the line... what do ya think? carb adjust? it was just cleaned. fuel pump? haven't had to frig with that sort of thing yet.

runs great with gas in carb!!

might just trade off as is to one of you racing freaks!

 

[PES+]

How did you clean the carb without disassembling it?

 

[HiOctane]

If she only burns only the gas you give her,then you have to open the carb and clean it .Check if the inlet needle doesnt stick.Get some new gas if old.Have you got a felt or screen on the hose ?They are pretty easy to work on.

 

[gunnarfan]

i'll admit it.. i cheated. i let my neighbor clean it.. hes out of work for medical reasons and i like to give him little jobs to do. he claims to have had a guy take it apart and work on it. may just be a case of me having to do it myself.

fuel filter is felt.. guess i'm going to open up the carb myself.. the guy could have always fibbed.

 

[dtnodya]

Explain further ...

You say you "had it running for a bit" .. Does that mean that it was running on its own or just when you pour gas down the carb?

Is the gas making it to the carb? When you take the line off of the carb does gas come out?

Could be many different things ...

 

[Ancient One]

Usually the carb requires a rebuild on the old macs: New fuel pump diaphragm, gaskets, needle & seat, clean the internal fuel filter. Fuel pump diaphraghm on these old saws stretches with age & will not pump fuel. Also check the pressure port to the crankcase, the fuel pump works on a pressure impulse from the crankcase.

If the carb has been apart, and the gaskets & fuel pump diaphragm were removed, chances are they were not "clocked" correctly when the carb was assembled, blocking the ports.

Gasket beween the carb and the crankcase may be installed wrong, blocking the pressure port. Some macs have a spacer and two gaskets between the carb & crankcase, check the pressure port holes and make sure they line up. If the gaskets are hard, you may be leaking air into the crankcase, or the impulse port may not be sealing.

Sometimes the hose in the tank is damaged or the filter on the end of the hose is plugged.

If the saw tries to run when gas is squirted in the carb, then dies, fuel pump diaphraghm is usually the criminal.

 

[gunnarfan]

yeah.. that diaphragm was stuck right in there. bought the last kit at the local distributor. turns out the guy that "cleaned" it used an air hose and did minimal cleaning.. glad to learn who not to use and always glad to take apart new types of carbs.