MC-54B-250 Vacuum Tube Diagram

[ludlow]

Hi,

I'm working on an MC-54-B for a friend and I believe it has a problem with the vacuum lines. There appears to be lots of places where there should/could be lines but there are none. I've done some searches but so far have not come up with a diagram/picture of which areas should have vacuum hoses. Does anyone have or know of a diagram that shows correct vacuum line routing?

Thanks

[winchesterboy]

You might be seeing the unused water fittings, used on some scooters but not the 250B, on the left side of the carb. The only vacuum hoses to the carb, if I remember correctly, is to the diaphram on the top right and the fitting to fitting loop on the right side of the carb.

[earlwb]

They may have a couple of fittings on the carb, those are for cold weather climes where they route the coolant bypass line through the carb. This is the coolant line that allows coolant to circulate while the thermostat is closed. Even with the thermostat open some hot coolant flows through the bypass heating the carb.

No one has done a vacuum diagram. But it is quite simple. You have a fitting on the intake manifold (sometimes two fittings). The vacuum line goes to the carb, to the fuel pump, to the PAIR (Passive Air Injection Reactor) system, and to the carbon canistor that recycles gasoline vapors. Depending on the state you are in, the vacuum lines may or may not go to everything.
They may or may not have tee fittings here and there.

There is a larger crankcase vent tube that is routed to the air filter box, and maybe a larger size tube that takes the vapors from the carbon canister and routes them to the air filter box too. On some engines a larger tube may be connected to the carbon canister and routes the air through it to the PAIR air intake filter. many of the scooters, not in California do not have the carbon canister hooked up to the PAIR air intake, so the tube is likely open on one end someplace.

see real simple.

[ludlow]

Thanks guys, I was able to figure it out. I removed the charcoal cannister while I was at it.

Between the vacuum lines and a new fuel pump I believe I've cured the cold start problem. Great info on this site.