Hitchcocks Forum

Hello , looking for guidance/help with issues with my vm24 carburettor. on year 1999 350 bullet

1. only starts on choke
2. bike revs very high when should idle
3. Air screw has only little effect
4. throttle screw has no effect


Items that are ok
1. free play in throttle cable
2. throttle cable free and lubricated and not pinched.
3. throttle slide free and not jammed and shut quickly .

Most likely an air leak between the carb and the engine.

You can test this by spraying some WD40 or similar around the manifold when it's idling and see if the revs increase.

It's very common for the flanges on those carbs to become bent if they are over-tightened against the head. If you take it off and lay it on a flat piece of glass, you'll probably find the "ears" are against the glass and there is a visible gap in the middle you can get a feeler guage in. It'llprobably rock about on the surface of the glass instead of sitting flat.

Solution to that is to strip the carb, stick a sheet of fine wet and dry to the piece of glass with water then circle the flange on it until it's flat again (uniform texture all round). Then clean off any abrasive with carb cleaner and re-assemble with new gaskets/o-rings.

Other sources of leaks are damaged/degraded spacer pieces or gaskets and (depending on how it was set up when new) loss of a blanking screw where an emissions control system has been removed.

This sounds fairly similar to what I experienced with my 2008 350 Bullet. It turned out to be a blocked pilot jet.

would an air leak at the manifold between the carburettor causes high engines rev's ?
i thought that would cause erratic idling and poor starting.

73a wrote: ↑

Thu Apr 14, 2022 8:25 pm

would an air leak at the manifold between the carburettor causes high engines rev's ?
i thought that would cause erratic idling and poor starting.

Leans out the mixture.

It allows more air to enter the intake port by bypassing the closed throttle slide.

Carb slide in the wrong way?

Boofbee wrote: ↑

Sat Apr 16, 2022 6:17 pm

Carb slide in the wrong way?

If it's not air leak as Stinkwheel suggested my money's on the above

Boofbee wrote: ↑

Sat Apr 16, 2022 6:17 pm

Carb slide in the wrong way?

Will it fit the wrong way? Isn't there a slot in the slide and a pin in the carb body to stop that from happening?

Frank

On most carbs the slide will fit the wrong way but won't seat fully