M-25 carb.

[carleton lathrop]

I've got an M-25 on my '40 knuck. Someone told me to make it run good I should use a 1.125" venturi, but don't I have to change some other parts such as jets, etc? any help would be appreciated. AMCA membe, Carl

[Jerry Wieland]

Cotten swears by opening up the venturi on a M-25 but I have had good results just leaving them alone and getting rid of all vacuum leaks. It probably cannot hurt to give them more air. Sometimes tuning a Linkert can be a trial by fire thing and you just keep working at it til you get it right. I would think everything else should be fine with a venturi change.

Jerry

[T. Cotten]

Carl!

My copy of Palmer's lists a 1 5/16" venturi for the M-25,
so 'someone' advised you to go smaller than 'stock'.

For breaking in a motor, or pulling a hack, that would have its benefits.

The M-25 has no fixed jet, and the main nozzle is essentially the same as for models with the 1 1/8" venturi.
So venturies can be swapped at will, as long as they properly fit.

For a limbered-up solo machine however, particularly with today's higher road speeds, I would advocate the correct venturi. And an M-75 nozzle if you can find one (second from left in attachment.)

....Cotten