M51 v M55

[Tommo]

A bit of quick research in Bruce Palmers book shows that internally both carbs are identical.
There are two external differences one minor but one is a major difference.
The minor one is the throttle lever 1238-36 / 37 / 40 depending on application.
The major one is the carb mounting flange with one being 3 bolt and the other being 4 bolt.
I'll hold my hand up and say knuckles are way out of my league and what follows could prove to be wrong but here goes.
The M5 fitted to 1936-39 knuckles I suspect was a 3 bolt mount and as most part numbers for the inlet manifold change to -40 part number in my late model parts book I'm led to suspect that that is when the 4 bolt manifold started.
Robbie or some knuckle guru help me here.
The main point here with regard to Steve's bike is that I'm at a bit of a loss to understand how a 4 bolt mount carb is fitted to a 3 bolt manifold. Who knows, anything's possible
Does that answer your question kitabel

[Rubone]

Tommo, an M55 is a three bolt carb.

[Chris Haynes]

The M55 was the factory replacement for the M5.

[kitabel]

A bit of quick research in Bruce Palmers book shows that internally both carbs are identical.
Is that what he actually said? Or the conclusion that you draw from his commentary?
No, they're not.

[T. Cotten]

From those that crossed my benches, Folks,...

Other than a different main nozzle,
The two differences that come to mind are that the M55s did not have the 7-64 bowl, nor were the bodies nickel, as were pre-War M51s.
Post-War differences escape me without an M55 currently on the bench.

Some of you may have noted that the Pre-War M51s were milled and drilled to accept the OHV bowl.

Just wanted to get those out of the way, thanks.

....Cotten

[shinedogg]

My M55 has the early bowl with the cast #, no drain plug and is 3 bolt.