Out-of-my-league manifold question

[T. Cotten]

Please explain this lever!

Thanks in advance,

....Cotten

[tfburke3]

Please explain this lever!

Thanks in advance,

....Cotten

Intake manifold gas primer petcock?
Tom

[T. Cotten]

Maybe Tom,

But then why put priming cups on the cylinders?

The only thing I would bet on is it has vacuum leaks,.. if it connects at all?

....Cotten
PS: I've never encountered an "auxillary air valve" thumbtab like that either.

[exeric]

On early H-D twins up to 1914, they offered an auxiliary air valve built into the manifold. Perhaps this is a homemade version of that. The manifold in the first picture is a straight 1916 and earlier H-D twin manifold. Shortly into 1916 H-D went to the curved runner manifold. Tom, I thought the H series Scheblers had an auxiliary air valve.

[pisten-bully]

possibly a shut-off (this is assuming that flipping the lever blocks off the manifold T to the carburetor)

[T. Cotten]

On early H-D twins up to 1914, they offered an auxiliary air valve built into the manifold. Perhaps this is a homemade version of that. The manifold in the first picture is a straight 1916 and earlier H-D twin manifold. Shortly into 1916 H-D went to the curved runner manifold. Tom, I thought the H series Scheblers had an auxiliary air valve.

Eric!

I have yet to encounter the real thing, and would appreciate a pic if possible.
It had to be a problem in itself.

Earlier HX had no auxillary valve (example attached); This '16 appears to have something added to the thumbtab.
(I use buffalo nickels.)

And Harry!

I am having a hard time imagining why that would be an advantage.
Emergency brake?

....Cotten

[pisten-bully]

Emergency brake?

Jake Brake! No, I thought magneto machines were shut off by grounding or opening a compression release, so shutting off the fuel/air would shut off the bike... just guessin' here Cotten!

[exeric]

This is a 1914 manifold. I really don't know how the auxiliary air valve worked. SloJoe would certainly know as I believe he was reproducing this manifold.

[Tommo]

1915 Electric models had a vacuum take off in the centre of the manifold to operate the switch in the generator that completed the electrical circuit.
As far as I'm aware HD used these manifolds with a blanking plug in the hole during 1916 until they ran out of stocks of them and then fitted ones that hadn't been drilled for the vacuum take-off.
I don't think the priming cock is a factory fitting but you can never be 100% sure of what could have happened at the HD Factory back in those days.

[Robert Luland]

Maybe a race bike innovation? Who want's to be dicking around with cylinder primers on the track when you can have a one time dump of raw fuel straight into the manifold. Bob L

[T. Cotten]

Thanks Tommo!

My 'internet' literature says the manifold changed dramatically mid-'16, both thread and direction of thread.
So the manifold in my first photo is even more enigmatic in that it is not 'screw-on', but has a flange.

....Cotten

[exeric]

I thought all 1916Js were flange type, bolt on manifolds. This picture is of an early 1916 motor that has been over-restored, but probably from a very complete original. The cylinders tell the tale as you can see how the fins wrap around the exhaust valve covers. That was a 1915, to early 1916 feature.

[exeric]

I did a bit more research and according to Terry Marsh, the HX95 is the correct carb for a 1915 H-D; and that is a bolt on carb, not screw on.

[T. Cotten]

Bolt-on is good, Eric!

...Cotten
PS: I need to have a pipe-thread to left-hand-whatever-thread adapter cut.
All my real machinist friends are having too much fun doing other things.

[Tommo]

Eric I thought most if not all of the 1915 cylinders were not rounded off over the top of the screw that locates the inlet cage.
I have a nos pair of 1915 cylinders and they are square across the top of the protrusion that the screw goes into.