checking tillison pop off pressure

[David Luciani]

it's in the carb rebuild section which is very thin on oinfo in this forum. at some point i'll start repopulating the info as i remeber it.

on where i find stuff
honestly
i have no clue.
when i';m donking around on the computer i often wander off into areas just following a search thread series.
i'm free lancing and free associating ideas as i go.

if it's interesting enough i'll post it and maybe add the tiny bit i know my own self.
of course as soon as i leave that thread i forget it.
after all i posted it so i can find it again later in the forum!!
which is why losing data on other forums is sooo annoying.
redoing those threads actually requires me to think and remember what i did in the past.
a skill i absolutely suck at!!

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[doug tenney]

E.C.'s instructions on fulcrum height seem vague to me, because I don't recall where he's measuring from: the as-cast bottom of the dished area, or the machined gasket surface?  I'm pretty sure he's referring to the machined gasket surface.  You can lay a stiff ruler across the surface and measure the depth with you caliper (but first zero out the caliper on the ruler's thickness.)

As far as a good pop-off number: with a single HL on a 100cc motor, IMO you will have enough air speed (and therefore venturi vacuum) that a broad range of values would work.  Just put it together with the parts it came with and it should work.  If you measure it, I'm thinking anywhere from 7 or 8 psi to 15 psi.
As Steve O pointed out, there are nuances to this, but this should get you running.

Too low and the fuel pump will sometimes overpower the inlet needle, and cause flooding.
Too high and the motor will "stand up" like it should when you whack the throttle open, but will promptly die 1/2 second later.

[Mel Ruffner]

Thanks Doug for the replies I,am to a little confused as to the fulcrum measurement

[David Luciani]

lay a straight edge on machined gasket surface and measure.
or buy the pre-made gauge ec carb sells be sure to get correct fuel application .

[Terry Bentley]

I know this is an old thread, but....... The HL-237A as mentioned the one in question is a factory alcohol carburetor. Originally it would have come on a Komet K-99. This engine had two of them on a factory dual manifold.

That is why it has a nylon needle. The only other applications for a plastic needle is early chainsaws. But the needle seat has a lot smaller opening.