checking tillison pop off pressure

[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.