Black Widow Crankcase hole?

'Long time ago people would tap the case there on the corner for fuel tank pressure. The taps I've seen were much smaller holes than what you've got. I don't know how well it would work, but you could put a check valve in line with that pressure tap and see how well it works for you. I don't know if the tap would siphon off enough back pressure to make the reed float, but you never can tell until you try. I'd put the check valve in line, fire it up, and see how much the pressure pulses blow against your finger. Log the max RPM, then block the tap and see what you get for RPM with the hole blocked. That'd tell you how effective it would be as a pressure tap.

The Geezer Mark

With a hole that size, it's unlikely you would build up enough crankcase pressure to get the engine to start.  However, one technique that was used to get a small hole was to embed a tap, usually brass, in the case in the location shown, then with a very small diameter stainless steel wire centered in the tap, fill it with lead solder.  After cooling, the wire was pulled free leaving a sufficiently small hole to allow enough pressure for the engine to run, but to also pressurize an attached tank.

I've never tried pressure with a reed valve, but have used tapped backplates on NORVELs.  I've attached a pic of a tapped backplate for a NORVEL.  This backplate is essentially the same size as the rear crankcase cover for a TD .049 so you will have a reference for the tap hole size.

I have done that with several reedies. That  works very well. I would recommend filling the tube with solder or J B Weld and then drilling a smaller hole with a #80 bit. A one way check valve is usually a good idea, too. I think I have a video on my youtube of a pressurized reedie running. The fuel tank has to be closed/unvented except to the engine feed. The pressure from the crank case positively pressurizes the fuel tank.

Just wondering where you got that. I gave a tapped BW case to one of the younger forum members several years ago. I can't remember his user name but I think his name was Matt.

fit90 wrote:Just wondering where you got that. I gave a tapped BW case to one of the younger forum members several years ago. I can't remember his user name but I think his name was Matt.

It was in a bunch of parts and pieces shipped from Garland, Texas !

Garland, TX is where the zombie apacolypse starts in Zombieland. Glad you got it out of there.