Cox TeeDee part ask

It's a pressure nipple. Basically it's closed off in stock form. To utilize it you would need to drill through it and the crankcase.

It's better to tap the backplate and run pressure off that. Plus it's reversable.

Ron

That sir is a nipple for use IF you want to use a pressurized fuel delivery system (crankcase pressure).
The supplied Cox instuctions give you information about drilling a hole from that point into the crankcase itself. (As supplied, this hole is started but NOT drilled all the way through into the crankcase.)
This idea was not very well thought out because it's difficult to get a fuel tube to stay on that small of a smooth plastic pressure nipple without leaking or falling off. A leak here causes very bad running.
The Cox TD instructions also talk about drilling out the venturi larger (for more power) IF using this pressure system. Using this (relatively high) "timed crankcase pressure" can make the needle valve very SENSITIVE to set.

So, what some users do is put in a pressure tap (from other engine manufacturers such as K&B),
into the engines backplate. The pressure hole ideally should be ~ .010 - .015" in diameter. This allows for mild crankcase pressure which makes the needle valve setting much less sensitive.
The late Joe Klause of Kustom Kraftsmanship offered backplates with this already done.
Sadly, they are no longer being made...

Cheers, Paul

ah, ok.
Now i understand what is it.
Thank you!

Welcome to the Forum !!!!

Sometimes it is just used is as a peg to secure the spring starter.
Al

@Big Al:
oh, thats a great idea with the spring starter

@Kim:
Thank you