Hi Yoyo27983,

I really haven't worked with the RNV (rear needle valve) assemblies too much and so I'm not very knowledgable, perhaps someone else can jump in and help us out here. I'll give you my thoughts and I hope they help.

If there is never air in the line from the tank, to the RNV but air appears between the RNV and the carb, then I would suspect an air leak, probably around the needle valve itself ("O" ring?) or one of the fittings.

The GMS .47 has had air leaks around the carb and backplate and this may cause idling and mixture problems. There may be a little air leaking out the front bearing, and this is normal.

To test:
1. Remove the muffler and put about 1 foot fuel line onto the rear needle valve intake nipple.
2. Back out the rear needle valve to get reasonble air flow (about one turn open from normal flying), open the carb fully, put your thumb or finger over the carb opening (throat) and block the exhaust opening with another thumb/finger.
3. Blow into the fuel line and listen for any air leaks. To isolate leaks, either spray area with soapy water (or carefully partially submerge in water - don't let water in the carb or exhaust opening - if you do - dry thouroughly and re-lubricate) and look for bubbles.

If the carb body is leaking where it goes into the crankcase, or the the back plate is leaking, it can be sealed with a small amount of RTV (room temperature vulcanization) such as Permatex Ultra Copper or something similar when you reinstall. It is like silicon sealer, will take heat and usually available at the local auto parts store.

Hope this helps.

Fly4Fun,

Wayne Miller