Well, it's been three weeks since I started flying, everything is going pretty well, only a few repairs needed so far.... But I have a question. There are small air bubbles in the fuel line between the "remote" needle valve and the carb. If the engine stops, it only takes a few seconds for this part of the fuel line to empty of fuel. There are no bubbles from tank to the valve. Is it worth the trouble to get rid of the remote needle valve and replace it with a vavle at the carburetor? Is this a part that can be purchased? I tried tightening the connections of the tubes to the needle valve, wire tightened at each location, but the bubbles are still there. I think they caused one stall and a small crash, at least that is my story and I'm sticking to it!! Any information on replacing the remote needle valve and if it is possible would be appreciated! The engine is an OS 40LA, with only four or five hours on it. Thanks.

Be on the lookout for an old OS 40 fp engine. The back plate (aluminum) and carb (with front needle valve) are interchangable with the LA, and will turn your LA into a much simpler, solid, and more reliable engine.

Yea, I feel the same way. Those remote needles are garbage. I have had nothing but problems with them. The early ones don't hold the fuel line on and the new ones leak like crazy. I won't buy another OS if it has one. There are too many other engines out there that don't have it. I know they are supposed to be safer, but they have been in the carb for many years, they should have left them alone. I have 2 91 FX engines that do the same thing you are describing. I have to find a carb that works on them.

The OS carbs can't be converted, but some carbs can be. Magnum RNV carbs, for example, can be converted easily to "normal" operation.

You can buy older-style OS carbs that will fit, or other makes of carbs if you really want to.

That said, I haven't had any problems with my RNV engines, and I've seen a lot of guys flying them with no problems at all. I haven't seen air in the line between the RNV and carb, so I suspect you have an air leak somewhere. And an RNV carb will act exactly like a normal carb with an air leak, all kinds of things won't work right. Find the leak, and you should be ok.

fwiw, I don't care much for RNV either, I converted all my Mags to normal operation, and would convert my OSs as well, but it's too much trouble, and they do run fine for me.

I had the same problems with bubbles seemingly originating in the RNV. I tried changing the little O-ring on the needle valve, but no better. I put zip ties around all the fuel outlets (nipples), but no luck. It turns out that I had inadvertently round down the tiny lip on one of the nipples, when my screwdriver ground up against it as I was trying to tighten one of the engine mounting screws.

Don't give up! Try the things I said above, and good luck! I was going nuts over this.

ANOTHER good reason to hate RNVs! At least on the OS .46 FX, the RNV (and tube) get in the way of the engine mounting screws. But I don't understand why the zip ties didn't take care of the problem.

I've had little bubblies with my OS .46 FX. I put really clear tubing between the tank and the needle valve, and the bubbles were definitely coming from the valve, not the tank. But it only happened when I accelerated quickly from idle to full open, so not a big deal.

Since the needle valve that goes into the carb seems to be exactly the same as the needle valve that goes into the RNV, with the exact same O ring, it would seem to me that both probably suck air exactly the same, it's just you can't see it with the carb-mounted NV.

I don't know if I said this, but my engine is also a 46 FX. I had a hard time finding clear tubing. Tough to see little bubbles through the blue tubing. Oh well.