Ok, I'm running a bladder on my os la 15 with a fox universal needle valve. Right after the needle comes the bubbles. None before it just right after. I just put the thing in water and put pressure on it, no bubbles. Then pulled a vacum on it and no water came in. What gives here?? I'm puzzled. Sure can't get a good run with an engine you can't adjust. Any ideas?? Thanks, Eddie Fulmer

Eddie,

If you're using a high pressure bladder and not using any kind of pressure reducer before the needle valve then you are probably experiencing a venturi effect that is sucking in air around the o-ring and threads. Some RNV can do a better job then others at not doing that. Appearently yours can't handle the high pressure directly. If you don't want to use a pressure reducer before the RNV then you might use the RNV that came with the OS 15LA. It doesn't seem to be affected by being fed the high pressure fuel directly into it. Lou had the same problems you described because he doesn't use a pressure reducer and so he simply uses the original LA RNV after it's been cut off the backplate. I believe that he tie raps it behind the engine. You can read Lou's discussion about the problems he had at his web site [link=http://www.georgiacombat.com/]GeorgiaCombat[/link] . If you want to continue using your Fox RNV then make yourself a pressure reducer. You'll find a simple one to make in my article on using bladders in the workshop section of my web site [link=http://www.texascombat.com]TexasCombat[/link] . I've never experienced the problem and I use the OS replacement RNV that Lou was having problems with, but I use a pressure reducer on my system.

Thanks for the info. I replaced the needle with the stock needle that comes with the OS LA. I now have a fine running engine. I cut the valve off the new backplate and mounted it with a tie wrap. No more bubbles.

THE needle to use is the one that came with the OS 10FSR. Fine threads, easy adjustment. Most of the needles used in the old OS FP series engines would work, too. If there's an air leak in the needle assembly, the fuel leaks out rather than air leaking in. Unless the fuel line after the needle doesn't fit well.

If you have a leak, seal it by putting a short length of neoprene tubing around the needle. Or use teflon tape.