I have a used OS 25 S engine.  The tank is a Haye's tank, mounted on a Shark 402.   It starts fairly easy. Then it runs, cuts off, runs, cuts off - It ran most of a tank that way last night.

So far, I have put foam behind the tank and changed the Fuel Filter.  Haven't tried it yet.   Have any of you had this problem and what was your fix?

     Hi Allen:

     Sometimes it is the small things that confuse us.  I have had this problem in the past and I have found that the engine was not getting enough fuel.  It has been a faulty nva and sometimes my fault.  I was asleep at the switch and failed to notice that that particular engine needed the needle opened many turns to get the engine to run correctly.  Take a walk on the wild side and try replacing the nva and/or opening the needle many more turns than you think s correct. These engines are very simple and it is us who are misinterpreting what they want. Let us know what you find to be the solution.

    We are having a club stunt contest, old time pattern, and a club combat, run what you brung,  contest this Summer.  Nothing high tech but just a FUN get together.  Would like to see you join us.  Remember, it is a very easy trip for you to attend our new flying site.

                                                                                                          Be well,

                                                                                                          Frank McCune

I am planning to take the needle out.  I want to look at the clunk also.  I am not running pressure but it is uniflow.

Has anyone ever had a Hayes tank develop a hole?

Well, I washed out the NVA with alcohol, changed the tubing inside the tank to the original kind - more flexible.  I changed the tubing and fuel filter between tank and engine, as well as putting the foam behind the tank.  My suspicion is that the tubing in the tank and the tubing connection to the fuel filter were faulty.  It worked! Today, two flights until the tank and motor came loose.  That's an easy fix.

Thanks to all. 

P.S.  This plane, - a Shark 402 - cuts tightly - actually felt a bit like it was over controlling.  I had it on 52 ft lines.   

I did another flight since the last post.  However, I had worse runs.  The back top mounting bolt would not tighten or stay tight so I have replaced it.  Hope that cures it.

Maybe that's been the problem since the beginning. Were the threads worn out? Does it have aluminum or any sort of bearers between the engine tabs and the beams?
Rusty