Mike, Mike, Mike (Austin),
I'm the guy that helped you at the LARKs contest. I can't believe you're returning the Webra. It was running great after we worked on it at LARKS. Excellent low idle and good transition. The problem with yours before we tuned it was that it was way too rich on the low end. Have you flown it since? Have you had problems?
I have two Webras (actually one's the Bully with a two plug head, but otherwise the same engine), and both run like horses (if you know how to tune them). BTW, I have the standard carb. Mike, you've seen mine run at two contests, I never have any tuning problems. In fact, with the exception of richening it a click or two as it's breaking in I never touch the needle.
glowplugboy, I don't really think it's fair that you're bashing this engine. With all due respect you guys simply didn't know how to tune it because you're experience isn't with pumped engines. After your 12 hours of unsuccessful attempts it only took us about 12 minutes to get it running great at Larks. And if you noticed there were about five other guys standing around that all knew exactly what to do to get it to run correctly. That's because they're familiar with engines of this size and pumped engines. Hey, honestly, when I first got this engine I was puzzled too until one of my flying buddies that has flown them for a few years told me what to do. After that I had no problem.
Here are the key points I've found with this engine.
1. From the factory the pump pressure is almost always too high. I had to back the pump pressure off of both of mine. That means turning the pump screw counter clockwise. I ended up with about five or six threads showing. I think I backed off 1 to 1 1/2 turns. Start at 3/4 turns out and then slowly move it back until you don't have any flooding problems. When the pump pressure is too high what you'll notice is that you can practically have the high end needle closed and it will still be gargling rich and blowing all kinds of smoke.
2. The low end normally needs adjusting. To do this let it idle at around 1900 to 2000 rpm if it keeps dying it's probably too lean (which normally isn't the case from the factory). Once you've got it successfully idling at 2K or so let it sit and idle for about 20 or 30 seconds then try revving it up. If it sputters and has trouble revving up then it's too rich. Reduce the low end needle 1/8 turn at a time until you can go from idle to wide open without it sputtering.
3. Use synthetic fuel.
4. Be sure and use a fuel filter in front of the pump input.
5. Use after run oil (especially when you go to humid Nederland
). At the Nederland contest I didn't have any after run oil with me and I drove the plane home in my cool car then put it in the hot garage and forgot to put the after run oil in it. It then sat there for about four weeks without running. Next time I flew it died on the second flight. I pulled the engine apart and the back bearings were rusted BIG TIME (this was with about flight 60). After replacing the bearings it runs great again.
cd3217, try the things I've mentioned if you haven't already. From your initial description it sounded like it was just lean on the high end. After the engine starts breaking in you will get to a point where it starts leaning out on uplines. This will cause it to sag and not reach top RPM when trying to pull over the tops of loops or on verticals. To correct this all you need is to richen it one to three clicks. I think this is pretty typical as it breaks in. Another reason it may lean out on uplines is if the pump pressure is too low, but I find this doubtful since you never backed your pump off and it flew fine initially.
If none of this works then next thing I'd check is to see if you have rusted bearings. You can easily pop the pump off of the back and take a look at the bearings. Even though the engine is relatively new if the climate and shelf time are right the bearings could have rusted. Rusted bearings also results in the behavior you've described. If none of this works then perhaps you do have a clogged pump, however I'd check everything else first because that pump is pretty tricky to disassemble and pretty sensitive. If you do disassemble it do it on a CLEAN table.
One thing you may want to try before disassembling the pump is to pull the fuel line off of the carb and turn the engine over with a starter. If the pump is working you will see it pumping fuel out the tube that's normally hooked to the carb. This won't show you if there is a "slight" problem with the pump but it will let you know if there is a major problem with the pump.
Best of luck,
Keith