Hello all!
About 8 years ago I built a GB 300 and installed an ASP .91.... I had few problems with my trainer plane and os FP 40, but could never really get that ASP to run right Sometimes it would start right up and other times I could spin it for hours with no pop. Flameouts were a contant problem and I was always adjusting the mixtures. I got so fed up that I quite flying planes for 8 years and took up helis instead, "Without one flameout in a heli for the entire 8 years".

Recently I have been reading up on the bigger 40% planes. I would love to do one some day, but realize that I need more practice. I have that 1/4 scale extra 300 that could get my skills in shape, so I broke it out this weekend and proceeded to tinker with that engine again. All those bad memories came right back. This piece of junk is a nightmare and runs even worse now. I can get it to run, "sometimes" but it dies about 5 to 8 seconds after removing the glow starter. It does this both at idle, midrange and full bore. I would think that would indicate a rich condition, but it doesn't sputter and the problem continues with both rich and lean needle settings. I see no air bubbles and tried new plugs. As this engine was always a problem, I'm tempted to just junk it. Any advice here from the experts? Are large engines harder to run than the .40 size? I really hate this engine. By the way, I also dug out and ran the old OS fp 40, and guess what. After sitting for 8 years, it started first try and purred right along.

Searching the net for a replacement engine gave few results. It seems that there is just not many making a .90 size engine any more. Os has one but I want to get this plane in the air as cheaply as possible as I just consider it a temporary large trainer. I also found a .91 magnum but I think that is really just an ASP which I will never buy again. What do yu guys think about putting a .61 in a goldberg extra. There are alot of good cheap .61's around but that .91 was a thrill when I could keep it running and I would hate to give up that much power. All thoughts on all of this will be greatly appreciated.

Your correct in saying that ASP and Magnum are one and the same.

Sorry to hear about your old ASP 91. I have an old 1.08 and seems to run just fine. There was a problem with them having too much compression for using very much nitro in the fuel.

The ASP/Magnum company has a new .91 out now that looks like an OS 91fx. They are on sale right now from Hobby people as Magnum XLS.91 I think. Look in the ads.

Good luck,

Jim

I just got one and it is not a beginner's engine. The engine requires low nitro and lots of patience to get it dialed in correctly. Not a very forgiving or user friendly engine, however, I do like mine a lot since it has a lot of personality and is now very reliable and always hand starts.

My ASP .91 runs fine one FAI (0%) fuel and 5% nitro. But with 10% it detonates, runs hot, and quit once, if not running a much richer setting. With 5% and less it is very user friendly except setting the idle is a bit tough with FAI fuel. With 15% or higher I wouldn't be surprised if it would act as you describe. You may have damaged it from running high nitro fuel.

I and other's in my club used a lot ASP's about ten years ago, it seemed like they had a quality problem with the carbs back then. We had the same problems as you described, a new carb would usually fix the problem.

Just a wild thought here, Maybe you can find a comparable OS carb to to fit in your ASP 91? I'll bet you a million that the stock carb is to blame for your troubles.

If you just want to get a new one for cheap, occasionally you can scan the RCU for sale ads, and find some great deals on used 4 strokers. Thunder Tiger also has a four stroke line, I have been surprised with their quality, and user friendliness, The TT 91 would be a good choice. Magnum also has a 91, maybe its too similar to your ASP, But 8 years later, They probably fixed the problem you have had, and are running great now??? Anyway, worth a try, you would still have a new warranty, and if You hate it too, send it back!
Two strokes are another option for your CG Extra, I think the ASP 108 would be good, Very powerful for your plane, would give you great Vertical. Or Super Tiger's 91, its a cheap engine, and pretty powerful too.. And then Thunder Tiger may make a 91 two stroke, I cant remeber, but its worth a look.

There are lots of cheap alternatives, Search around, You'll find one you like. And remember, You'll have a Warranty..

Hope this helps, Coulter

The ASP 91 and 1.08 had the same carb. Actually it was a very good carb, but a bit oversized for the 91. In fact I like it better than the OS carb because you don't have to use a screwdriver to adjust the low speed needle. Another possible problem is muffler pressure, it needs lots! I have a pump on mine because the carb is slightly above the tank, but the fuel draw is less than ideal without good muffler pressure. If not using the original muffler then this could be the problem.