skaliwag

My Feedback: (1)

Have you thought about changing the carb on the ASP?

Mr Cox

There is nothing wrong with the stock carb on the .12 ASP. On the contrary it is a very nice twin needle carb. These are different from the air-bleed carbs, where the low end screw is really for the low end. On the twin needle ones the second needle adjust the whole midrange, so it needs to be set for that rather than the lowest idle.

The real issue though is the touchy needles, as with any engine this is indicative of an overloaded engine. The ASP is very happy on small props, and the largest load I've been able to use is the APC 7x4 but then I have to add an extra head shim (on 10% nitro). I have two engines where this has work well, but they are still much happier on smaller props, like the APC 6.3x4. They really need to do about +16500rpm on the ground to run well.

If you're using an MAS 8x3 then that is most likely the problem. Try a cox or rev-up 7x3.5 instead if you have some. That will give you a different kind of flying but for 8" props you'll need an Enya 09, or the ASP .15 (with blue head) for instance.

Here is a similar sized plane with the ASP .12 and an APC 7x4 prop (sorry for the poor quality, you don't see much...);

[youtube]http://www.youtube.com/watch?v=CppfZ0pF8Ms[/youtube]

buzzard bait

Thanks very much, I was wondering if a smaller prop would help. I'll give it a try and report back.

Jim

buzzard bait

I tried the Rev Up 7x3.5 today and it tached at about 17,500 rpm, but unfortunately the quirky throttling did not improve. On the stand, the engine at a high idle/low mid range will speed up some when I let it sit, then slow down and quit. It will run quite awhile at idle running around 4000. Pinch test at idle or at low mid range results in speed up and then it quits. High speed needle is set well and the engine is very steady in flight at full throttle.

Fortunately in flight I don't really have any trouble. I seem to be able to fly the plane around at low throttle just fine.

With the 7x3.5 the plane was louder, faster and harder to land. It might have had better vertical too, but it's hard to tell.

I went back to the 8x3 MA and like the lower sound better, and landing was good again. Vertical is certainly not lacking.

Still have no idea what's going on with the throttle. It's not a huge problem, but I don't really feel I can trust it the way I trust other engines.

Jim

Mr Cox

That's doesn't sound right, you might simply have a bad glow plug or something. Try a new one, I have used an OS#8 without any problems.
What fuel are you running?

Another thing to check is the spring in the carb, it should push the throttle barrel away from the high speed needle at all times.

It could possibly be an airleak under the carb, check the o-ring, and clamp bolt, for leaks.

buzzard bait

The fuel is S&W 10% nitro with synthetic plus about 3% castor. Works great in several other engines.

The carb spring is fine. I'll try another plug. Haven't checked for leaks...I'll give it a try later on.

Thanks,

Jim

Mr Cox

Fuel sounds fine, they are not picky on the oil, I have used anything from full castor to fully synthetic (for a full season) without any problems.

With 10% Nitro, and a large prop, I think you should try with one extra head shim though. This helps in my experience and that's what I use on both of my engines.

The engines are loud because there is no baffle in the muffler. The bolt spacing is common to most .10-.15 engines though, and you could try an OS LA muffler if you have one. Or the Enya quiete muffler etc.

longdan

I have an ASP .12 in a Pitts bipe with a cox grey 7.5 x 3.5 prop.
I also found the needles a bit touchy at first. I tried several different props - MA 8x4, 8x3, but found the 7.5x3.5 to work quite well.
Also a #8 plug, and 10% fuel.
Another thing I did, and I know its not right, but made it easier to tune, was to set the max throttle position at about 80% throttle opening. That last 20% hardly makes any difference to the engine rpms (maybe a few hundred rpm at most), but it makes it needle a lot easier. I wasn't worried about extracting every last drop of performance out of it. It still revs very nicely at 80% throttle.

BTW - the 80% is based on the computer radio settings. !00% is WOT, then dialled back to 80% on the readout.

buzzard bait

That's 2 votes for the OS no. 8 plug. I think I've got one to try.

I don't believe there's a head shim in the box, but I'll check. If I've got one I'll try it, otherwise, well, the engine does not really act over-compressed. Lighter prop loads did not really change anything but the top rpm.

Thanks guys, I'll keep at this and report back.

Jim

skaliwag

My Feedback: (1)

Does Nitro have a relationship with the venturi size (air volume) being sucked in?

buzzard bait

I think there's an air leak at the carb. I notice that it is hard to choke the engine with a finger over the intake...very poor draw. I will have to take off the carb, check the O ring, and replace or maybe clean up and put on some RTV.

I tried a new glow plug that I could not identify and it didn't help. Then tried an Enya #3, and that did help, but I'm still not getting a smooth throttle response.

Jim

Mr Cox

Check the draw-bar too. It is positioned below the o-ring and there can be leaks there.

buzzard bait

Yes, I had a minor crash and the carb got skewed, so obviously the draw bar was not really tight. That's what started me thinking that your carb leak idea might be correct.

Jim

buzzard bait

SUCCESS!! The draw-bar was not tight...good call.

The engine idles down a little below 4000 steadily for extended times, and it will throttle up quickly without quitting. Top end was 15,800 to 16,000 on the 8x3.

I do find the HS needle to be extremely sensitive. Only a click or two separates a good setting from a dead stick part way through the flight. I am guessing that this is because 8x3 prop is a bit too much load for this engine. Rather than going to a 7x4, I will try cutting 1/4 inch off the tips to make a 7 1/2 x 3 prop out of it.

But after carefully setting the needle I can now do touch and goes over and over with no worries. Thanks guys.

Jim

Mr Cox

Glad you found the problem, it is usually something simple too fix, but not always easy to find.

The main needle is a little sensitive on these engines, but you should at least have a few clicks to work with. You could try with reducing the compression, one or two extra head shims will help on larger props. I'm running with one extra for a 7x4 prop. It is a good exercice to tach an engine on different compression setting, same prop and fuel, there might only be 200rpm to gain but the ease of tuning can change a lot.

bps

My Feedback: (3)

I fly mine with an OS.10 on 15% and that is just the minimum power to fly with. The engine is the pet version so it has been around for a while but not much run time. Still difficult to believe this plane was discontinued! About all it needed to make it a truly great little plane was a decent covering job. Covering really stinks! I use Spectrum receiver, Hitec 81 on elevator and 55's on the rest. This is the third or fourth flying season. I am considering recovering and going to electric. I always fly till the motor stops and then glide to the 300 foot flying field. Have yet it miss with this great little bird.

buzzard bait

I've never tried making a head shim. What material and how to do?

Maybe a cooler plug would help. Also, I had 15% nitro this time; before I was using 10%. It's my impression the needle sensitivity is worse now, so maybe that's the reason.

Yes, the covering is pretty bad. I keep sealing up seams. But it always has some wrinkles and really does not look that good close up.

I have found that although I really liked the plane in the beginning, I am losing interest in it now even though the engine is behaving much better and the plane is flying very well. It's just not my style of flying. It's nice to be able to do some stunts close in, but I've discovered that I like really big maneuvers done as slowly as possible. I really like my LA 40 Racer, which has more pattern plane-like proportions.

Jim

Mr Cox

Higher nitro content advances the ignition, so yes, if the compression ratio is too high on 10% then using 15% will just make it worse.

The shims can be made from thin copper or brass sheets. Aluminium works too, and you can even use the aluminium from a soda-can. It is a little thin though so you might need more of them. These thin foils can be cut with a regular pair of scissors. The inner hole can be trimmed to final shape by using a dremmel and an appropriate sized stone. If you use material from a soda-can, then remove the paint with fine emery cloth.

Regarding flying style, I don't like 8x3 props, they are only good for prop-hanging. Try a 7x4 or 6.5x4 and let it rip instead.

buzzard bait

I've experimented with props a lot. I love low pitch/high diameter. I don't do "prop hanging".

Jim

buzzard bait

I cut the MA 8x3 down to 7.5x3 and got 17,400 rpm on the ground. Very steady, awesome power for this plane, but the needle is still sensitive and the throttle is not as reliable as the ones on my older OS and Enya engines of similar size. I haven't done the head shim, but I think I've seen enough of this engine now to know that it doesn't suit me. The engine might yet do better with more experimenting, but I'm done with it now.

I do appreciate the help I've gotten here. Thanks guys,

Jim

Mr Cox

Don't give up on it, I have two engines and they both run better with an extra head-shim on the larger props. You can also put a smaller prop on it (6x4-6x5) and use for something speedier than the extra.

buzzard bait

I have an ASP .91 that I was about to ditch until I bought a head shim for it and it's been a terrific engine ever since. So I suppose a shim could do the trick on this little one too. It's just that I have good options with the small engine, whereas the large one would have been hard to replace. I'll see. Thanks.

Jim

Digger-RCU

I know this is gonna sound strange, but i still fly mine on the Norvel 074. It is no speed demon, but it goes where I point it, and has always been fun to fly. I have had mine for 6 years, although I have not flown it for the last three as I was in Okinawa.

Digger

buzzard bait

I can understand that, Digger. The plane is so light, you can enjoy it on low power in a small space.

I'm flying mine on an Enya .09 now. Much less power than the ASP .12, but I can throttle it up and down with no fear of a dead stick. It's worth the power loss.

Jim

Mr Cox

With the risk of sounding like a broken record (if anyone remember those...), all the ASP engine needs is a lower compression setting and it will run like a champ.