The ASP/Magnum .91 sereis 3 runs just like the OS .91FX. You would be saving yourself a boat load of money.

Aren't you a self proclaimed Mechanical Engineer?

http://www.rcuniverse.com/forum/m_90...tm.htm#9036815

Post number 37


I think the technical term is guru...

"Motorman37" I actually have to come clean and state that I actually have a 2 year Degree in Mechanical Design and do not have a 4 year Degree. My post's might jump around a little once in while, that is my adult ADHD acting up.

That's OK...

Not self proclaimed. The university I attended proclaimed that I am a mechanical engineer.

Edit: oops, sorry I see you were replying to motorman.... ( but I still have a BSME)

Same Here.

same here

Yes!

There may be a little where the ring gap is, but shouldn't be a whole "patch"

You might try to take the piston out, and clean the groove that the ring rides in. Sometimes if dirt or carbon builds up in ring, it can allow for blowby. I.e. loss of compression.


If you had an airleak like was suggested, you'd know it. Shimming the head would not fix the problem of overheating due to an airleak.
I'd clean the ring groove really well, put it back together with the ring gap in a different location, and try it again.

You should also be able to look at your head shims to see if gas is getting past them. You'll know it when you see it. I'd put my money leakage past the ring, before I put it on a "warped piston"

How hard can this be? There`s one ring, one liner, one head and one piston. The pressure is leaking past one of them, use soapy water, oil etc and look and whatch for the bubbles.

Looking at the head shims, they are absolutely clean. So.... I'm putting my money on a warped cyclinder. The ring is still free to move in the groove, ie not built up with goo yet. (heck its only 2 gallons old).

I would move the ring gap like someone mentiond but the ST ring will only fit two ways, and changing the it from one to the other would only rotate the ring about 5 or 10 degrees leaving the dark patch of the cyclinder still in the same region of the ring it was in before. (the dark patch covers almost 1/4 of the cyclinder from about 9:30 to 11:30 as you look down on it)


Thanks, (if anyone is interested, I can try to take a picture of it tonight... just let me know so I can plan my night.... Vikings Packers game tonight ya know!)

never seen a "warped piston".................

The idea of the warped piston comes from Hobby Services on return of an extremely overheated OS 1.60. You will have to read the threads to find it though.

http://www.rcuniverse.com/forum/m_24...tm.htm#2470750

I have a G75 ST and it seems like it needs to be shimmed slightly. I phoned tigre engines in the UK and he said that it was too much nitro. I was using 10% Supaglow then moved to 5% it improved but still not right even with a cool firepower plug. So I ordered the Super Tigre cool plug and a gasket for the head to add on. Also went to my local club where I seen another engine the same having the same trouble that engines bearings let go. But I was wondering if you guys could tell me where to get the shims from as tigre engines said the don't do them just the head gasket.

With lower nitro fuels, you don't use a "cool" plug. The O.S. #8 or the #6 plugs are good "all-around" plugs to use. A "cool" or "cold" plug is for high-RPM/high-nitro operation.

Head Gasket = Shim

On the Super Tiger they are one and the same

How about just a stuck/broken ring?

Paul

http://www.youtube.com/watch?v=kBHVuquATDM

This is very much the same but not as bad as the engine shown in the video. It just does it when throttling down to idle speed then wears off even if I set it richer than what is good for flying with. I had a carb problem also too rich in the middle so changed it for an Italian ST V60 carb. Very nice also reduced it but not completely. And when I run it ,it was positioned on it's side. I plan to use it in an inverted position now in another plane a Graupner Extra 300S 63" span. I have a feeling this will induce it. Paul the piston ring I checked and it nice and free no castor build up or any carbon on it or around it also using Model technics Supaglow fuel was thinking I might go for some straight fuel see how that goes what do you guys think. Reading back on this forum I read that one of you guy's are having problems getting rpm out of the same engine. It must be a major fault because mine even with the timing issue it turns a 12x8 with ease Graupner G sonic. Any further help on shimming or general improvement methods are more than welcome.