Originally Posted by Glow-man

I bought two sleeve at Towerhobbies. At that time I could get just the sleeve for 75$US. For some reason they sell the sleeve and piston for the 75AX. If you still want that engine, just get it. I own 2 55AX, 2 95AX and one 120AX. I do not know exactly why the 95s started to give me problems, but I did all the tricks talked about above and it would dead stick on me, but seemed to run great on the ground and have compression. Actually now that I think about it. I would use OS 7 glow plugs. I still do on one of them. What it does is smooth the engine at low rpm. The AX family have a tendency to vibrate at low to middle rpm. Anyway what I noticed, is when I installed a new glow plug, I would get about 3 flights before starting to flame out. When it did flame out I could see the prop windmill. It would loose all compression. I was an expert at dead sticks. That summer I landed about 10 dead stick with my T 28 with bent fix gear at its worst. What I have notice is my engine would destroy my glow plug element. It was visible to the eye. That is when I really realized it had nothing to do with adjusting my carb, shimming the head or what ever trick I was told. It is possible I may have over heated my engine at one point before all this started because I did not properly air cool them. That was when I was trying to keep the cowl scale. However they did not show signs of failing till later. I know it sucks to put more money on what should last longer. In my case I love those engines. They run like a clock. When I go fly at the field I do not have time to fool around with stuff. It has to be start and go. I am a busy family man. Except for that event I just talked about. The OS AX family engines have gave reliable fun.
Oooyaaa! Next thing is after I changed the piston sleeves I always used the stock exhaust. Simply because perhaps using other types of after market brands might have cause my problems. I cannot say for sure. Below is an old video of my Spitfire with a new OS 95AX at the time with custom exhaust. Enjoy the story.
https://youtu.be/AdtwBGbmceQ

Originally Posted by Glow-man

I did not read all your thread and did not read how your problem started. I own 2 OS 95AX since 2009. Both run every summer. To keep it short, I had to change the piston sleeve. My engine would flame out once in the air. Trust me I have tried everything first. That occurred in 2012. Since I have replaced the sleeve on both engine they have been great to me. Strange this happen 3 years after I bought them.

Originally Posted by David Ford

Al,
You might want to take Cougar's offer to look at your engine. I would offer but I am on my way to the US nationals for a few weeks to compete.
Your tests and observations suggest something is going on in the engine. OS says the main needle s/b 2 1/2 turns out, so 3 is still in the ballpark so the engine should run and be some rich, yours seems lean like there is too much load or has a fuel restriction. The black carbon on the piston won't normally be there if it is running rich, that is a sign of lean/high load.
Cougar suggested some reasons for the black, like a bad bearing, all sorts of things like that could cause the black and also make the engine run hot/lean trying to overcome the drag in the engine.
Cougar's suggestion of a second set of eyes is a good one.

Best of luck Al

Originally Posted by Cougar429

Believe it or not that is not all that dark. There is just a LOT of it.



I have only seen this type of deposit amount on a few make engines; different names, but from reports all coming out the same factory door. Their fit was so poor air leaked in through the rather narrow front bearing and would continue to idle even with the throttle completely closed.

I have also seen this when the needles are so far out of whack the lube comes out the exhaust in visible drops and a smoke cloud you could hide a DDay invasion force behind. It may be worth it to go back and check they are at least close to recommended and or have someone else have a boo. Believe me, over the years I have seen many times where staring at a problem till my focus would blur would not find a resolution, where another set of eyes could see it in seconds. The reverse has also been true.

Generally OS is not known for this and their carbs are excellent. That being said, if there is an air leak you may need to set it this rich to compensate. A few suspects, especially after long-term storage, would be the carb base O-ring that seals it to the case, rear cover seal and even a loose head or plug.

There is the typically difficult to find HS needle O-ring, but that generally leads to lean mixture.

All these are moot if the engine is in poor mechanical condition. The most critical fit is between the crank and case, (where the aforementioned engines would suffer from poor QC). This can be made worse on any engine by running a bad set of bearings, poorly balanced prop and using the engine after a "Goat" with a bent crank.

You're not that far away so could offer to have a look and try and set it up on the test stand, though may be easier to find someone local.