I own a Big Mig .049 Revlite version. Its just not living up to what I expected of it. I've owned the engine for 2 years and it just never seems to work consistently. I feel the pinch up top is too tight. The engine is a bit hard to start but then its all over throughout the flight. Has anyone ever tried to lap one of these style engine in. I'm convinced the fit is tight causing overheating. The engine starts to sag especially in the maneuvers. I was using a trimmed down 5x3 cox prop which surely isn't overloading the engine. I was using 10% fuel and also 35% fuels. I tried additional head gaskets thinking it may have been overcompressed as well. This just complicated starting the engine. The pinch is really harsh cold or hot . I believe the engine has about 1.5 honest hours on it. It just seems as though its not making the power like it should. I have earlier ABN versions which run 3-5 k over this one. This is the first Revlite version I owned. Initially, I filled the cylinder per instructions with castor for 24 hrs etc. I ran it in small 2 min intervals and followed the typical procedures. I'm about spent on this one. I exhausted several hours on this engine today and this is the only logical explanation I have. I switched to a APC 5.5 x2.5 on the ground it was reading 18K. On another engine same type we were seeing 23k with the same prop. That's a huge difference and mine won't even hold the 18 consistently. I would say I'm making almost Black Widow power with a bit more steadiness. This isn't all that impressive. I was wondering if any of you ever had experienced this. Ken

Ken,

I have had success with 8 of these engines over the past several years for the several 1/2A multi-engine profile scale airplanes I have built and experience with about that many more with the engines others have used for these events.

I have had no problem with the way these engines run.  (I should mention that they all have been Big Mig versions, not the AME versions.)  Each one has had a break-in period of at least 50 minutes to 1 hour on the same fuel I intend to fly with them.

Yes, these things, out of the box, are extremely tight at TDC and are hard to hand start at first.  One thing I do and I do not believer it hurts anything  --  When I get ready to start the break-in period with the engine on a test stand hooked up to its fuel supply, I remove the Glow plug/head, put a couple of drops oil on top of the piston, then apply an electric starter, turning it over really fast by the starter in intervals of about 5 seconds.   It is remarkable the amount of fuel you will see these things pump past the piston.  You will see a significant spray coming out of the top of the cylinder.  I do not think any harm is being done as it is obvious there is plenty of lubrication for the crank shaft as well as the piston/cylinder.  I do this for about 5 or 6 spurts of 5 or 6 seconds each.  Then, put the plug on, it should start right up with the starter.  Run a total of at least 50 minute, the instruction's recommend 1 hour.  It should be easier to start, in fact hand starting is possible.

The enginewill still be tight at TDC but not like it is when you take a new one out of the box.

I have some Novel AME engines, but have not yet run them.  Apparently, these run better (as in more consistent) with some form of pressure.

Keith

..The engine starts to sag especially in the maneuvers.
..The pinch is really harsh cold or hot.
..I believe the engine has about 1.5 honest hours on it.
..I ran it in small 2 min intervals and followed the typical procedures.
Ken

If you bench-run it, when it starts to sag, feel the crankcase beneath the crankshaft. If it is binding, it may feel hotter than normal.
Lots of pinch usually means it is not broken-in yet. Perhaps with the extra fiddling, you may not have as much run time as you think.
Two minute intervals is not necessary. The Revlite cylinder is hard-anodized aluminum oxide coating on an aluminum cylinder, and the piston is high silicon aluminum...neither need heat cycles.
If the crank does not need polishing and the cylinder has no scoring, I think you may just need to give it more run time until it settles down.

Good luck with it.
George

I wouldn't expect a noticable bind.  The only way I know to check crank fit is to manually spin it in the case with both clean and dry.  It will be smooth, but stop quickly if too tight.  It will spin several times when it is right.  A friend has an AP Wasp that would burn a plug every flight.  Felt fine when turned by hand, but when disassembled, the crank was tight by the above test.  I polished it down as outlined, and we have a VERY happy motor now.