Cylinder Question

I did that just an hour ago while rebuilding a BW. I got a magnifying glass under a 500W lamp and could see a slight bur on the upper side of the exhaust port. I ran the back side of an exacto blade lightly across it and got it smoothed out. I could have used the other tool, but I was lazy and the exhaust slot tool is easier. Not again. The last time I pushed the piston in it was still a little tight and then it smoothed out. Feels normal now. Just don't scratch the chrome off.

EXModelEngines wrote:Sometimes with the older engines that have the large exhaust port the wrench will leave small burrs on the inside edges of the ports.

I would try a little extra fine steel wool on the inside around this area. I have also had success using a small file, but it is tricky sometimes, as you do not want to ruin the cylinder.

Regards, Matt

Cox cylinders are fairly soft free machining steel (12L14 or similar?) burrs can be easily removed with an Xacto knife.
Al
P.S. One year back in the 70’s Cox was pushing their Bush Master plane. A relative of mine was a Mgr in a major department store chain. They sold hundreds of Bush Masters at Christmas and soon after Christmas got a lot of them back as returns. A good many of the engines had burrs inside the exhaust ports. Obviously a screwdriver had been poked thru the exhaust ports (probably while trying to remove the glow head). It was easy to remove the burr and the engine was as good as new. (Actually it WAS new!). I think I may still have a few of that batch.
Al

Thanks Al,

The exacto trick never occurred to me. I've got several old swap-meet engines with this cylinder damage, and didn't try to correct them for the reasons given by Mark. Well, they're laying there, not doing any good, so might as well give it a shot!

Kim

Thanks everyone! Wonder what I did to do that.

Ah, what the "ham-handed" can to to a perfectly good cox! Just think how many have been "tossed" for that very reason.

microflitedude wrote:I have an older .049 piston that is hard fitting in the cylinder. I took my BW cylinder off, and when I tried to put it back on, it too was hard. Are they burred somewhere? I remove them by the fins, not the exhaust ports...

Thanks in advance, Matthew

Matthew,
Since you indicate that you used the fins and not the exhaust port, I would guess that either you may have put a slight warp in the cylinder if it was extremely hard to get loose, or if the engines were well worn, the piston/cylinder wear may be out of round.

I would first try turning the piston to different positions and trying gently to insert it into the cylinder. You may find a spot where it fits easier.

George

I jumped in and posted, having missed where you said you used the fin tool. I don't know what else could have happened. Maybe George got it right.

gcb wrote:

microflitedude wrote:I have an older .049 piston that is hard fitting in the cylinder. I took my BW cylinder off, and when I tried to put it back on, it too was hard. Are they burred somewhere? I remove them by the fins, not the exhaust ports...

Thanks in advance, Matthew

Matthew,
Since you indicate that you used the fins and not the exhaust port, I would guess that either you may have put a slight warp in the cylinder if it was extremely hard to get loose, or if the engines were well worn, the piston/cylinder wear may be out of round.

I would first try turning the piston to different positions and trying gently to insert it into the cylinder. You may find a spot where it fits easier.

George

Now I remember the other other motor I removed from the ports as it didn't have oval head. The black widow was never really over tightened I don't think. How tight do they need to be?

Nothing. Still isn't free. Will it wear off on it's own?

microflitedude wrote:Nothing. Still isn't free. Will it wear off on it's own?

Maybe a mineral bath could do good it sure wouldn't hurt to try and could disslodge any loosely attached debris.

Or a sonic cleaner If you have one.