Freeing the cylinder on Medallion .049 w/ throttle ring

Jim Howell Sun Aug 11, 2019 3:31 pm

I have a Medallion .049 NIB dating circa 1975 +/-. It has a sliding circular exhaust restrictor and was originally intended for R/C use (why I bought it in the first place) but life got in the way and modeling took a back seat. Fast forward 40 years of storage in a drawer in an unheated/uncooled garage and I'd like to use it if possible on a 1/2A C/L stunt model. When I got the bug to try the 1/2A stunt, I remembered that I had acquired two of these engines and thought that they might be the answer for the latest C/L itch. But I also thought that one of them would be more effective if I could get the sliding exhaust ring off. When I tried to remove the cylinder, nothing moved when I applied pressure with the flat Cox engine wrench. By putting a drop of air tool oil in the intake, and putting an old TF Nylon prop up front, I was able to get the crank to turn over after a bit of gentle persuasion. But nothing else.

I thought about trying to heat something up with a Monocoat gun, but decided to come check out posts here that might apply. After reading a bunch of posts about problems with Medallions and cylinders, I'm about ready to drop this whole plan. Some of them talked about problems trying to get the piston back in the cylinder, some talked about getting burrs on the piston.

TIA for any insights,
Jim Howell

NEW222 Sun Aug 11, 2019 4:14 pm

Monokote heat gun would work. As well as using a plain old heat gun, or letting the engines soak in some fuel for a bit. Personally, I would go the soaking in fuel route first for a day and they should looesn up pretty good and then allow you to disassemble the engine to remove the throttle ring. Do not put these in an antifreeze bath, as bad things can and will happen to the plastic. I personally have not used my Monokote iron to do this before so cannot comment on how well it will work, but have read some have had good luck. All I ever use is heat gun, fuel bath, or crock pot with antifreeze, and lately, the fuel bath is my #1.

trebor3170 Tue Aug 13, 2019 2:07 pm

Be careful with the heat gun, it will get hot enough to deform or melt the plastic carb body Hot

. I did on a Tee Dee of mine, the carb body was cracked anyway, so that was one reason I was taking it apart.

Jim Howell Sat Aug 17, 2019 3:56 pm

NEW222 wrote:Monokote heat gun would work. As well as using a plain old heat gun, or letting the engines soak in some fuel for a bit. Personally, I would go the soaking in fuel route first for a day and they should looesn up pretty good and then allow you to disassemble the engine to remove the throttle ring. Do not put these in an antifreeze bath, as bad things can and will happen to the plastic. I personally have not used my Monokote iron to do this before so cannot comment on how well it will work, but have read some have had good luck. All I ever use is heat gun, fuel bath, or crock pot with antifreeze, and lately, the fuel bath is my #1.

I am pleased to be able to report SUCCESS!

Since I actually have two of the throttle-ringed .049's, I let both engines soak for 3 days. I took one of them to the workshop of one of my OFB's. While we couldn't get the cylinder to turn just with the Cox engine tools and hand pressure, we put just a little heat on the head, then rapped the tool lightly. Bingo! The cylinder turned and came right off. Although the exhaust restrictor ring was gummed up a bit on the base of the cylinder, I was able to use one tool on the glow head, and one tool on the slots in the restrictor ring. That did the trick. And, when we put the cylinder back on the case the exhaust ports lined up fore-and-aft. My OFB had flown a lot of 1/2A FF years ago using TeeDees. He got really excited saying that having them like that was worth a few extra RPM.

So, I came home and repeated what my OFB had done, and I now have two Medallions to use to scratch my current 1/2A C/L itch. Only negative I can see right now is that the second Medallion cylinder bottomed out with the exhaust ports lined up laterally, not fore-n-aft.

Thanks for the responses and recommendations.

getback Sun Aug 18, 2019 7:17 am

If it were me , i would run it and see how that goes before mounting to a plane / but i am sure you know this > what i am getting at is if there is goo built up in the crankshaft assy. you want get the rpms or can heat up . << Small Cox Logo

Jim Howell Sun Aug 18, 2019 8:09 am

getback wrote: If it were me , i would run it and see how that goes before mounting to a plane / but i am sure you know this > what i am getting at is if there is goo built up in the crankshaft assy. you want get the rpms or can heat up . <<

That sounds like a good plan. Thanks for reminding me.

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Freeing the cylinder on Medallion .049 w/ throttle ring

Freeing the cylinder on Medallion .049 w/ throttle ring

Re: Freeing the cylinder on Medallion .049 w/ throttle ring

Re: Freeing the cylinder on Medallion .049 w/ throttle ring

Re: Freeing the cylinder on Medallion .049 w/ throttle ring

Re: Freeing the cylinder on Medallion .049 w/ throttle ring

Re: Freeing the cylinder on Medallion .049 w/ throttle ring

Re: Freeing the cylinder on Medallion .049 w/ throttle ring