Sportsman cylinder wanted...yep, another one!

The sportsman and Olympic pistons won’t work in the wrist pin version .15 cylinders. The fit is way loose.

So I guess the best bet is to grab the whole assy. Thanks Jason

Medallion .15 cylinder thread does not match the other .15 engines!

Every .15 cylinder is interchangeable within the TD, Olympic, Sportman. I really can’t see why they would have a special thread for the Medallion that shares the same case.

I don’t have a .15 Medallion but I do have .09’s in TD and Medallion and they share the same case and cylinder threads.

Hi guys, thanks for all the info. I tried a thick-wall .15 Medallion wrist-pin cylinder on the Sportsman, and the thread was too big. Took me by surprise too, till then I thought all .15 cylinders had the same thread, but it obviously 'ain't so, Joe' ! I've already got a tatty user with an Olympic top-end so I want to keep the latest find standard, hence the search for a single bypass cylinder. Probably gonna take a while, but that's cool. Plenty of other toys to play with in the meantime  

Cheers guys,   Rob

Just checked my Cox .15 engines and lo and behold, the thin walled TD cylinder with dual intake ports have a smaller diameter threaded portion like the Sportsman. So it is safe to say Cox enlarged the crankcase on the later models. Find an earlier thin wall cylinder and it will fit. Can't post pictures right now but will try if need be.

gkamysz wrote:Medallion .15 cylinder thread does not match the other .15 engines!

I ran into this recently, I had a Medallion crankcase assembly that needed a cyl. Bought a Medallion cyl. from Cox Int. from their last parts find and it would not screw into the crankcase. Threads were different.
Also got a .15 muffler that won't work, won't pass bottom of cyl. I still haven't figured out why.

I have a Medallion .15 and a Sportsman. The Medallion has 13/16" threads and the Sportsman 3/4". I suspect later TD.15 MKII Special also has the larger thread.

A short while later.....

I have a 3 transfer .15 cylinder I had to dig out. It does have the larger thread. Heh, I forgot I had a ~20 Medallion .15 piston/cylinder sets, but they are all 13/16.

Well I’ll be darned. Good info, I had no idea.

Howz this for a theory... ...the 1961 TD.15 used the same cylinder as the Olympic (and Sportsman, minus a bypass flute) with a 3/4"-32 thread. When the cylinders cracked at the ports, a fix was needed. The Special .15 came out in '62 with thicker cylinder walls and a larger 13/16"-32 threaded neck, and if the info on M-H Tools site is right, that's the same year the Medallion .15 hit the market too, so of course it would have the larger-threaded Special .15 c'case.
  Nice theory, I think, makes sense--doesn't mean it's right, though..anybody gotta better one?
                So, does anyone actually own a thin-wall Medallion .15 that they bought new in 1961??

That's very reasonable.

Hi folks,  just to let y'all know I finally found one of these. The engine now looks great, runs fine and has found a new home. I got offered a NIB Sportsman at a good price, too ...been a good week, except for missing out on that yellow Strato Bug on feebay --so still after one of those. Anybody got a rough one they're sick of looking at???

Glad to hear your on a roll. The real deal pickle is up for grabs on ebay a MK II looks mint.
No doubt the cream of the crop for Cox TD style engines.

https://www.ebay.com/itm/Excellent-1965-Cox-Mark-II-Special-15-C-L-F-F-Model-Airplane-Engine/153636736423?hash=item23c5768da7:g:jAAAAOSwqf1dbW6e

Yep she's a beauty all right, but so's my one--watching this one tho, keen to see what it sells for. The only gap in my Cox collection now is a Strato, been looking for ages and missed out on two already. Should have got that yellow one just sold on ebay, stayed up all night to be on at the end, finger poised and twitching...sold for only just over my max ...next time