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-   -   OS Max .50 Helicopter Engine (http://www.rcuniverse.com/forum/glow-engines-114/5655219-os-max-50-helicopter-engine.html)

jbloom 04-02-2007 05:40 PM

OS Max .50 Helicopter Engine
 
1 Attachment(s)
I aquired an old Miniature Aircraft Kit 1000, distributed in the mid 80's. With it came an OS Max .50 engine. That engine has now quit. From the looks of it, it only needs a piston, ring, and head shim. But the only thing I can find is an OS Max .50 SX at Tower Hobbies. I called them and the technical department says the parts for the 50 SX will not work on the engine I have. The specs say the piston is 22mm in diameter. As best I can tell with a metric ruler, so is the one I have that needs replacing. I'd much rather spend $65.00 getting the parts to repair my engine, even though it is old, than to spend $200.00 + to get a new one. Can anyone validate the information I got? Are the parts from the 50 SX really not interchangeable with the older 50 that I have? Here are some pics of what I have. There are no other identifiers on this engine other than OS Max 50. The carb is a 5B, and on the backplate is "5107". Other than those, there are no other markings.


w8ye 04-02-2007 06:39 PM

RE: OS Max .50 Helicopter Engine
 
Contact this guy and send him the engine. He will fix everything wrong with it or sell you the parts to fix it?

Frank C Bowman
1211 N Allen Ave
Farmington, NM 87401-3568
505-327-0696

frankbowman@mylifeline.net

I doubt if any parts are compatable between the 50 FSR and the 50 SX

downunder 04-02-2007 07:33 PM

RE: OS Max .50 Helicopter Engine
 
I don't know if it's my imagination or the camera angle or what but something doesn't look right with the liner. It seems to be turned way out of line judging by what seem to be the port heights. Have you ever run the engine or just couldn't get it to start when you bought it?

w8ye 04-02-2007 07:52 PM

RE: OS Max .50 Helicopter Engine
 
The engine appears to be a OS 50 FSR

Here is a location of an original parts list http://www.osengines.com/parts/xr15119.html

Parts list for the carb http://www.osengines.com/parts/xr25181009.html

jbloom 04-02-2007 08:26 PM

RE: OS Max .50 Helicopter Engine
 

Quote:

ORIGINAL: downunder

I don't know if it's my imagination or the camera angle or what but something doesn't look right with the liner. It seems to be turned way out of line judging by what seem to be the port heights. Have you ever run the engine or just couldn't get it to start when you bought it?
haha.. good catch, I just quickly put the parts back together to take the picture. I never thought to check the liner.

w8ye 04-02-2007 09:43 PM

RE: OS Max .50 Helicopter Engine
 
What should be the rear of the liner is positioned into the center of the exhaust port

DarZeelon 04-03-2007 12:54 AM

RE: OS Max .50 Helicopter Engine
 
Mr. Bloom,


Please make sure the sleeve is rotated so the large port is aligned with the exhaust port in the crankcase...

Of the four ports in the sleeve, the exhaust is the largest and the tallest (it could be bridged).

The boost port is the smallest and is flanked on both sides by the two Scnürle ports, angled away from the exhaust.
You cannot go wrong with this and there is only one way it would fit.

To do this you will have pull the sleeve up and out of the block, and to remove the back-plate.

Then, you will need to make sure the piston ring gap is aligned with the pin in ring-groove in the piston.
This pin prevents the ring from turning and catching in one of the sleeve's ports (it keeps the gap aligned with a 'vacant' area of the sleeve).

After making sure the piston and ring are correctly aligned, you will have to insert the sleeve into the crankcase, with the ports pre-aligned (you will not be able to rotate it afterward) and to use a finger through the back of the engine, to make sure the piston and ring slide smoothly into it.

The sleeve has a taper at the bottom to facilitate re-assembly, by compressing the ring into its groove, as the sleeve is pushed down onto the piston.


Failure to align the ring gap with the 'anti-rotation' pin, or rotating the sleeve after it is over the piston, will result in you having to buy a good supply of rings from Frank Bowman...

These old FSR engines lasted a life-time... If you assemble it properly, your grand-kids will likely be able to inherit it from you, in usable condition...

Bax 04-03-2007 10:29 AM

RE: OS Max .50 Helicopter Engine
 
The engine shown in the pics is an O.S. Max .50 FSR-H. Parts for the current O.S. Max .50 SX-H will not work in it. The dimensions that count, such as liner O.D. and positioning in the case would be different from those in the .50 FSR-H. Parts for the old .50 FSR-H are no longer available from us, or from O.S., in Japan. The engine has been out of production for too long.

jbloom 04-03-2007 06:41 PM

RE: OS Max .50 Helicopter Engine
 
Thanks a million for all the responses. I had hoped that the .50 SX piston would work. I wasn't going to replace the sleeve, it looks pretty good. But it appears finding parts is going to be the problem. You would think that a .50 in 1978 is still a .50 today. but I suppose there are more considerations than just the diameter of the piston. Such as it's length, size of the pin that holds it to the connecting rod, etc.

I'll be in contact with Mr. Bowman.

w8ye 04-03-2007 06:58 PM

RE: OS Max .50 Helicopter Engine
 
Call Frank Bowman. He can make the parts for you or repair the old ones? He is well known for makng rings for all kinds of model engines.

jbloom 04-04-2007 06:23 PM

RE: OS Max .50 Helicopter Engine
 
Thanks! Mr. Bowman and I have talked. Unfortunately, he doesn't have a piston, and I must have one. I have however found someone who has an engine in excellent shape (at least based on the photos) that I can pick up. So it looks like that's the way I'll go. Then put some bucks back and get ready for a new engine at some point. Or maybe just a new chopper with a new engine.. :)


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