OS Max 40 FSR

Can anyone provide advice on running the old OS Max 40 FSR for stunt? Suggestions on prop, venturi diameter, fuel, run style, etc. will be appreciated.

Also, I have heard the rings are a weak point and need replacement often. Any experiences on this?

Thanks for your help!
David

David.......I know that they respond best to a flat prop.....11X4 apc or, better, 11 1/2 X 4 APC.... run in a lean 4 cycle....

See Ya

Check with Paul Walker. IIRC, he used OS 40FP pistons and liners in his FSR cases with great success. The parts drop right in and eliminate the nasty OS rings - which break early and often.

Then grab some flat pitch props like Rich mentioned and enjoy.

Ron King

Seems the ring problem requires Frank Bowman's touch!
Bill <><

Bill:

Yes - after posting the original question I thought of the same. Figured I would get a couple of the Frank Bowman rings for the 40 FSR to have them in reserve. I wonder if the ring problem was caused by the quality of the ring itself or something inherent in the engine? I suspect the former (i.e. ring quality) as I cannot think of anything in the design of the engine that would wear/break rings. Comments?

Also, thanks to the others for their comments to get me on the right path.

Regards...
David

David,
Pretty sure it's just the quality of the ring.
There were quite a few guys using these in the '80s. Paul W., Bob Hunt (IIRC), and others. High rpm/low pitch from what I remember like Rich P. said.
I never had one myself. Went from the ST 46, etc., right to the pipe.
Bill <><

Not long ago, NW Skyraiders own John Hall and I were talking about Mike Havenick (since he hasn't been seen lately). Mike had bought one of John's OS .40 FSR's for a Brodak Cardinal. John said the .40FSR is a real strong runner. He controlled the power with a small venturi, .250" or less, as I recall, an extra headgasket, 5% pop and a 12-5 RevUp. I would certainly look for ABC conversion parts, or a complete engine.

A NIB OS .40FSR ABC sold Saturday at our Swap for $60. Also, considering that the FSR was copied to make all the Royal, Thunder Tiger, Magnum, Tiger Sharks, ASP's, etc., anything that works on those should work on the OS.

As for putting in the FP P&L, PW says it is more complex than "drop in". The cylinder doesn't align correctly, so the wristpin pads have nothing to keep the pin from working out. The pads were removed and clips fitted into grooves cut in the piston. However, if the .40FP parts would fit, so would Tower .40, and maybe .40LA. With no boost port in the .40LA sleeve, that might be interesting. Might also be able to bore the case and put a .46LA P&L in it, or even the Magnum XL .53 P&L. Steve

LAST EDITED ON Dec-12-04 AT 09:57 PM (CST)
 
">Can anyone provide advice on running the old OS Max 40 FSR
>for stunt? Suggestions on prop, venturi diameter, fuel, run
>style, etc. will be appreciated.
>
>Also, I have heard the rings are a weak point and need
>replacement often. Any experiences on this?
>
>Thanks for your help!
>David "

HI David

This is a good engine if it is a FSR-S , This one is the best of the 2, The FSR had a crankshaft with much more timing, The rings I didn't have much troubl out of, and There is also a ABN lapped piston and sleeve,
The OS FP piston and sleeves DO NOT drop in and work, It takes special machining of the piston to put cir clips to hold a pin in place, if you use the FP pin it will just run into the port and seize the engine.
You may can find an Old Magnum or Royal P\S that will work in it though, plus there are still OS parts for that engine around, I have many of them.

Regards

Randy

PS you can tell if it is a FSR-S it will have the S stamped on teh counterweight of the crankshaft

Very helpful information! Thanks everyone.

David

I have 1 OS Max 40 FSR and 4 OS Max 25 FSR's. These engine are much more powerful than the LA or FP engines. My OS Max 40 FSR will turn a 12x6 prop and the OS Max 25 FSR will turn a 10x6 prop. I replaced the RC carburator with a venturi. Hole diameter of my venturi is the same area as the hole in the RC carburator plus an area increase of 10%. I am using 15% nitro 16% oil fuel with enough caster oil added to change the fuel to 12% nitro 30% oil. The engines run great. I have never looked to see if the pistons have rings. If they all have rings I am not having any trouble with them. My engines run great with or without a muffler. The 6 pitch prop is too fast for stunt. I have been using a 4 pitch and it seems a little bit fast.

Gary Weaver

>Can anyone provide advice on running the old OS Max 40 FSR
>for stunt? Suggestions on prop, venturi diameter, fuel, run
>style, etc. will be appreciated.
>
>Also, I have heard the rings are a weak point and need
>replacement often. Any experiences on this?
>
>Thanks for your help!
>David