I just acquired an OS 35 and am wondering how much more power this motor puts out in relation to a fox 35. Reason being: Looking for a decent kit ..profile....to put it in...Im not looking for blazing speed, just sport flying. All Ive ever flown were fox 35s..thanx in advance....Bob

Which OS .35? The newer FP, or the classic Max S?

The FP may require some rework to tame it, the Max is a great classic engine pretty much as-is! Would go for a little smaller "classic" styled airplane for the Max, profile Nobler or the like.


W.

I'm flying one on a Primary Force at about 5000', has plenty of power. APC 10.5x4 prop, Powermaster GMA 10/29, Fox RC Long plug, tongue muffler. Another guy in our club runs one in an ARF Nobler, flies great. Like the Fox, 25% oil or better is a good idea.

cheers,
Ken

I saw Bill fly this package years ago...wonderful stunt pattern, with a very nice motor run!  One of the most impressive flights I've seen, even with the "old" OS 35-S!

Bill, funny thing is we spent two seasons after that trying to get our OS 35-s to run as well as yours did...with no success!  Guess everyone can make a 35-s run well except me...

Bob
I've come to the same conclusion about profiles and the older motors...   Didn't have vibration problems with the Foxes till I built a Skyray with a real stiff front end...   Shook like H***...  But the old skyray that I put together out of the box in two days for Skyray Triathalon at Sig runs smooooth with any old Fox....      
Ain't old motors great!!!
Later
Jim

I just acquired an OS 35 and am wondering how much more power this motor puts out in relation to a fox 35. Reason being: Looking for a decent kit ..profile....to put it in...Im not looking for blazing speed, just sport flying. All Ive ever flown were fox 35s..thanx in advance....Bob

Hi Bob

Back about 35 years ago That was the motor of choice for me, I had many Foxs of 35 ,29, 36, and several other brand engines, the OS 35S was in my opinion the best 35 out in that era, it was smoother and a little more powerful than the FOX 35 and would fly a pretty good range of planes from 480 to 600 sq. in.
The problems I saw that people had with them was that most came with a huge venturie the stock venturi was over .300 dia. This worked OK with the stock strap on muffler as it has a very tiny exhaust hole, many people used the Jet Stream bolt on muffler which was more open and with that setup the OS 35 broke very hard and ranaway sometimes, I used muffler pressure to help stop the hard break, but finally just set them up with 275 and 265 venturi sizes, this made the motor very nice on the  4/2 break. One of the "tricks" back then was to use a OS 15 or 25 venturie and a small ST NVA.
I always ran 1/2 castor 1/2 synthetic fuel of about 25% total oil and my engines lasted a long time. I still have all of the old OS and FOX 35s here, they are still in great shape after  100s and  100s of runs. Running a fuel of this type with 10% nitro 25 to 29 % oil is highly recomended and it will pay dividends in a longer life
Stan Powell visited here the other day and  looked at some of my old FOX and  OS 35s  from 30 to 35 years ago, he just smiled when he flipped the engines over, they still have tight front ends, great piston seals and the rods aren't worn out.
If you have any new OS 35s  there are several things you can do to it before running to help it last. One things is to put teflon pads in the wrist pin ends. you can either replace the rod of drill oiling holes in it, and set it up with newer mufflers , proper size venturies and NVAs

If you have other questions please ask

Regards
Randy
The weak point of the OS 35s  was the  Rod, piston wrist pin boss, and the wrist pin has metal pads in the ends which scarred the sleeve many times.
The rod was unbushed and would wear out pretty fast, I had a friend that wiped out 2 of his in just a couple of runs with a low oil content RC fuel