OS FSR engines

[Richard Acland]

The first RC engine I had was an OS 40 FSR, this was fitted to my first RC aircraft which was a Veron super Robot. This would have been in the mid 1970's. Getting sentimental in my old age I decided that I would like one of these engines again. In fact I have managed to get hold of two in quite good condition. I have had a good look inside to check everything over.

The thing is one of the engines has a ringed piston, and the other has what I assume is an ABC piston and liner. Which would have been the earlier engine, and why the change at some point. One of the engines came with a spare ABC piston and liner, would there be any point in fitting that to the ringed engine, or not.

[Robin Colbourne]

Richard,

'If it ain't broke, don't fix it'!

Have a good look in the exhaust port and if that and everything else looks and feels ok, use it 'as is'. Keep the spare piston & liner for when you really need it.

Selling my 40FSR is my big modelling regret. I'm keeping my eye open for one too.

Robin

[Nigel Dell]

As Robin says if it ain’t broke! ....

I bought both the 40 FSR and 40 FSR ABC back in the day, still got them! The ringed 40 has done many hours and though still giving good service, I treated it to a clean, new bearings and a new ring! It runs sweet and is stored away until I finish the new airframe for it.

The ABC however is the polar opposite, I had installed it in a Graphic 40, I had run it as per instructions and after 2 hours running it was not happy, the first time I had come across the problem of Nikasil flaking off the liner that OS went through, the piston and liner were replaced and it did another couple of hours running but I never really trusted it after that although it is still in fine fettle managing to retain its nikasil this time, it too is stored so I might use it but will be looking into getting the old liner re-chromed as a more hardy replacement in case it wants to snack on its liner surface again!

Still very good engines though, one of my favourites.

[Peter Miller]

I love the OS 25 FSR. I had one or two, the last was in my Swamp Rat

The OS10 FSR was nice but after a short time it would refuse to hand start. The late John Haytree warned me about that.

[Paul Marsh]

I have loads of FSR's from the 25, 40, 45's and the 50, as well as the 90fsr.

[Andy Stephenson]

If an OS engine has a ringed piston leave it as it is because the plating on a so called ABC regularly flakes on OS engines.

My OS 46FX had this problem twice as did my 1980s OS61RF. I still want to use it on a classic pattern-ship which is why I signed up to have a proper ABC replacement piston and liner made for it. There is a thread on RCG that invited people to sign up to a list for a guy in Australia who produces these. There are about 50 names on the list, I think this says it all about the nickel plating that OS uses.

A.

[FlyinBrian]

I thought the liner flaking started with the FX series, my 40 FSR was fine but the 40FX needed a new liner and piston plus bearings after a couple of hours running.

I also has a .61FSR which I used with an E.D. pipe in my Super Star, boy that was a powerful motor.

[Nigel Dell]

Posted by FlyinBrian on 01/02/2020 12:05:18:

I thought the liner flaking started with the FX series, my 40 FSR was fine but the 40FX needed a new liner and piston plus bearings after a couple of hours running.

I also has a .61FSR which I used with an E.D. pipe in my Super Star, boy that was a powerful motor.

It was bad with the FX but not started with that model by any stretch, I had a friend that went through liners in his ‘Hanno’ 61’s when competing in F3a with frightening regularity, he eventually found someone who could re-chrome, using chrome, his old liners and lap the pistons and this cured the problem.

He put me onto the idea of sorting the 40 which I never did as I had moved on by then but I was not alone with the problem with the FSR and that was from the guy who repaired my 40 at Irvine.

[Jesus Cardin]

I also own an OS .40 FSR ABC with liner flaked, althought it is a 40 years old engine and passed through 3 Omega model planes (old F3A aerobatic trainer), 2 Embraer Tucanos (semiscale model), a RCM&E Gerald Curd´s Bucker Jungmeister and an a Jack Stafford Ercoupe! So I can´t complain about engine longetivity.

I, like "FlyinBrian", also believed that the liner flaking problem was far more recent, from the mid 90´s FX models but it seems clear now that it comes from some years before!

Edited By Jesus Cardin on 01/02/2020 20:47:03

[Gary Binnie]

I restored this 90 FSR recently, shame that I didn't take any 'before' photos. The silencer is from an OS 108, the engine will eventually power a Goldberg Ultimate 10-300.

I used the carburettor for a while on an ASP120, it transformed it.

[Nigel R]

I have a few os abn types, none have peeled liners. Maybe I'm lucky?

If it were me I would just run the thing and worry about peeling if and when it happens.

[Engine Doctor]

The peeling liners were very prevalent on the 32 SX engines of the 90's It was so bad that Rip-Max were doing free rebuilds for a time until the range was changed I have a couple other sizes of SX and Fx with peeled liners . I had never seen it before the SX . It was obviously a fault in the OS plating process as the cheaper ASP/SC engines of the time ,although inferior in other ways never had the peeling problem . A few of the ASP/SC liners were a direct replacement for the OS parts as were some of the older Magnum parts for the FP range and were a fraction of the price !

I may be wrong but didn't this problem occur when OS tried to cut costs and engine production was moved to Tiawan. It was also when an altogether cheaper ranges of engines like the LA range and FL 70 four-stroke were introduced .The La 40 and above having Cylinder liners that feel like pieces of thin plated copper pipe ; although these didn't have the peeling problem as far as I know and last well despite the painted crankcases looking terrible JMO .Any attempt to clean them resulted in a silver LA

[Paul Marsh]

I even had a OS FP10 RN peel, mainly the 46FX's.

[Richard Acland]

Further to my original post. I have stripped both engines and renewed the bearings. After reassembly I started the ABC engine on my test bench to check RPM and set the idle. It is a real screamer with loads of power. I then set the ringed engine up to do the same thing. I could not get it to run other than the odd spurt. On checking I found the compression to be well down compared to the ABC engine. No problem I thought I will just fit the Spare ABC piston and liner which is new and all will be well. Not so. The 40 FSR ABC gudgeon pin is larger than the ringed gudgeon pin. This would also entail finding the con rod to match and a new gudgeon pin, what with old FSR engine parts being rarer than rocking horse droppings I didn't hold out much hope, still thanks to the wonders of the internet I managed to find the required parts and today fitted it to my test rig and she fired up straight away. So I will now sell one engine to help offset my outlay on parts.

 

Edited By Richard Acland on 06/02/2020 18:46:59

[Paul Marsh]

Have 4 OS 90FSR's, 2 here in box, one brand new, the other 2 in models. Got the new one for £15 including the shown silencer.

[Nigel R]

" today fitted it to my test rig and she fired up straight away. So I will now sell one engine to help offset my outlay on parts."

Don't be too hasty - I'd say you have the makings of a fine twin there