harley p

could anyone tell me if a old (but hardly ran) os surpass 120 super charged engine could be converted to a naturally aspirated engine. and if so what it take to do it ?

w8ye

My Feedback: (16)

Back plate
intake manifold
Carb

harley p

thanks for the reply, i will take that for a yes. has anyone else tried this conversion and if so with what results?

JRO

I just converted my OS surpass 111, removing the pump, carb, and regulator. I also replaced the back plate, which I understand you don't need to do. My engine runs great now, I just couldn't get the other set up to work for me. Tower Hobbies has the necessary parts.
You are looking at around $100.00 for the conversion. To me it was worth it. You will also need a nipple for the muffler.

w8ye

My Feedback: (16)

On the super charged engine you have to replace the back plate because the drive for the supercharger was through the back plate

harley p

thanks for all the help, i will give it a go

JRO

When I called OS engine at Tower Hobbies they told me all I had to do was put a plug in the line coming out of the back plate. I still got a new back plate. I noticed there was a little difference on the mounting for the carb on the new back plate. I figured after buying the Carb. and manifold I may as well make sure I have it done right and got the back plate.
Like I said I am happy with the new set up.

gkamysz

My Feedback: (19)

Don't the supercharged and old geared pump versions have a nub on the crank pin to drive the SC and pump? Does a regular backplate fit in this case?

Whats' wrong with your supercharged engine that you want to convert it?

harley p

greg, the engine runs fine on the bench but quits in the air, it was sent back to os and came back the same if not worse. anyone i know that has one has had the same problem so it has been in its box for many years and it would be nice to get some use out of it.

gkamysz

My Feedback: (19)

I guess they have the same issue as the geared pump version. That is, they are so old now that the regulator diaphragms are stiff and don't work well. I have two of the geared pump versions like this. I'm trying to work out a solution to the diaphragm. I keep looking for a SC version to add to my stack, but they are often overpriced used and sell high when NIB.

Campgems

I started up an O.S.120 Surpass today for the first time. It is my first pumper, and I'm not quite sure what to expect. The engine starts easier than any I've had. Coulldn't believe how quickly it started. I let it warm up for a while and then started leaning out the high speed. I got it rear top by ear. Then it was into the trailer for our club meeting. when I got back to the plane, there was a puddle of fuel under the engine. Not big, but the nose wheel was wet. I started it up agin, and again, it started with the first couple revolutions of the starter. I was doing some servo trim on the throttle and I noticed fuel dripping off the needle valve. I killed the engine, and I m not sure where it was coming from, but it looked as if it was coming off the top of the carb. Actually the left side if the engine was upright and looking from the pilots seat. I suspect the diaphram in the regulator is a gonner. I would be really interested in diaphram solution. I havn't torn the carb down yet to see whats going on, That will probaby be next week.

One more quesion on these engines, do they wheeze when turning them over by hand? This one makes some strange noises and it continues when running at idle. It runs great other than the leak and wheeze at idle.

Don

gkamysz

My Feedback: (19)

Don, which engine in particular do you have? We are possibly talking about 4 different engines in this thread.

1: OS FS-120S-P with C-12 carb and gear pump
2: OS FS-120S-P II With C-13 carb and gear pump
3: OS FS-120S-SP With C-14 carb, supercharger and gear pump
4: OS FS-120S III with new type diaphragm pump and plastic cover on carb regulator.

Campgems

Greg. it is either #1 or #2. I'll have to pull it out of the plane to get a look at the plumbing arangement. I believe it is #2 though.

Don

gkamysz

My Feedback: (19)

I have the first one. It has a very normal looking carb. The C13 carb has a regulator on it.

Campgems

It the regulator carb. I think it is the regulator that is leaking. Probably a blown diaphram.

Don

w8ye

My Feedback: (16)

Too bad we cannot whack out a new diaphragm

proptop

My Feedback: (8)

I just got done assembling a pumped O.S. / Magnum "hybrid" I guess you could call it...

A friend gave me a damaged (cracked case that had been welded...then it dropped a valve ) O.S. 1.20 Surpass (the 1st version with the pump and C12 carb ) and an almost new Magnum 1.20 that had a bit of a bumpy landing...(bent N.V. and carb mount on backplate, and messed up the exh. header threads )

I swapped a bunch of parts around and now have a Magnum case, cam and valvetrain, and the O.S. head, crank, and pump / carb...etc.

The crankpin is extended on the pump versions crankshaft....I don't think a std. backplate will fit without grinding or cutting off that extended portion.

gkamysz

My Feedback: (19)

I'm pretty sure I can make a Walbro diaphragm fit the engine with the C12 carb. The problem is getting the old one apart without damaging it and having to make new parts. I haven't seen the regulators for the C13 carb.

Iflyglow

My Feedback: (79)

Why does OS quit supporting there engines as soon as they are discontinued.[X(] That is the reason you could not get me to ever think of an OS with any kind of fancy fuel system. They could atleast supply the Diaphrams for the carbs, and pump parts. The parts for the OS 1.60 FI and .91FI are non existant allready. You can buy any part you want for an old YS.

Campgems

I think not selling parts to the regulator and pump is a business model common in Japan. I've got an old Lexus and the speedometer needle is sticking when it's cold. I called a couple speoometer repairshops around the state and none will touch it, or any model Japanese speedometer because like the regulator and pump, it is sold as a unit, IEthe entire dashboard. No parts are avaiable. Also, like OS, parts are no longer avaiable.

What is the diaphram made of. Is there a fiber center or is it just a rubber compound. The reason I'm asking is that Ihave a vulcanize press for making molds for jewelry. It probably wouldn't take much time to make a metal mold for the diaphram and if my rubber mold material would hold up to the fuel, Imight be able to duplicat the piece.

Don

gkamysz

My Feedback: (19)

It's an impregnated cloth. Seems to be just like the Walbro diaphragms.

Bax

My Feedback: (11)

O.S. supplies parts for discontinued engines for at least five years after manufacture of the engine has ceased. After that, the demand for parts becomes so low that they cannot economically make parts even if they took orders for a full year and then made only the parts ordered. We'll support O.S. engines as long as there are parts...even when some parts have ceased to be manufactured, there can be residual stock left over.

If an engine was extremely popular, O.S. may make parts for more than the five years after manufacture.

blw

My Feedback: (3)

Thanks, Bax. Another urban legend bites the dust.

Iflyglow

My Feedback: (79)

Bax,
Why does OS not sell the Reg diaphragm's and pump parts seperately for there engines? There are a heck of alot of 1.20 Surpass 2 and Surpass 1 pump engines out there that are paper weights because there is no simple parts support for the fuel pump's. YS sells any part you want for the fuel system seperately and for many many years 20+ afterwards. To have an engine that costs several hundred dollars sitting not useable because of a $3.00 diaphragm or pump part is crazy. You can buy allmost any part needed to keep a 20+ year old YS running. For example.

YSE0905 Engine O-Ring Set $16.95

YSE0730 Diaphragm $3.10

YSE0176 Regulator Plunger $3.10

YSE0180 Plunger Spring $1.50

YSE0900 Gasket Set $10.75

gkamysz

My Feedback: (19)

Not being familiar with YS, are those the same parts they use in current production engines?