OS MAX Engines

I have recently picked up a couple of older OS MAX engines. One is an OS Max S 30 and the other is an OS Max S 35. The 35 is a bit varnished looking but seems to be in decent shape. The 30 looks almost like new. Neither engine has a needle valve assembly or a venturi. I bench ran the 30 with an (OS) venturi and needle valve assembly from an older 40 I had laying around and the engine seemed strong but wouldnt hold a needle setting. What should I go with for a venturi and needle valve assembly for these engines and has anyone ever ran an OS 30 S for stunt with any success?

Thanks

The 30 may not hold a needle setting until it is broken in. Then again maybe the venturi is too large. Just as an experiment, after ten minutes on the bench, try placing a piece of balsa wedge in the venturi and see if it holds settings any better. If so, get Leonard to sell you a venturi for it.

I have a couple of Max S 35's and a Max S 30. Leonard supplies venturis for these. I usually run a Super Tigre needle valve so have had good luck running a .280 venturi on the 35s. With an OS needle valve assembly, a .265 seems to work better. I use a .265 with a Tigre needle assembly on the 30. The engine works well with a 10X5 APC prop on a small airplane (Goldberg Buster)
Steve

Rick,

While Leonard sells an excellent venturi for the Max-S .30 and .35 engines as well as providing good customer service (And this Forum!!), if you're looking for some original OS parts for these engines, try:

[email protected]

DUANE COWAN
6298 FOUR PT. RD.
BETHEL PA 19507
USA

I bought several venturis and NVA's from Duane and Leonard a couple of years ago. Duane, like Leonard, does custom work on OS Engines and has parts around. He may not have any of these items left, but I feel that checking with him would be worth the effort.

I have had excellent engine runs from my Max-S .30's and .35's using venturis from both gentlemen. Make certain that you run them with a fuel having a relatively high oil content, most, if not all, of which should be castor oil. I use use 7½% nitro and 27% lube. 75% of that 25% is castor oil. I have yet to have any problems with any of my engines, even though the OS instructions I have on hand for these engines recommend using an all castor oil fuel.

Please DON'T use the commonly available R/C fuels (Cool Power is the worst offender!) with low percentages of all synthetic lube. You'll probably ruin the engine(s) in a few runs, especially if you have one or more really hot (lean) ones. If you have access to SIG Fuels, the Champion 5% nitro, 25% Castor oil runs well. If you can get Powermaster fuel, it's hard to beat the 5% or 10% GMA Blend with 29% all castor oil.

Good luck. Once broken in and running properly, I know that you'll enjoy those engines.

Paul

One note of interest: I recall GMA saying (before he fell ill) that he had a large stock of Max .30S parts (pistons/liners) on hand from converting customer's .30s into .35s, as nobody seemed to want the .30s...

Thanks guys for all of the good info. I mounted the 30 in the ARF Nobler I intend to use to teach my son the beginners pattern. I decided to go with the 30 instead of an LA 25, 40 or a Fox 35. The really neat thing is if the 30 doesnt cut the mustard the OS 35 S will bolt right into place. I hope to get the Nobler with the 30 in the air on Sunday so we will see if it has the stuff to pull the ARF. I havnt test ran the 35 yet and it is a little dirty and varnished. Someone told me a long time ago that if you really clean (internally) a varnished engine you take the chance of ruining the engine by srewing up the compression. Does anyone know if that is a true statement?

>Someone told me a long time ago that if you really clean
>(internally) a varnished engine you take the chance of
>ruining the engine by srewing up the compression. Does
>anyone know if that is a true statement?
Thanks Rick Henry

Yes.

>
>>Someone told me a long time ago that if you really clean
>>(internally) a varnished engine you take the chance of
>>ruining the engine by srewing up the compression. Does
>>anyone know if that is a true statement?
> Thanks Rick Henry
>
>Yes.
>
>
>

Can it happen?: Yes. Can it be fixed?: Yes.
Is it something to worry over?: NO...

LAST EDITED ON Aug-16-03 AT 04:31 PM (CDT)
 
> Thanks guys for all of the good info. I mounted the 30 in
>the ARF Nobler I intend to use to teach my son the beginners
>pattern. I decided to go with the 30 instead of an LA 25,
>40 or a Fox 35. The really neat thing is if the 30 doesnt
>cut the mustard the OS 35 S will bolt right into place. I
>hope to get the Nobler with the 30 in the air on Sunday so
>we will see if it has the stuff to pull the ARF.
>
There is one particular reason that many (CL) Max-S 30's ended up becoming 35's. The Max-S 35 runs like nothing other than a powered- up Fox stunt 35. They even sound the same. It runs a very nice 4-2-4 type of "classic stunt run". The majority of Max-S 30's I have heard about are far less willing to run that way. I have one myself that will not (but I do admit to greater experience with other 29's, like my NOS GH 29-S I'm flying lately).
>
That's not saying that the 30 isn't fine for the ARF Nobler. Just set it to run in a "Wet Two" like a more modern engine, although it doesn't turn up similar high rpm's. Try a paddle blade 9-6 prop, like an old TF wood, for a start, and don't load it down with a heavy plane the Nobler's size, that weighs over 43 Ounces (45 without a muffler).
>
>

.
Kiwi

****

LAST EDITED ON Aug-16-03 AT 12:55 PM (CDT)
 
the
>same. It runs a very nice 4-2-4 type of "classic stunt
>run". The majority of Max-S 30's I have heard about are far
>less willing to run that way. I have one myself that will
>not.
>>
>That's not saying it isn't fine for the ARF Nobler. Just
>set it to run in a "Wet Two" like a more modern engine,
>although it doesn't turn up similar high rpm's. Use a 9-6
>prop, and don't load it down with a heavy plane a Nobler's
>size, that weighs over 43 Ounces (45 without a muffler).

The Max 30s that I had all ran a constant two cycle - with the factory provided venturi - which just happened to be the same size as the one on the 35. A few years ago Leonard made a slightly smaller one for a Max 30 - and the engine performed a nice 4-2 break. Performance was almost identical to a stock Fox 35

For the ARF Nobler and the stock Max-S 30, I would go with the following:

1. Sig 25% all castor lube fuel, 10% nitro.
2. 10-5 Brodak or older Top Flight prop. Stay away from the heavier nylon and plastic props, as they increase the stress on the conrod and accelerate wear.
3. Tongue muffler. Muffler pressure, uniflow tank.
4. Launch at a wet two cycle and maintain that wet two cycle for level flight. It will lean out a bit in the maneuvers.
5. Adjust line length until comfortable with speed and tension.

I think the 9-6 will be a little fast in level flight and lack the thrust needed for the overheads.

Best of luck.