OS Max 25 RC engine??? (not fp, La, or any other designation)

**RknRusty** Tue Jul 15, 2014 2:52 am

I bought an OS Max 25 RC engine on eBay because it was listed as an fp, but it's not. The markings are just Max and 25 with a small strap-on muffler. Navion said in another thread it was a '70s engine and apparently pre-dates the fp, S, and LA series. Can anyone tell me if this will make a good CL conversion and will it use an fp venturi or have I got to custom make a venturi for it?
Rusty

pkrankow Tue Jul 15, 2014 7:59 am

Pop the muffler and get a good light to see if it is a baffle top piston.

If it IS a BAFFLE TOP piston then it has the older style porting (before Schnuerle) and the engine, while a solid performer, is not going to make the power of newer engines.

If it is a FLAT TOP piston then it has the newer porting, although may or may not be Schnuerle, and will have much better power for its displacement.

As for converting I suspect you can use LA or FP parts to do the conversion just fine. I am confident the diameter of the intake seat has remained the same for quite some time.

Phil

navion34 Tue Jul 15, 2014 8:03 am

I use it as a CL engine wit the throttle wide open...

OVERLORD Tue Jul 15, 2014 8:59 am

Rusty, the control line version of the OS MAX 25 RC is called the OS MAX 25. I have an OS MAX 15 of the same series. They have a baffled piston.

Look at this RCG page for the OS manual. Just scroll down a bit

http://www.rcgroups.com/forums/showthread.php?t=955929&page=17

Lieven

**RknRusty** Tue Jul 15, 2014 10:17 am

pkrankow wrote:Pop the muffler and get a good light to see if it is a baffle top piston.

Baffle top. Maybe good stunt engine for a smallish plane. Sometimes the Schnuerles get an attitude and run a little wild.
Rusty

crankbndr Tue Jul 15, 2014 12:44 pm

OVERLORD wrote:Rusty, the control line version of the OS MAX 25 RC is called the OS MAX 25. I have an OS MAX 15 of the same series. They have a baffled piston.

Look at this RCG page for the OS manual. Just scroll down a bit

http://www.rcgroups.com/forums/showthread.php?t=955929&page=17

Lieven

On that page I found a large number of engine test reports, thanks!

http://sceptreflight.net/Model%20Engine%20Tests/Index.html

**RknRusty** Tue Jul 15, 2014 3:14 pm

That's a great list. I'd forgotten about it and in fact let the bookmark get lost in a browser changeover. Thanks for pointing me to it.
Rusty

GallopingGhostler Wed Jul 16, 2014 12:01 am

RknRusty wrote:That's a great list. I'd forgotten about it and in fact let the bookmark get lost in a browser changeover. Thanks for pointing me to it. Rusty

http://sceptreflight.net/Model%20Engine%20Tests/OS%20Max%2020.html
is actually about the OS 25 S and RC, seems to be a decent engine, more powerful than the 19's of the day. Perhaps it is on par with the Fox 25 baffle piston, except lighter?

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OS Max 25 RC engine??? (not fp, La, or any other designation)

OS Max 25 RC engine??? (not fp, La, or any other designation)

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Re: OS Max 25 RC engine??? (not fp, La, or any other designation)

Re: OS Max 25 RC engine??? (not fp, La, or any other designation)

Re: OS Max 25 RC engine??? (not fp, La, or any other designation)

Re: OS Max 25 RC engine??? (not fp, La, or any other designation)

Re: OS Max 25 RC engine??? (not fp, La, or any other designation)

Re: OS Max 25 RC engine??? (not fp, La, or any other designation)

Re: OS Max 25 RC engine??? (not fp, La, or any other designation)