tipstall 131

Hi guys,

I recently came into possesion of an OS max III .15 engine. It has the control line venturi and is in excellent shape. I would like to make it RC and fly it. What size carb would fit this little engine? I measured the carb from an OS .10 FSR and the carb spigot is a bit too short (and thin I think).

Thanks in advance.

downunder

These engines came with either a venturi or carb and that was the only difference between them. You'd probably only find a second hand carb by now although a later carb may fit. [link=http://sceptreflight.net/Model%20Engine%20Tests/OS%20Max-III%2015%20%282%29.html]Here's[/link] an engine test report on the R/C version and you'll see that the same engine was tested earlier but with a venturi fitted.

Ernie Misner

Cool article there from 1966! It appears to have a baffle on the piston and not be schnerele ported. (might need a plug with a bar) It bet it will purr.

Ernie Misner

tipstall 131

Thanks for the article and the feedback. I will measure the venturi spigot and look for a carb with the same dimensions.

1QwkSport2.5r

I'm necrobumping this thread... Got this old girl from a fellow clearing an engine collection he purchased from a collector. Among the engines in the box were a Max-H .40, Max .25, Max .15III, LA .25, FSR .25 (I found a NOS piston/liner for it), .60FSR, .46FX (2, one had a peeled liner), and a few other engines (there were at least 16-18 in total). I'm in the process of refurbishing this .15III. It appeared someone crockpotted the engine in antifreeze too hot and greyed the case and muffler. I was able to clean up the exterior and interior and reassemble with a new cylinder gasket. The engine needs a thrust washer (it was run for some time without one!!), but is otherwise complete and in operating condition. The muffler looks worse than it is, but I'm cleaning it up. My thoughts were to use a 8x3 or 7x5 prop to test run it, short idle bar plug (I have several to use up), 12% nitro/23% castor fuel, and a small 2oz tank using muffler pressure. It seems what has been said about these engines is they liked to rev, but if revved up past 15,000rpm they won't last long. If this engine survives the test running and runs nice enough, I may try using it in a small 1/2a Norvel trainer for kicks. I used LA Totally Awesome on the engine and a combination of the LA cleaner and Bar Keepers Friend kitchen cleanser. It seems to be a good alternative to the Dawn Power Dissolver that is almost gone.

1QwkSport2.5r

I got about half of the corroded gray color off and found the rest hard to get off... So I resorted to using the dremel and wire wheel to clean it up... Ended up shinier than the engine case - of which I think is a different alloy anyway. I probably wouldn't ever part with this one unless it wears out.

Mr Cox

The devil is in the details, in this case the piston to liner fit...
If the previous owner didn't simply boil everything, then perhaps it will be a good runner too.

1QwkSport2.5r

It has a nice "pop" to it turning it by hand without a prop, though the piston seal is a little leaky... That's expected to happen when disturbing the fit during disassembly. It feels nice and doesn't look too terrible. It will run at least, but how well is the question. FWIW, I don't think the "innards" we're cooked. It appeared as if it was dropped into the pot with all orifices plugged as the inside of the crankcase didn't look to have been "cleaned"... Only the outside. There was a layer of carbon under the piston crown. Definitely run with castor and some sort of storage oil used. The muffler was darkened inside and out.

gcb

If you run it with all-castor lube it may pick up a little compression.

George

1QwkSport2.5r

The compression is good, the leaky piston is probably due to the thin assembly oil I used. The glow plug washer leaks too, so need to replace it. The piston fit seems really good. My fuel mix for ferrous glow engines is 12% nitro, 22-25% castor and balance methanol. I never use synthetic oil in ferrous engines. Period. We'll see how it runs when I get to it. Have to finish running in an FSR .25 yet this fall.

TFF

Great engine for a floater airplane. Keep it rich as you know.

1QwkSport2.5r

Like they say... Lean is mean. (And don't over/under prop it.. This one isn't known for longevity in revved too fast or slow).

gcb

I used 8x4-8x6 on my CL stunt/sport planes. I think they were preferring 7x5 for Quarter Midget racing at that time. Never flew FF but I would guess ~8x3. The only RC plane I had a Max-III in was a modified Livewire Rebel and I used an 8x6 for that.

George

1QwkSport2.5r

I'll run it on a light prop for a tank or two and then stick a bigger prop on it. I found a few rpm figures on the Internet to use as a comparison to see what kind of condition this engine is in mechanically.

Thanks for the info.

SuperNash

I used a 7x4 on a Max-10 for a while (30 ish years ago now, borrowed from my dad, and it was already a vintage motor at that point) - went not so good on 5% nitro, OK with 10% nitro and better on 15%. Don't recall oil content. Probably part castor part synth.

I had the 10 on a 30" ish Cassutt... that was a fair handful