Legs in Boots,
Them's a lot of questions....so lemme try.
I bought the engines used (ie. broken in too much) back when I had a couple crashes in a row and thought I needed to stock up on expendable motors. I got two. Both came with the venturi. One had a pretty tired P/L fit, so I found myself only using one engine. Since then I found a replacement (NIP) P/L set, so I'll probably keep flying lighter planes with it since it runs really sweet.
One of the engines came with an R/C carb. The bore in the case is .359" ID with a depth (actually, carb length) of .352".
I've heard that the venturi for a 35S also fits, but I don't know what bore they have or if you need something a bit smaller. The 35S that I have is not stock, and has an ST needle valve so checking it does us no good. I don't know if any other stock venturis will fit. That's a good question for Air Ministry, who seems to have one of everything, and keeps track of crazy engine part swaps....
I found the OS .30S will pull a wood 9x5 Zinger (or 9x6?) pretty well. I run 10/25 or 10/28 all castor fuel with no issues. Twenty-five percent castor should be plenty, but I keep the 28 around for Foxes, and run whut I brung.
Jim Lee probably has or can make these. If you can't find what you need already out there, let me know. I temporarily have the ability to make these.
If you are breaking one in, then use a bit less pitch than your flight prop, and be sure the prop is balanced. No muffler. The OS instruction sheet says 30% castor for break-in and 25% after that. Lot's of short runs to heat cycle the engine parts, say 2 minutes each. If the fits are tight you may initially find that the engine quits if you pull the glowclip off. Keep going. Short peaking after a few runs. I would start flying it if it will hold a peak setting for a couple of minutes on the stand without overheating.
The Divot
"Leaving holes in the ground wherever airplanes are flown"
OS Break-in Instructions
Every OS engine is tested before shipment however additional running is necessary for long life and highest performance. Break-in your engine the following way.
1) Run your engine for a total of 20 to 30 minutes, with 9x5 or 10x4 propeller and a mild fuel. Let the engine run with a rich needle valve setting (4-cycle) at this stage, so as to avoid overheating. Running time is best accumulated by running the engine for periods of about 2 minutes with a short cooling-off period between each run.
2) Then, with the same propeller and fuel, run the engine with a 2-cycle setting, for a further 20 to 30 minutes. If the engine stops or the revolutions fall off at the maximum R.P.M. setting, your break-in is not complete. In this case repeat above procedure.
[Note that these are the R/C instructions, which is all I have.]
Topic: ...venturi size..? (Read 809 times)
