older os 25S

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draftman1
Posts: 367
Joined: Sat Aug 02, 2008 9:36 am

older os 25S

Post by draftman1 »

is anybody useing the older os 25s bb engines? I was thinking about getting them for practice and planes that new guys can try, they can be gotten pretty cheap.
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

I have had a few of the 25FSRs (still have one). The FSR is a wheezer and does not have a good stock carb, unless you only want to run WOT. I put a 40FP/Tower40 carb (10mm neck) on them, lower the head, and they still wheeze out high 13 to MAYBE 14k on a 10x4. They are nice running, lightweight, smooth reliable engines and I still have one in a practice plane that mostly gets used as a target tug.

The 25SF is a little heavier (not quite as heavy as the FX) and more powerful than the FSR, not quite up to the FX. It's an excellent running all-around engine in stock form. I've never tried running one with any mods, but a stock one is at least as powerful as the 25FSR with the mods listed above.

The FSR and SF have the same muffler bolt spacing as the FX so you can use the same stock, Macs, or MCP mufflers on them.
draftman1
Posts: 367
Joined: Sat Aug 02, 2008 9:36 am

Post by draftman1 »

yea, its the SF that I was thinking of, the fx is its replacement. I have been getting people to try combat and I cant keep buying FX's for there planes to try, I was looking for some older SF's that would be cheaper. the bushing type just wouldnt work that good and used FX's are not that plentyfull. thanks Scott
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

The FSR is not much more powerful than a bushing FP, the SF is more so. It's a real nice engine. I'm surprised you can get the SF cheap...lots of guys think the SF series were somehow awesome and better than their replacements, mostly because that was around the time OS became notorious for peeling liners. But the SF will peel, too, so look for that. The FX were really bad early on, but they seem to have solved it. IN the case of the FSR there were iron piston and ABC versions, I think the SF were either ring or ABC.
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

funny this should come up, i haven't seen one on the forums for awhile. I think the 25FX is much more popular/prevalent than the SF.

http://www.rcuniverse.com/market/item.cfm?itemId=497715
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