Well, here's another 'Fox" question(s) . . .
  
  I put together an S-1 Ringmaster last winter and the only engine I have that might be suitable for it is a Fox .25.  I did say "might be" because I know very little about the Fox .25 engines. This one is marked 'RC' on the case and has a bolt on c/l venturi.  No muffler or provision for one.   Here are my questions:

*Is the "Fox Burp" inherent to the .25 as it is with the .35 & .40 (perhaps others)?  
*Is there a boost port and might blocking that (if it has one) help?  
*Is the 'RC' ported differently from the standard c/l engines?  
*Are there any other NVAs that will work on the .25?
*Would a 9/5 prop be suitable for this Ringmaster/Fox .25 set up?
  
  I don't have any ambition to compete with this Ringmaster, just try and have some fun sport flying with it.
  
  I'm sure an OS, LA .25 engine would be a much better choice for this plane but the Sterling kit and Fox .25 engine were given to me by a friend and I would like to be able to fly it, pretty much, as it was given to me.
  
Thanks for any advice and suggestions.

Joe

If its the light 70s one, vertical intake, two weeny screws ,

they work rather well .Little ribs below exhaust port ,

usually a bolt hole over and under cenre of exhaust .

and / or lugs fore and aft. Take a .35 silencer .

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Theres a 19 the same but 1 fin lower , thats a howler

as the holes are the same size and the timings hotter.

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Like Nitro , will switch / change tone . 9x4 if its lugging.

these are the one piece case ones.NOT the B.B. schnerule.

Don't cheat on the oil either. The Engines don't have pads on the wrist pin and have been known to scour a line on the liner if abused.
Dennis

My flying buddy Tom has an S-1 ( average to slightly porky weight) with the 4 bolt  .25.  Stock except for a strap on lightweight tounge muffler.  10-4 wood  prop ( Zinger maybe?)
Good solid slightly rich 2- cycle run pulls the plane around on .015 X 60 with good tension and lap times around 5 secs.  No burp or funny run, stunts well and pretty easy to fly. It  seems to like a Fox Miracle plug with PowerMaster GMA 10% nitro all castor fuel.

Scott,

Well, I haven't gotten around to changing the NVA on the Fox.25 yet or trying the engine/plane.  That project got sidelined due repairs being made on another plane. Unexpected encounter with a field box while landing resulted in a broken wing.  Proves field boxes are allot tougher than planes.  Of course field boxes don't fly so good although I felt like hurling the thing as far as I could after the incident.  Though better of it because I would then need to repair both the plane and the field box. 

I hope to get the broken plane back in the air this week and will see what the Ringmaster/Fox.25 will do.

Regards,

Joe