What if any, are the differences in running characteristics between the fp & la series of os engines.  Specifically the 25s. I have both and want to use one to learn the stunt pattern with a ringmaster Or flite streak
Thanks in advance.
Tim

The LA 25 and the FP 20 run about the same... as long as they have the same E2030 muffler.  The other muffler (842?  I'd have to check my parts box) is not desired, and if you have the other muffler it probably means you have an IRON FP as opposed to ABN.  This difference matters little as you need to use fuel with adequate oil in it.  The ABN is preferred. I have the iron line FP20 though.

Tip: use a very strong rare earth magnet to see if the liner is iron.  It will stick through the case.  With a lesser magnet you have to go in through the exhaust.  All LA's are ABN, as far as I am aware.

While front NVA is preferred the remote is fine.  The molded remote NV will need some crash protection, I used a rounded off triangle of aluminum, mounted with the engine lugs on my flite streak.  The plastic is not friendly and there is no good position to switch the back to.  The remote NVA on a bracket CAN be positioned well.

The APC 9-4 is a good prop, there are some others too
http://www.aeromaniacs.com/brett.htm
http://stunthanger.com/smf/open-forum/skyray-35/

Read these  Pay attention to fuel system setup and RPM.

Have fun!

Phil

While front NVA is preferred the remote is fine.  The molded remote NV will need some crash protection, I used a rounded off triangle of aluminum, mounted with the engine lugs on my flite streak.  The plastic is not friendly and there is no good position to switch the back to.  The remote NVA on a bracket CAN be positioned well.

If you have it, the remote needle on a bracket is great for beginners.  Relocate the bracket so the needle is parallel to the cylinder and behind it.  Then, when you crash, you don't have to go get a new needle valve.

You *do not* want to replace the NVA or venturi with a "better" one. The one that comes with it is better and you lose a tremendous amount of power with the larger ST-sized spraybar, and once you do it, it's hard to go back because you have to drill out the case.

The OS "non remote" needle and spraybar may still be available from Tower.  If so, this would be the one to use because the spraybar is the same size as the remote spraybar.  I have a 25LA that flies just fine with this combination.

In general, listen to Brett.  He's done a lot of experimenting with these engines, for no other reason than to share his knowledge with the rest of us.

I tried. With the remote nva molded into the backplate it just doesn't work.  There is another, older version that has the remote needle on a separate bracket like on the larger LA.40.  This one can be located in a much better manner.


http://stunthanger.com/smf/building-techniques/oops-1-12-degree-error-should-i-worry-about-it/msg397391/#msg397391

  The older bracket-mounted needle valve is actually the core of an R/C carburetor, so if you converted it, all you need is to disassemble the old carb to get the needle out of it, use the existing "nozzle"/spraybar from the molded-backplate version, and make a bracket for it.

   They used to sell the carb core as a remote needle conversion kit. That's what I used for my Fox 35 remote needle experiments. It worked fine but it didn't solve any of the important problems (burp or severe vibration and ...).

    Brett