Hello,
What's the difference between and OS .25 "FP" and OS .25 "LA"
They are both bushing engines, but what else??

The "LA" has replaced the "FP" series of engines.

The LA engines have rear needle valves which can be more difficult to fit fuel lines to.

Dave Segal

One's blue ? Tee Hee

There really isn't too much difference between these engines... The FP is a bushed engine with an airbleed carb and the LA is a bushed engine with an airbleed carb. Since the FP can be fitted with a remote needle for about $10.00 there is no difference there. I think the FP is a much better, stronger, and more durable engine than the LA. 25 FPs can regularly be found here and on eBay for a very reasonable price.

I appreciate the responses. I just picked up an AT-6 for pylon racing and that was the engine installed. The rules allow either the FP or LA and I could not find any info on OS Engines website.
Now I know.