Hi Bax,
Thanks for the info on the ST G 90....

Just concerened about the quality of the 91FX? Have read a lot of bad things about this engine concerning the needle valve and bearings...have also read that OS has since fixed the problem. This is the only 90 sized 2 stroke engine available in India... So before I go ahead and buy it just wanted to get your opinion on it..... How does it compare to the G 90 vis a vis power, reliability/longevity?

Can I use Master Airscrew K-Seriese 4 stroke props on the OS 91 fx or for that matter any other 2 stroke engine?

Please bear with me about these questions..... as the choices here in India are vey limited.

You would not go wrong with either a new O.S. Max .91 FX or a new SuperTigre G-90 engine. Both are excellent engines that give good power and longevity, with proper care.

So-called "four-stroke" propellers are only those props that have diameter/pitch combinations that have proven to be effective with four-stroke enignes in the suggested size range. They usually are a little-higher-pitched for the diameter when compared to two-stroke propellers. If they allow your engine to run well and the airplane to fly the way you desire, they are OK to use.

Thanks again BAX and a belated Happy New Year.... one last question how does one distinguish the "new" OS 91 FX from the old one?

The newer versions have a plastic needle holder on a bolt-on bracket at the rear cover.

Ηι there!
Just got my NIB OS 91 FX!
You will not have any problem with this engine,if properly used!
Enjoy...

similar to the 1.60 fx needle valve?

I checked it out and it looks like the same assembly as the one on the .46 AX.