I am trying to settle my mind while contemplating the purchase of the OS.25LA. I have heard some, uncomplimentary comments regarding this engine. They all seemed to end up with scrapping the plastic back plate and needle valve and opting for a venturi mounted needle valve and I guess substituting a metal backplate. These were apprently in an effort just to get the engine to run properly. It seems to me that OS would be aware of this apparent "problem" and have done something about it. What info can the users out there provide for us on the "outside."
The Plastic back plate will work, however if you over torque the screws or crash you may start a leak. The leak can be hard to find and drive you nuts. If I had driven 500 miles to contest, and I got a leak, I'd be mad. So a preventitive swap out might be a good idea in that case. But on average, the plastic back plate will work just fine. If they don't leak they will be fine. If it starts leaking buy a metal one or send the motor back.
Is it a problem? OS is willing to put a 2 year warranty on their motor. If warranty claims were excessive due to a leaky back plate, there would be design changes. Warranty claims will kill a company, because they are costly to process. Any claim (aproved or deneyed) the comany looses money. So OS feels good about the nylon back plate.
On the remote needle valve, most guys would rather run a normal needle, BUT the remote needles do work.
It depends on your definition of a good run. Stunt guys are very picky. The remote NVA has several extra places where a leak can occur. A lot of guys want to eliminate any potential problem (real or not) , so just toss it.
I have had good luck with remote needles, but I have removed them form the back plate. Remote NVA's can be moved to be more protected in a crash.
This is in the combat section and NVA's are the norm here, but most swap the stock one for one off a OS .10 (finer thread) when used on pressure.
In most applications the stock OS will work just fine out of the box. If you are a high end stunt competior, you may want to make changes, but most sport fliers will never have a problem.
If the back plate and NVA scare you purchase a Brodak .25. While more expensive the NVA and back plate are more conventional.