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Engine basics => Engine set up tips => Topic started by: jim gilmore on January 27, 2009, 05:27:41 PM

Title: OS .25 la
Post by: jim gilmore on January 27, 2009, 05:27:41 PM

I have an os 25 la now and am going to use it on a model. I can either add a spray bar and a venturi or neeedle valve and venturi. If I wish can I leave the old backplate on and use just the new needle valve with the plasticky back plate or does that have to be changes. Also could the needle valve on the back plat be trimmed off if I so desired  with out affecting performance ?

Title: Re: OS .25 la
Post by: Mark Scarborough on January 27, 2009, 05:42:01 PM

In my experience with the LA 25, the most vulnerable part of the plastic backplate is that arm for the remote needle. It runs ok with it, but lord help you if you smack the ground, then that arm breaks off and makes it likely to leak. Myself, I carved, cut and filed the arm off, used a normal needle assembly, and never had a problem with the plastic backplate, just dont overtighten it

Title: Re: OS .25 la
Post by: ray copeland on January 27, 2009, 08:21:04 PM

What Mark said about overtightening the backplate!!!  n1  I now have 2 in the junk drawer !!!

Title: Re: OS .25 la
Post by: Terry Bolin on March 15, 2009, 07:54:20 AM

Use a venturi and spray bar up front. I use some silicone (Black, not ultr-black) around the plastic to crankcase seal. it works well. But move hte NVA up front for best runs. Great motor though.
Terry