OS 21TM - Seal it or not?
 

Got a brand new OS21tm sitting on the bench. Seal it or not before install? If so, with what?

Don't bother. It's sealed with o-rings. Absolutely no need whatsoever.

That's the way I was leaning towards. The only reason I was considering it was cause the 3.3 traxxas engine I pulled had engine leakage issues. It was about the 9th RC car engine I've had over the years, first one with leakage issues though. I'm thinking just run it!

Where did it leak from?

I couldn't ever figure it out. I dissected it, sealed it putting it back together, checked gas tank seal, gas lines, air intake, exhaust... everything. Couldn't figure it out. It wouldn't hold a tune for anything. Never had an engine act like that. Bought it used so I don't know how it was treated prior, it never ran great really. So I gave up on it, bought this OS (which I've heard lots of good things about), and just wondered if I should bother sealing it from the getgo or not. I have heard of guys who won't run an engine at all w/o sealing it. If I've ever had reason to seal a motor, it was this last motor I had. But if it'll help me avoid the problems I had with this last motor, I'll do it.

I've had a bunch of Traxxas engines. Most of the "air leaks" people spoke about was actually just due to improper carb setup. Tons of people are told via instruction manuals that a 1.0mm idle gap is normal and that is the heart of nearly all tuning problems.

If I have an engine that won't tune right, the first thing I check is the fuel system and carburetor. If that checks out, then checking the piston/liner fit is next. A poor fitted piston will cause the engine to not idle right and nearly impossible to tune. A properly setup engine will sometimes weep a little oil from the front bearing, but it shouldn't be much and is normal.