Is there any oil additives you would recommend for older quads to help reduce smoke at start up or to help condition the engine?

 

I'm guessing you are referring to stuff like Slick 50?

I seem to remember a few years back a discussion about that. Seems like a good idea, except stuff like that would be very bad for wet clutch system.

I had considered maybe adding some to the Polaris I own, since it has no wet clutch system. Never did, so I can't say that it's a good or bad thing for them.

Motor honey comes to mind, but the best thing is just a rebuild on the top end at the very least.