Hello I just rebuilt my motor on my 90 LT 250R, I bought a new cylinder, new wiseco piston, and new reeds.

I was wondering if I should use Synthetic pre-mix (ams-oil) or petroleum based pre-mix to break it in?

 

It would be best to run petrol based premix for the first couple tanks, there's more friction, so the rings will seat better.

 

thanks man! whats the best brand?

 

My cousin uses castrol, he gets it at advance auto parts. I don't know if it's the best, but it seems like it does what it needs to do, and it costs less than anything else we've found so far.

For the first few months my cousin had his 86 quadracer he used golden spectro premix because that's what the previous owner used, and it lasted until 2004 on the original piston, rings, and cylinder bore! It made it smoke more than normal though, and it was too expensive, so he switched to castrol.