Whats the best ratio to run in a 1986 250R? It's bored out to 310cc and has just finished being broken in.

 

Depends on your compression. You should be able to run 40:1 or 32:1 perfectly fine in a 250R. I've heard both,that 40:1 is better then sometimes 50:1. Do you know your compression numbers?

 

Also, does a paticular riding style require a certain ration. Say, trail riding, whats the best ratio for that. I'll still have to check compression

 

Probably 40:1

 

I don't think it matters for certain riding situations.
If its tight slow trails. The 250R will NOT be happy going slow.
I still think the best is 40:1.

 

Buy yourself a ratiorite that'll tell ya.

 

Depends on the oil.
A high quality synthetic can be ran at higher ratio's and still provide as much, or more protection than the conventional oils of yesteryear.

Two mixes that I have used, and am happy with performance, and protection wise;
Golden Spectro 40:1
Amsoil 2000 fully synthetic 50:1

 

Well I was half right.

 

I also run a 310 kit and I run Amsoil 2000 at their recommended 50:1 ratio, I haven't had any problems. Whatever oil you choose, just pick a good quality oil and stick with it.

 

I will swear by Golden Spectro. I've been on the same plug for about 6 months. I use to mix at 50:1, but I am in the process of breaking in my top-end so I am using a 40:1 mixture and richer carb. settings, but still haven't fouled the plug(knock on wood)