I am currently putting 100ml of oil to every 5 litres of fuel.

I thought it was semi synthetic but looked and its non synthetic at all.

It smokes a lot mostly on start up but still smokes white smoke when running normal.

What ratio should I use as i presume its runnign too rich.

Thanks

All the "official" mix ratios are available on beta uk site I imagine. I've been running 80cls to 5 litres for last 20 years on any of the modern makes you can think of with no problems (at least a semi synth) ..many will say leaner on fully synth. I wouldn't want to run my lawn mower on std 2 stroke oil ..only because I'm fussy about things like this. yours is a very broad question though so you will get a variety of answers.

I run my 2003 Rev3 270cc @ 70:1 I always use high octane fuel and only ever get smoke if i open it right up in 5th or 6th.