I would suggest Eric Gorr his his place is called forward motion hes a great guy to deal with and one of the best 2 stroke engine builders! But he is in the states but his prices were better than anybody I could find in canada. He will give you the most power and reliability! He built me my engine Its a rm 250 with a stroker crank and a big bore so it makes it a 315 stroker and it rocks! I cant find a 450 that will touch it! Give him a call and quiz him he will be able to answer and questions you have and be able to build it to your liking.
We have been racing motocross in Canada and the USA for about 8 years. There is only one engine builder that we are aware of in Canada and that is Bondi Engines out East. That being said we have never used any Canadian builders do to the fact that the proven engine builders for Minicycles and larger bikes all come from the US. Im by no means saying there isnt somebody out there in Canada that can compete but everyone we race including ourselves has gone south when it comes to Superminis and motors in general. Depending on your budget I would reccomend Pro Circuit racing in Corona California, we had a number of Kawasaki superminis and 85's built by them and I tell ya there is not a bike around in that class that could touch these. They build a very reliable 109cc supermini. Is the bike you are building into a supermini currently an 85cc or is it a 105cc? if it is an 85cc I believe Yamaha also builds/sells a 105cc kit that can be easily installed on the 85cc.
yz 85 currently building it to a supermini. We have one yz 85 built by EBR and yes the bike rips. This is his first super mini as he will only be 11 next year but can race it in Calgary at their super series, but not in the CMRC for another year.