Xjet; Im with stelios on this. There might be a balance issue on the counter-weight.

Even the best bearings will become rubbish rapidly in a hostile enviroment.

I personally never buy bearings from hobby shops or online stores. I go down to industrial ball-bearing stores, and buy with a brand name. NSK, NTN, SKF are my choices (which are used in 99% of glow engines on the market today)

And you can virtually find any type of bearing you want for much less money than any online hobby store or online glow engine bearing store..