It's going to take more than an extra ring to get the power of the old motors up to that of the new one. The new cylinder has a larger more "D" shaped exhaust port that is unbridged. The best that I can remember, the transfers ports are a little different too, but don't quote me on that, it's been a little while since I've had them apart to compare. I really can't see why the guys want to buy the old refurbished motors from Harbor Freight when you can get a new twin ring from Wal-Mart for around $69. There is a big difference in power between the old one and the new one.