I'm working on converting an Echo 58cc. I have often cut off the crank even with the rear bearing and plugged the block where the seal normally goes on my various Echo engines. The 24cc and below engines have cranks that aren't so hard, and it isn't very difficult to cut them off. But the 25cc and up cranks are HARD. It took me a while to cut off this 58cc crank.

Benefits:

Less seal drag.
One less potential leak point.
One ounce less weight. (I weighed it out.)
If you want to mount the crankcase flat to a firewall you have to cut part of the crank off anyway.

Is it worth it? Probably not....

Anyway, here's pics of this one. I have used modified car engine freeze plugs to block off where the seal would go before, but this time I "whittled" a plug out of Delrin plastic on the lathe.

AV8TOR

I knw you did this mod before.I havent done it yet to any of mine but im going to i think.Besides an extra leak,whats the RPM gain?
I also use a 4 inch angle grinder with a metal cut off blade[thin].
Takes about 30 seconds,no matter what crank.Used this on my Husky 61cc.

wouldnt this put more stress on the front main bearing? What if you were to cut the shaft so it still uses the other bearing, and have a shallow plug pressed in just where the seal is.

He still uses the rear bearing

There's minimal gain in rpm

The gains come from ease of mounting and the less potential of a crankcase air leak.

Yes, I definitely still use the rear bearing. The plug is shallow and just replaces the seal. The crank is cut so that it still fully enters the rear bearing.

I doubt if one could measure a power difference just from the seal drag, though the seal drag is noticeable when you turn one over by hand without the piston/cylinder installed.

AV8TOR