I have an Exceleron with a YS.91 in it. The problem is that the YS was in a crash, and I cannot get it to run right now. It does not idle well and sags real bad at mid range, and does not seem to be putting out a lot of power. I am considering sending it to YS Performance, but am not sure it is worth it. I'd like to put a .110 in it, but just can't seem to find one.

Is it worthwhile to get this thing repaired, or just find a new engine?

Definitely worth trying to get it repaired! Check for subtle damage that might not be immediately apparent - hair-line crack in the rocker cover for instance, or a slightly damaged or displaced o-ring sealing the push rod covers, all things that could happen in a crash and they will all screw up the running.

If you can't find anything obvous then send it to YS Performance - and try posting on the YS support forum:

http://www.rcuniverse.com/forum/forumid_197/tt.htm

James