Wow guys when these things blow up they really blow up!!
I opened her up and both pistons were up.. never a good sign on a 180 twin.. The bottom half of the left piston is gone.. The wristpin is still in the rod but the rod is broken and bent in ways previousely unimaginable.. the crankshaft rod journal of course is wasted.. and the left cylinder sleeve completely destroyed at the bottom..
O.k. Guru's.. I see a number of posts about broken rods, pistons, cranks.. what is this engines weak point? One of these or all of these? I'm not going to build an all out race bike but I haven't forgotten how to twist the throttle either.. so that means if I'm going to build a motor I'm going to address it's weak points.. what are this engines weak points and what are my options guys?

I'm not an expert here, but my general impression is that the weakest point is the crankshaft, and/or con-rod big end bearings. Unlike most of the rest of the GS-series bikes, these twins have plain bearings.  Most GS's have roller bearings on the crank mains.  You should check race tech sub-forum. I bet you'll find plenty experience there.

I've also seen and heard of broken valves but don't have a good sense of any single point of failure in the valve train.

Also check in with the GSResources web forums.  Good info there too, but largely aimed at the four-cylinder crowd.

Quote from: 5thAve on May 06, 2011, 09:09:00 AM
I'm not an expert here, but my general impression is that the weakest point is the crankshaft, and/or con-rod big end bearings. Unlike most of the rest of the GS-series bikes, these twins have plain bearings.  Most GS's have roller bearings on the crank mains.  You should check race tech sub-forum. I bet you'll find plenty experience there.

I've also seen and heard of broken valves but don't have a good sense of any single point of failure in the valve train.

Also check in with the GSResources web forums.  Good info there too, but largely aimed at the four-cylinder crowd.

No single point of failure should be a good guess. I've heard of counter balancer bearings go, one clown lost 2 motors via rod bearing seize, there have been the bind and break thing on valves ... of course there is the ever popular goats killing the bearings like it did on goats bike.
Cool.
Buddha.