I've seen that happen to pipes when the system wasn't done right.
That said, we now have a couple of different ways the primary pipe sits on the cylinder. One is with a slip joint, the other is with a hard held flange.
The slip fit allows for a bit of slack movement between the engine and pipes, and that allows different forces between engine and pipes to go their separate ways. If an engine is solid mounted, and the pipes are solid flange mounted, the pipes need to be rubber mounted, to allow for the movement that always occurs between both engine and pipes.
We had a lot of this happen on the F5R/F9R, as they had a solid mounted engine and solid mounted pipe, with a slip fit at the flange. Even worse when the factory tried to solid moount the primary pipe to the engine. What fixed Yvon's setup was with solid mounting the engine to the frame, slip fit the pipe into the cylinder, and mount the pipe to a framework bolted to the engine, not the frame. That stopped the pipe fracturing.
We used a side Lord mount for the 500/750's, and they allowed a lot of engine movement in the chassis, slip- fits into the cylinders, but, solid pipe mounts. When we went to rubber pipe mounts to the frame on the later H2R's, pipe fracture problems stopped.
H1 is a classic, early and late engines are solid mounted in the frame. Early pipes are solid mounted to the frame, but, use a separate muffler and primary pipe, with an insulator in the junction. that insulator is also a vibration plane separator. Engine doesn't try to tear up the pipes. Later H1, same solid engine mount, one pipe, primary pipe and muffler welded together, but, mufflers are rubber mounted at their flanges to stop one vibration/movement plane from adversely effecting the other. Two different methods to attain the same end.
Of course, if the welds are sub standard, nothing will stop pipe damage.
Hawaii Mike, I can see your pipes are solid mounted at their rears, behind the weld failures. How is the engine mounted, solid, or rubber, and, primary pipes, slip fit or solid mounted in the cylinder???
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