thought that I should post about the root of this problem.
Back when I first tore the motor down to build the 904, I noticed a crack in one of the header ears (where it bolts up to the head). That is a cast stainless steel part welded to a double wall stainless tubing.
I took it to a local shop that does very good work. They fixed the ear and noticed another crack and welded that too.
All good for a lot of miles.
It looks like the weldment on the lower frame rail that the header rubber mounts to, failed. It is a sheet metal tab (steel) welded to the tube of frame rail. It appears to have been a cold weld, so has been that way since day one. When it failed it put the load on the previously repaired header and that cracked right thru the repaired area.
Amazing that it didn't fall off entirely while I was riding!
Last edited by mag10; 07/21/2023 8:47 AM.
05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter
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