One of the reasons I bought a sandcast was to learn about more about the CB750. 2659 has not disappointed. After getting the bike last May, I've discovered some surprising and not-so-surprising issues. Yesterday I pulled out the airbox, which when mounted showed a crack on cyl 1 end and a crack across the bottom between the two wing nuts. Disassembling it on the bench it now shows much more: there's a horizontal crack between cyl's 2 and 3, 3 and 4: the upper section is warped, squashed a bit on the side of cyl 1; the plastic intake tube face is a bit concave on the cyl 1 end; and the center section of the airbox is also warped on the cyl 1 end. Not sure what caused the warpage, but my first thought is too much heat...…..but heat from what? a frequent backfire? why on the cyl 1 end only? Maybe the cracks may have been caused by assembling warped components. Also, the rubber intake tubes are all very supple, except the cyl 1 and cyl 2 tubes have a hardened edge on one side of the tube only.
To repair the damage, I'm thinking heat gun, but would this produce enough heat to reshape the warped areas? What approach should be used to minimize the probability of causing further damage? Any ideas for a "form" or "jig" to aid in the reshaping?
Any help and guidance would be appreciated.
John
