SOHC.co.uk Forums > CB750
750 F2 chain damage to gearbox
K2-K6:
For risk of leaking, many casting when they were more porous are painted internally to prevent this.
A decent coat of something oil resistant may be worthwhile here.
johnm37:
Well the top casing was much more difficult to weld. Durafix doest like vertical use. It just runs off into a large puddle. Its I also almost impossible to weld both sides of the casing. Heating up for the second weld just melts off the filler from the first. I went through a couple of rods before giving up.
My next attempt was better. I lifted the engine so the area to be welded was nearly horizontal. That gave a reasonable weld. Certainly strong enough for such a small area on the casing.
Having welded the inside of both cracks, I am going to reinforce the outside with epoxy putty. I use evostick putty. It's 2 parts of putty which you break off and nead together. I've used it before and it sets very hard. It can be sanded, filed, drilled and tapped. It also sticks to almost anything including hands so use gloves when handling it.
There's more room to use this on the outside. This should be the last step in the repair of the casings.
I would attach pictures but they're above the 3Mb limit on this forum.
johnm37:
I coated the inside repairs with Evo-Stik epoxy metal. It's more liquid than the putty stuff so can be spread on easily. The idea is to cover any remaining cracks to prevent oil leaks.
I will still reinforce the outside with epoxy putty.
philward:
Great work there John
Matt_Harrington:
John, that is good work. Based on that, I'm going to have a go with Durafix on one of my fins that has broken off. I think I'll use a copper (or s/steel) wedge between the fins and just weld from one side and see how it goes.
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