SOHC.co.uk Forums > CB750

750 F2 chain damage to gearbox

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Bryanj:
All te side cases come off then you unbolt all the case half bolts and remove the lower case

K2-K6:
Welcome to the forum John.

What a shame to get caught out with that. Ultimately it needs to be welded I agree with you on that, wouldn't stick the broken bits back in with it in situ. If you want to delay the work then you could make a thin patch in aluminium to cover the hole and epoxy that to the surrounding surface as temporary cover.

To remove the bottom case as noted, I'd also thoroughly clean them all outside firstly to avoid any extraneous grit etc from finding it's way inside as you're not going to strip it out completely. 

I like the F2 model and hope you can get it fixed, its not too bad a job to remove that case (motor upside-down) but probably more of a task getting out of the frame as they're fairly close fitted all round.

Plenty of advice on here to help with anything you need to ask.

martin_uk:
If you dont have a parts book to see which parts split worth checking https://www.cmsnl.com/honda-cb750f2-super-sport-england_model14689/partslist/

johnm37:
Well I've finally got the engine out and split. The bad news is there's the hole in the lower casting but the top casting us also cracked in 2 places.
I took the 2 parts along with the broken bits to my welder. He tried to weld it with a variety of rods but they spat everywhere and wouldn't make a run. He was using a TIG welder and is experienced. Does anyone know what sort of rods and gas work for this? Failing that, any recommendations for someone who can weld it? I'm near Abingdon in Oxfordshire.
My final option seems to be a second hand pair of casings. I've found a new pair for sale but at £2700+ they're eye wateringly expensive.
Thanks for the tip about cmsnl. I've downloaded all of their drawings.

royhall:
Spitting like that is usually contamination, are you sure they were really clean and the black paint removed. They also need to be preheated and welded a bit at a time to avoid distortion. Give DK in Stafford a ring, they may have some good used cases for sale or try good old eBay.

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