'56 NH350 gearbox crack

[dennis.t]

Took my '56 NH350 gearbox apart today to find a large crack in the kickstart shaft support in the inner casing. The gearbox is a new acquisition so I do not know its history.
Is the crack repairable and should there be a bush inside the hole for the kickstart shaft to pivot on?
If there should be a bush it looks like the gearbox was assembled without one as there is no sign of a broken bush in an otherwise clean set up.
Dennis

[Roger Gwynn]

A quick check in the parts book would tell you that there should be a bush. It is certainly repairable by welding and machining, a used case would be cheaper and easier.
https://draganfly.co.uk/shop/63479/kick ... /#3610-52U

[paul.jameson]

If the gearbox is for a 56 bike, then the 54 mainshaft will be the wrong length. The different lengths are fully explained in the Drags catalogue and under Gearbox in the Ariel 4-stroke part of their website. Someone will do you a straight swop, I would expect. The GB5 gearbox is the same as the GB6 gearbox, except for the fact that it came with a 2 plate clutch for the 350 instead of a 3 plate one for the 500 / 600 / 650.

[dennis.t]

Paul,
Many thanks for your reply. I note your comments about sourcing a replacement inner case and the mainshaft length. Strangely, the gearbox was mated to the engine with the engine plates when I bought it suggesting that the engine and gearbox were used together. But, the engine number confirms it is a '56. I shall have to do further investigation into the length of the gearbox mainshaft. Is it even remotely possible that a'54 gearbox would have had a mainshaft suitable for the '56 engine fitted?
Regards,
Dennis

[Roger Gwynn]

it is very possible that someone has changed the shaft, especially if it has been used in a 1956-58 machine and the clutch has not been rubbing on the primary case. Best to measure the mainshaft as Paul suggests, the shafts are interchangeable.

[dennis.t]

Roger,
Thank you for that information. I should have credited you with suggesting buying an inner case rather than repairing mine. By chance there was one on eBay that I have purchased. As for the mainshaft, I have the dimensions from a post on this forum but it is difficult to measure the shaft in situ. When I change the inner case I will remove the gear cluster and measure the shaft and take it from there.
Dennis

[will_curry]

Dennis,

Did you find this diagram?

https://draganfly.co.uk/wp-content/uplo ... engths.jpg

It has dimensions from the outise of the box so can be used without taking the shaft out.

[dennis.t]

Will,
Thank you yes I have seen the diagram but I can't take a measurement for 'C' until I remove the sprocket retainer. I will do that at some point to replace the mainshaft oil seal.
Dennis

[dennis.t]

Will,
I looked again at the diagram you suggested and the measurement of the main-shaft from the oil seal to the drive sprocket end. I measured this as 3 and 3/8 inches or 3.375. The diagram indicates a length of 3.40 so I believe I have the longer shaft for the FERC which is correct for the '56 set up. It looks like I have been lucky! Not so lucky as I was sold the wrong, thinner, inner primary chaincase. Every day is a learning day.
Many thanks,
Dennis