'56 NH350 gearbox crack
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'56 NH350 gearbox crack
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
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
1955 VH500 alloy head
1956 NH350 restoration in progress
1956 NH350 restoration in progress
- Roger Gwynn
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Re: '56 NH350 gearbox crack
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
https://draganfly.co.uk/shop/63479/kick ... /#3610-52U
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
- paul.jameson
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Re: '56 NH350 gearbox crack
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.
Paul Jameson
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
35 LG (project), 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
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Re: '56 NH350 gearbox crack
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
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
1955 VH500 alloy head
1956 NH350 restoration in progress
1956 NH350 restoration in progress
- Roger Gwynn
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Re: '56 NH350 gearbox crack
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.
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
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Re: '56 NH350 gearbox crack
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
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
1955 VH500 alloy head
1956 NH350 restoration in progress
1956 NH350 restoration in progress
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Re: '56 NH350 gearbox crack
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.
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.
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Re: '56 NH350 gearbox crack
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
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
1955 VH500 alloy head
1956 NH350 restoration in progress
1956 NH350 restoration in progress
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- Holder of a Nylon Anorak
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Re: '56 NH350 gearbox crack
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
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
1955 VH500 alloy head
1956 NH350 restoration in progress
1956 NH350 restoration in progress
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- Holder of a Nylon Anorak
- Posts: 298
- Joined: Tue Oct 05, 2021 8:25 pm
- Location: Notts, UK
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Re: '56 NH350 gearbox crack
I managed to source a filthy but sound inner gearbox case on eBay. I replaced to mainshaft bearing in the case and reassembled the gearbox. All seems well as I can select gears and use the kickstart. I bought the kickstart lever at a AGM autojumble along with a host of other items. My thanks to Geoff Brown for the mainshaft oil seal and its carrier. Thanks also to Rob Jameson for the inner primary chaincase and to Stan Coupland for the petrol tank. I am well on the way to assembling my NH 350 from parts. The frame and engine are matching numbers but there were many cycle parts missing when I bought the bike e.g. swinging arm, wheels and tanks etc.
Dennis
Dennis
1955 VH500 alloy head
1956 NH350 restoration in progress
1956 NH350 restoration in progress
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