Author Topic: Gearbox mounting bolts  (Read 484 times)

Offline KeithA

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Gearbox mounting bolts
« on: 08.01. 2016 09:59 »
I have been researching to find out the correct bolts for mounting the gearbox to the engine on 52 star twin.
Mine has 4 bolts, (3/8W x 1 1/2") but my parts list shows 2 bolts (3/8W x 1 1/2") and 2 studs with nuts, measuring 3/8W16TPI - 3/8BSF20TPI each
I suspect that the 52/53 ST had bolts, then changed to the 2 bolts and 2 studs for the SS in 54. Is this correct??
Also if the crankcase had 2 studs, then it would be near impossible to move the gearbox out far enough to clear the studs, if the complete box was to be removed, unless of course the main shaft was taken out.
These studs are part number 35-4005 gearbox fixing stud (crankcase bottom fixing) 2 off, listed for A7, A10, and Star Twin.
This part number also listed for plunger and swing arm frame from 1954.
Any help would be greatly appreciated.
Thanks Keith

Online Greybeard

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Re: Gearbox mounting bolts
« Reply #1 on: 08.01. 2016 11:59 »
My ,55 has two studs and two bolts. Makes sense when you come to remove/refit the gearbox.

Online morris

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Re: Gearbox mounting bolts
« Reply #2 on: 08.01. 2016 21:33 »
My '47-'53 parts list also shows 2 studs and 2 bolts.
The '52 plunger came with 4 bolts though. I think most now will have the studs removed and replaced by bolts to make the removal of the box more easy. It indeed is impossible to separate engine and box even if there's only 2 studs. The main shaft has to be removed to take the box off.
But even with bolts, the box has to be tilted backwards to separate it from the engine and also tilted to bolt it back on again, so there's a lot of risk in damaging the primary case oil seal when fiddling to get the box on. In the end I went for 4 studs and took the main shaft out before mounting the box. The shaft then can be slid straight in without damaging the seal.
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
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