The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: BSARoadRocket on 09.05. 2015 04:28
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Hello,
I'm planning to convert my A10 to a belt drive primary. My concern is that the common belt drive primary kits on the market don't have a cush drive on the crank or a rubber cushioning setup in the clutch hub.
I'm concerned that with out some sort of cushioning setup in the driveline I would be more likely to break things such as gears in my gearbox. I once had a tooth break off of the small layshaft gear (it was well worn/pitted and had a flaw in it) so I'm wary of any modifications that would increase my chances of breaking things.
Contrary to what a lot of people seem to think I've read that belts are pretty tough and don't have any cushioning properties to them.
SRM offers a service to modify the stock A10 cush drive on the crank to run with a belt. This seems like a very good idea...except the original cush drive needs oil and I plan to run my belt dry. SRM says that the compensator assembly will just need a squirt of chain lube (or maybe it's chain wax, I can't remember for sure) every couple thousand miles and it will be fine. I'm not fully convinced.
If anybody can share any experience with running a belt drive with no cush drive assembly I'm interested.
If anybody has experience to share concerning the SRM conversion where the stock cush drive is modified to run a belt I'm would be interested to know your experience.
Belt drive kits are expensive and my hope is to get the most trouble free reliable setup I can get my hands on.
Any experience anybody is willing to share will be most appreciated!
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The smoothest (and most powerful) of my A10's is a 1960 SR. I rebuilt (constructed) it starting with a bottom end, and frame.
I needed a clutch, so had a spare one lying around from a PE400.
I gave it to Colin Tie, and he performed the same belt drive convervion he does for his Gold Stars.
He rides his bikes frequently (and hard), and prefers the belt drive for smoothness (and no leaks).
The only cush arrangement is the belt itself.
Richard
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Hi,
I sorry I can't offer you any experience of running with a primary belt drive with out cush drive, but if it's any help I can offer that my A10 was fitted with a belt drive by a previous owner (manufacturer unknown) which still has the cush drive incorporated and I find it to run very smoothly and quietly. It has also removed any oil leakage problems as it runs dry. I don't ride hard as I respect the bike is nearly as old as me *ex*, but would guess that the racing fraternity would probably know the most about stress levels and parts breaking due to extreme use.
I'm struggling to add any pictures as it keeps saying they are over the 1000kb limit - if any one knows how to compress picture files, I'll add some later. *smiley4*
Regards,
Richard
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G'day BSARoadRocket. I'm running a belt with no cush on the cafe. It puts out a bit more grunt than the average A10. No problems, smooth, quiet and dry. Running a Commando type diaphragm clutch.
Beeza Bloke look here http://www.a7a10.net/forum/index.php?topic=427.0
I use my Outlook mail to resize.
cheers
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G'day Muskrat, thanks for the I.T. guidance, resized the pictures of my A10 primary drive belt so here they are (hopefully) on this posting.
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I run a bob newby belt conversion and cannot speak too highly of it. Nice and quiet; and I certainly am not gentle on the box with two middle aged (cough cough) blokes being lugged round while revving the snot out of it *whistle*
I do run it ventilated and dry though and have a very wide belt fitted
Doesnt seem to miss the cush drive and we do some hard starts on it, spinning up the rear and wheel standing.
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Hi, BSARoadRocket ,
The belt drives that use the Triumph/BSA three or four spring inner drum usually have the shock absorber incorporated
HTH
John
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Hello,
My Super Rocket has the full SRM belt drive, cush mod with special nut and has done 4500 miles since 2011 works great and smooth.
The maintenance is to remove primary cover every 2000 miles and squirt with chain lube I use PJ11 and works fine.
The drive take up will be harsher without the cush drive mod so if you are considering then go for the full mod don't cut corners.
Good Luck with whatever you decide.
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hi guys, recently fitted `Belt Drive Primary` courtesy of AlanP. Fitted clutch then measured up spacer for main pulley centralizing belt. Had spacer made and fitted the pulley, had to make a main shaft nut so cut off part of original nut then welded a "large nut on after drilling it out 20mm worked a treat,cheers