Author Topic: Can you run a open primary?  (Read 1622 times)

Offline mario medeiros

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Can you run a open primary?
« on: 19.02. 2014 12:48 »
Building a a10 bobber and was wanted to see if it is possible to run a open primary (no inner or outer cover)? I know that I will have to lube the chain but other than that is there any issues I should know 1st?Thanks

Online bsa-bill

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Re: Can you run a open primary?
« Reply #1 on: 19.02. 2014 13:00 »
Apart from trouser legs  *smiley4*,  Chain issues, it spins quite fast, lube would have to be good, others that have tried it will respond I'm sure.
Best option would be a belt drive
All the best - Bill
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Offline a10gf

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Re: Can you run a open primary?
« Reply #2 on: 19.02. 2014 13:07 »
Always wondered, cush drive and rollers behind clutch would need some lubrication?

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Offline mario medeiros

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Re: Can you run a open primary?
« Reply #3 on: 19.02. 2014 15:15 »
BTW want to keep It chain drive don't want to go to a belt.Thanks

Offline alanp

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Re: Can you run a open primary?
« Reply #4 on: 19.02. 2014 16:24 »
...... rollers behind clutch would need some lubrication?

Spot on there a10gf.
How to wreck your clutch centre bearing and associated parts?......Run the primary without oil.......Even with a belt drive primary you will only get away with it with a specially designed clutch like Bob Newby Racing's belt drive assembly which is designed to run with a dry primary unlike one I won't mention.
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Offline chaterlea25

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Re: Can you run a open primary?
« Reply #5 on: 19.02. 2014 20:11 »
Hi Mario,
If its going to be a "show" bike then maybe !
If you intend to ride the bike regularly then its a BAD idea  *ex*
All the points mentioned are very valid, Another is do you value your fingers and toes ??
An open unlubed chain will heat and fail rapidly, then whats there to catch the flying metal ??  you *eek*

Bikes that had open primary chains always had a drip oiler or similar lube setups, very messy for bike and rider

My 2.5 cents worth
John



1961 Super Rocket
1963 RGS (ongoing)

Offline Briz

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Re: Can you run a open primary?
« Reply #6 on: 19.02. 2014 22:48 »
I agree. All show & no go if you ask me. If you're building a bike to use its a bad idea.
I once had to work on my clutch on a weekend ride out about 100 miles away. Had to run it dry going home. By the time I was back the chain was almost seized solid. And that was without any crud getting in there.
So you might have to lube it quite a lot!

Online Topdad

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Re: Can you run a open primary?
« Reply #7 on: 20.02. 2014 14:52 »
This is one admission that pains me and I don't like making but I did this for about 2 weeks on my first plunger A10  and can concur with all the don'ts already listed , I still had an inner and oiled the clutch bearing each day and never went any real distance but it was so messy and potentially dangerous , took chucks out of my boots. I was lucky ( and in my defence only a bulletproof ( read stupid ) 16 yrs old ) and  would say don't go there ,regards BobH.
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Online muskrat

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Re: Can you run a open primary?
« Reply #8 on: 20.02. 2014 19:18 »
I had an open chain driven 4 spring primary on my A7SS racer. A quick squirt of oil at each start up. Very rarely would it be running (read racing) for more than 15 minutes at a time. I'd get 1 or 2 meetings (5 to 10 races @ 15 miles ea) out of a chain and rollers.
It's still open but with a belt and sealed bearing for road use.
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Online KiwiGF

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Re: Can you run a open primary?
« Reply #9 on: 20.02. 2014 22:40 »
I agree with all the posts above but if you were still keen maybe an O ring chain with one of the "dry" lubricants would help with chain issues, maybe could use a dry lube on the shock absorber as well, but I cant think of how (say) the clutch bearing bearing could be made "sealed" but maybe there is a way....
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Offline Rocket Racer

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Re: Can you run a open primary?
« Reply #10 on: 21.02. 2014 01:51 »
Unless you run an o'ring it will throw dry in no time and not be efficient (the driving speed is far higher than the final drive) . An o'ring with lube would be the way to make it work.
I run a cut out back primary cover and an outer that had been chopped, so have also slotted. Until I went belt, found the dry (non oring) primary made the bike sound horrible. Whereas on an earlier norton ran o'rings as dry primary for several years.
Belts are much quieter, but a chain can be done.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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