BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: Phil C on 16 May, 2018, 13:31:15

Title: Primary chaincase oil
Post by: Phil C on 16 May, 2018, 13:31:15
Could someone advise me what oil I should use in the primary chaincase on my 1965 B40F please?   Thanks.   Phil.
Title: Re: Primary chaincase oil
Post by: AWJDThumper on 16 May, 2018, 14:33:51
It is specified as being the same as the fork oil but slightly thinner than engine oil. 10W30 would be ok but make sure it's suitable for a wet clutch engine and doesn't contain friction modifiers (moly). In more modern parlance, a JASO MA oil is ideal. A lot of people swear by ATF in the chaincase since it's also designed for wet clutches.
Title: Re: Primary chaincase oil
Post by: Dabbist on 16 May, 2018, 18:20:30
Rupert Ratio does suggest a breathing mod for B40s which results in them sharing the engine oil and primary drive oil, so one must assume that engine oil is fine.
 Thumper's right though. The oil can play havoc with the clutch. I've been through all sorts of options on trials bikes, trying to stop clutch drag. I've used both ATF and engine oil successfully. My Cub's running on a 10w40
Title: Re: Primary chaincase oil
Post by: AWJDThumper on 16 May, 2018, 20:08:21
The original spec for the B40 was SAE 30/40 (W/S) for the engine and SAE 20 for chaincase and forks. Using a thicker engine oil for the chaincase might increase the tendency of the clutch to slip but I don't think there's much in it.
Title: Re: Primary chaincase oil
Post by: Phil C on 17 May, 2018, 09:09:48
In my shed I have the following.  Are any of them suitable for the primary chaincase?

-  Silkolene Comp 4 10w-30 synthetic ester based engine oil   MA2   JASO T903:2011

-  Castrol Power 1 Racing   10w-40  4T

-  Comma Classic 20w50  API SE CC  (This is what I have in the engine.)

Or do I need to buy something else?  Thanks in advance.   Phil.

Title: Re: Primary chaincase oil
Post by: JulianS on 17 May, 2018, 09:41:21
I recently fitted an SRM 4 spring clutch to my A10. They recommended standard 10/30 or 10/40 and also recommended do not us TQF or ATF automatic transmission oil or fork oil as they contain anti friction additives which will make the clutch slip.

I used 10/40 which works fine. Have also used Morris 20/50, same as I use in the engine, and also Morris 20 and they work fine also.

ATF comes in various specifications for different vehicles and if you choose this you need to select the appropriate spec to suit or you will get slip.
Title: Re: Primary chaincase oil
Post by: Phil C on 17 May, 2018, 11:01:49
Thanks Julian. So of the three I mention, which, if any, is suitable?  Or are they all suitable?   Phil.

PS A bit complicated, isn't it?
Title: Re: Primary chaincase oil
Post by: AWJDThumper on 17 May, 2018, 11:44:43
The first two oil are fine since they are JASO MA rated and suitable for wet clutches. The third is a mineral oil but may be a bit viscous for the chaincase.
Title: Re: Primary chaincase oil
Post by: JulianS on 17 May, 2018, 14:31:19
Phil

Its not complicated but it is easy to over think the issue.

These bikes were designed for basic back yard maintenance

The only time I have experienced oil related clutch slip on my A10 was when I used an unsuitable ATF fluid.

When I run out of 10/40 I will go back to 20/50 because it is what I use in the engine and because I have not had any problems with it, just a nice light,  progressive and non slipping clutch.
Title: Re: Primary chaincase oil
Post by: hoogerbooger on 17 May, 2018, 17:55:47
have been watching with interest. I think I'll try 20/50 as that's what I have for the engine.

I presume it's just a case of if the the clutch doesn't pick up/slips  ...but seems to be adjusted correctly ... then try one of the others.
Title: Re: Primary chaincase oil
Post by: Mike40M on 10 April, 2020, 17:34:36
Waking up an old thread, though most seems to be said. Looks like the unit singles can use almost anything liquid in the primary.
I uses a lot of racing 10W-50 API SM, JASO MA2, ACEA A3 synthetic in both modern and classic race bikes.
Anybody think I can't use it in my unit singles?
Title: Re: Primary chaincase oil
Post by: Pete A10 on 10 April, 2020, 19:04:00
Why not just use what BSA recommend - SAE 20. Available on line for about£12.00/litre which will be more than enough to do the forks as well. All this information is in the User Manual which you can download for free from bsaunitsingles.com
Title: Re: Primary chaincase oil
Post by: Mike40M on 10 April, 2020, 22:46:51
Four reasons. Already using some 20 different kinds of oils. Don't want to add another one.
I prefer things I can get immediately at a local shop instead of waiting a couple of days for delivery.
For the forks I already have 5 different viscosity fork oils.
Price. I pay £3.21/litre for the oil I use in the race bikes. (Except the Manx which uses an environmentally friendly non fossil oil called R40)
Title: Re: Primary chaincase oil
Post by: DAVE BRADY on 11 April, 2020, 07:29:12
Hi,

I have used ATF in '51 Flash and '68 Thunderbolt for many years and many miles. No problems.

Dave.