Author Topic: My BSA's  (Read 544 times)

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My BSA's
« on: 16 March, 2020, 15:50:34 »
!955 Gold Star with DBD head
1957 Gold Star flattracker
1957 A10 Golden Flash
1970 A65L modified with some special parts
1972 A70L Lightning 750

Which of the Morris gearbox oils do you suggest for the A65/A70 and why?

Ride safe
Morgan Johansson
BSA Bulletin Board & BritBike forum admin
« Last Edit: 16 March, 2020, 15:53:20 by BritBike »
Morgan Johansson

BSA Bulletin Board
BritBike forum
Online since 1996


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Re: My BSA's
« Reply #1 on: 16 March, 2020, 20:02:10 »
Hi Morgan,

There has been quite lot of discussion about gearbox oil with no real conclusion.  I have always used a 80/90 gear oil in my BSAs and they have covered many thousands of miles.  BSA had various recommendations over the years but did eventually specify a gear oil rather than a mono grade engine oil.  Some of the latest gear oils may not be suitable as they damage the bronze bushes so a GL4 is apparently the preferred option.
I have never used Morris oils but I have mostly used Comma 80/90 gear oil.
I believe that the specific gear oil is designed to have its molecules chopped by the action of the gears and then reform to maintain its effectiveness over a long period of hard use.
Both my wife's '51 Flash and my '68 Thunderbolt have covered well over 100,000 miles each and we also covered up to 50,000 miles on an '59 Flash with sidecar with all gearboxes remaining in good condition.
I hope this helps.



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Re: My BSA's
« Reply #2 on: 17 March, 2020, 07:19:06 »
I prefer the Motul Gear 300 Oil 75W90 GL-5, which according to the data sheet is yellow metal friendly.
Recommended by TTI for their racing gearboxes. They also recommend Castrol Syntrax 75W90 GL-5, but I haven't checked its data sheet for bushing compatibility.