[Fot] bike engine oil for overdrive gearbox?

[John H. Hasty]

We used Mobile 1 SAE 5 in our TZ 250 A 1990 AMA championship bike

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On Dec 16, 2018, at 5:19 PM, van.mulders.marcel--- via Fot <fot at autox.team.net<mailto:fot at autox.team.net>> wrote:

Terry

https://www.widman.biz/mini_pics/classic-mini-oil.pdf
The adress above is an interesting article about engine/gearbox oil for classic mini's. The conclusion of the author is that it's all about the right choice : engine oils that have the shear stability for the gears do exist. I've a dogbox, so it has straight cut gears (with less sliding action I think) just like most bike gearboxes. Classic Mini's have frequently gearbox problems, maybe part of these can be avoided with the right oil. But most bikes are not particulary weak in the gearbox area, so I think it is worth looking for a right oil to try in an overdrive gearbox. My car is accelerating fast, inclusive 4th gear, but when overdrive is engaged, rpm is climbing slowly. I've mounted a 25% overdrive now instead of a 28% so far : that will make things a little better, but I'm still trying to find ways to make the overdrive less power sapping.
Marcel

________________________________
Van: "fot" <fot at autox.team.net<mailto:fot at autox.team.net>>
Aan: "fot" <fot at autox.team.net<mailto:fot at autox.team.net>>
Verzonden: Zondag 16 december 2018 19:01:54
Onderwerp: Re: [Fot] bike engine oil for overdrive gearbox?

The OD shares it’s oil with the transmission.   I’d really worry about transmission life with engine oil as it’s lubricant.  Engine oil does not have the shear stability that gear oils do.
One of the worst features of the classic Mini is the fact that it shares it’s engine oil with the gearbox.

Terry Stetler

Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10

________________________________
From: Fot <fot-bounces at autox.team.net<mailto:fot-bounces at autox.team.net>> on behalf of van.mulders.marcel--- via Fot <fot at autox.team.net<mailto:fot at autox.team.net>>
Sent: Sunday, December 16, 2018 11:08:41 AM
To: fot
Subject: [Fot] bike engine oil for overdrive gearbox?

Like most TR racers I believe that an overdrive gearbox is worth some laptime on most racetracks. But there are some drawbacks :9.5kgs weight penalty and the gap between 4th gear and 4th overdrive gear is too big. There is also a considerable amount of power loss when the overdrive is engaged because of the friction in the overdrive gears : but I think that in general modern engine oil can reduce the friction in the overdrive, compared to GL-4 gear oil, because it has much better friction modifiers. But are these friction modifiers compatible with the clutch in the overdrive?? Classic Mini's and most bikes have 1 oil pan for both engine and gearbox : what about using a modern bike oil or a modern (synthetic) classic mini oil in an overdrive gearbox to reduce the friction in the overdrive and gain some acceleration when 4th overdrive gear is engaged?
Marcel

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