Gearbox Oil

[Hendred]

We had a very interesting talk by a motorcycle engine/gearbox designer and repairer at our recent VOC meeting.  We got on to the topic of gearbox oils suitable for Velocette gearboxes.  His recommendation was MTF94 which was developed for Landover and some Rover model gearboxes.  The problem with EP80/90 oils is that some contain additives which attack the yellow metals in the gearbox which results in their rapid wear.   It is difficult to tell which ones have the additives as it isn't shown on the label.  Most commonly available EP80/90 oils are just labelled API GL4 or GL5.  There is an earlier thread in this forum which mentioned Silkolene BOA or Gear Oil Medium, both of which are API GL4/5 compliant but no information on additives.

As the Silk gearbox is based on the Velocette box and contains yellow metal bushes and selector arms I will be changing over to MTF94 as the possibility of accelerated wear from EP additives has concerned me for some time.

Be interesting to hear other views on this topic and experiences of yellow metal wear - if any.

[Hendred]

Just received an email from the engine/gearbox designer.  Aparently they had designed a five speed gearbox for Silk and had just got to the prototype stage when Silk stopped production.  He also has the drawings for the gearbox.  Always something new to discover about Silks.

[Smokey_Paul]

I see on eBay there is a fully synthetic version which are you planning to use?

Please report back your findings I may follow suit after seeing many gearboxes with wear.

[Smokey_Paul]

Mind you I have been using BOA for some time after some discussion with Silkolene

[Hendred]

I'm going to go with the mineral oil.  Let you know how I get on.

[peter Whitwell]

Send me that New 5 speed box Please

[Hendred]

Rare than hen's teeth.  Never got passed the prototype stage unfortunately.

[Smokey_Paul]

I am now trying MTF94 but also having my seat recovered and petrol tank repainted etc. So expect wear to be minimal at present...

[sictransit]

Anyone have actual experience yet, or further thoughts on going to MTF94 in the gearbox, including the option of synthetic?  
Any particular brand recommended?
Currently I am de-mothballing the Mk2 and doing some minor tweaks, and this change seems to make good sense.
Tom

[Smokey_Paul]

Still running MTF94 with no issues that I know of

[Keepin' on]

Is MTF94 still the favoured gearbox oil? On-line I see Granville and Land Rover offered?

[Smokey_Paul]

All I use in the gearbox now, silkolene light gear oil in primary and comp 2 silkolene injector in 2 stroke.

[Nick]

The light gear oil is listed as 10-40 when Silk recommended 20-50 and the manual that Clive Woral gave me say straight 50 was even better?

[Keepin' on]

I’ve just taken delivery of 1L Gear Oil Light from Opie. On the large label on front of the bottle, alongside a graphic of gear wheels,  it says “SAE 75 SAE 80”. In the small print on the back of the bottle it says “For use in 2T and other separate gearbox machines. CRANKCASE RATING [emphasis added] SAE 10W - 40.” Does this perhaps indicate only different viscosity at the higher temperature of a crankcase?

[Smokey_Paul]

OK it's quite simple it's all about equivalent oils for different applications.
In a gearbox this light gear oil is equivalent to the SAE 75 / 80 so if you wanted to use in a gearbox only this is what matters.

In our case we use it in the primary case for the clutch and primary chain so the 10w40 equivalent matters here.
The difference in using this to standard 10w40 and the advantage of the light gear oil is the addition of the friction modifiers to help with clutch slip reduction and reliability.

I spent quite a time with Silkolene technical about this and have to say I use this a lot now I primary cares especially now TQF is changing so much with new car auto boxes as they now add additives to aid slip not reduce it.

[Nick]

Thanks for all the feedback, I have hardly used the bike as the handbook is not very comprehensive.
I did join the Scott owners club and Clive Worril was very helpful, but have toyed with just selling.


Also ordered some from Opie,

On changing it seems lighter than what came out, but I bought the bike from an Auction a few years ago so have no idea what was in.
Modern oils work much better these days will see how it sounds and feels when riding and will defiantly use for primary chain case.

Will give feedback

[hendred]

I don't know what handbook Clive gave you, the handbooks supplied with bikes are available on this site under downloads.

https://www.silk-motorcycles.org/downloads.html

As the bikes are over 40 years old some of the recommended parts are obsolete, such as spark plugs, or better modern lubricants are available.

Hope this helps and you get out and enjoy your Silk.

[Nick]

Thanks am working my way through them. although the exhaust one doesn't help much.
You mention spark plugs what type and rating is now best?

[hendred]

A good question and you will probably get several answers.  There is a thread on spark plugs further down this page.  NGK B8HS  work ok for some people but may foul if not ridden hard enough or the oiling system is giving too much. In this case NGK B7HS would be a better choice.  There is a theoretical advantage using a projected nose plug and I have been running NGK BP8HS for some time now with good results.  There is plenty of clearance between the plug earth electrode and the piston crown.
Whatever you decide always carry a spare set with you - it's a 2 stroke!

[Smokey_Paul]

Just use B7HS they seem OK to me, you mention exhaust where did that come from ???