Primary Chain Oil

[hendred]

Had an interesting talk at Velocette Owners Club night on Tuesday.  The subject was the Velocette clutch and primary drive.  The presenter, a very knowledgeable motor engineer, said they had stopped recommending Automatic Transmission Fluid (ATF) for use in primary chaincases.  The reason being that most available ATF has friction modifiers which reduce friction between surfaces as slip speed is reduced.  If used in a wet clutch this will cause clutch slip.  The early type ATF did not have the modifiers added.  My Silk manual gives TQF automatic transmission fluid for the primary chaincase and forks.  TQF was specified for early Ford and Borg Warner automatic gearboxes.  Castrol still make TQF atf (available from Opie Oils) and say it is suitable for motorcycle primary chaincases.  Other oil suppliers seem to list the unmodified atf as type F.  Apparently Dexron and Mercon types all have the friction modifiers. His recommendation if TQF is difficult to get is ISO 32 hydraulic oil.  Have to check which type of ATF I have in my primary.  Might get away with less spring load on the clutch if I'm using the wrong oil.

[Smokey_Paul]

Always used Silkolene light gear oil and been perfect for me.

[peter Whitwell]

I see there is various options on primary oil, Paul are you suggesting silkolene light gear oil ? Sae 75/90

Why did Silk suggest ATF when other bike manufacturers recommended std engine oil?

[Smokey_Paul]

Hi Peter

Yes absolutely that is what I use.

I think the thought was during that period transmission fluid was a popular choice for primary cases such as triumph etc due to the application type but as car gearboxes got more and more complicated so did the oil as you say in fact it changed in use type with multiple modifiers.

Silkolene developed the light gear oil to work in two stroke clutches and drives and after talking to their technical team they gave me a lot of confidence in the product. In fact I now use it in all my pre unit and similar vintage clutches.