Just bought my first trials bike - a 2011 Sherco 250.

As you do with a new purchase, I've leafed through the paperwork and come across some contradictions.

So the bike was serviced at John Lee's last November and they put 75W in the gearbox.

At the back of the manual, in the spec. section, it recommends 10W-40. 

In the text of the manual where they explain the location of the drain plug, they recommend 10W-50... 

Maybe it's a bit like crop rotation - a different one each time you change it...? 

Ooo Aarr!!! Crop rotation works on me mangle worzles luvley! 

75W trans oil is not wrong but you may get clutch drag as the oil is quite thick. 10w/40 is a multi grade engine oil, it will work in a bike gearbox no probs, it’s just that the gearbox may sound a little noisier, thinner oil. Some run ATF and this too will be ok but again more noise, but a better clutch operation. If the manufacturer can’t decide and it’s in print, then it’s anyone guess??

Gear oil and engine oil measure viscosity differently... an SAE 80 gearbox oil is roughly equivalent in viscosity to an SAE 20 engine oil.  An SAE 90 gearbox oil is roughly the same viscosity as an SAE 50 engine oil. 

 

75w gear oil is commonly run in trials bikes. 

Edited April 24, 20188 yr by heffergm

2 hours ago, heffergm said:

Gear oil and engine oil measure viscosity differently... an SAE 80 gearbox oil is roughly equivalent in viscosity to an SAE 20 engine oil.  An SAE 90 gearbox oil is roughly the same viscosity as an SAE 50 engine oil. 

 

Edited April 23, 20188 yr by section swept
Withdrawn

Hi Vinnie, 75W is a winter 75 grade of oil, which has a low viscosity, it is not a high viscosity oil like EP90 for example. The 75W is fine for your bike, another fine oil to use is a much less expensive ATF oil rated to Dexron III, which I have used for well over  25 years on all sorts of trial bikes. Bye, Peter B.