Fork oil

I want to change the fork oil in my 82 Seca 750. Can somebody tell me the recommended oil weight, the quantity of oil and the air pressure required.

Thanks

Ken

 

As per our beloved Haynes (no, really guys, I love this book):
Oil: SAE 20W
Quantity: 309 cc (10.5 US fl oz)
Pressure: 0.4 kg/cm2 (5.7 psi)
Good luck!

 

I knowthe haynes calls for a fork oil SAE 20W but it seem to be a liitle bit to high. I would like to hear your opinion.

 

FORK OIL:

Unlike motor oil or gear oil, fork oil's major purpose is not lubrication.....rather, it acts as part of the suspension system, providing both damping and rebound control functions. The different "weight" or viscosity of fork oils allows you to modify the ride and handling characteristics of your bike in a fairly simple way.

And yes, it IS a lubricant also!

Although many people----including, unbelievably, Yamaha itself----recommends the use of engine motor oil as a substitute for fork oil, this is not a very good idea. Engine oils (or any multi-viscosity oil) uses additives and detergents that, while wonderful in for their intended purposes inside an engine block, tranny case, or rear drive unit, are not such a good idea inside forks. Forks operate at a much lower temperature and temperature RANGE than engine and drivetrains do, and thus do not need all those additives. And fork oil also tends to contain higher percentages of molybdenum disulfide and anti-foaming agents than engine or gear oil, both of which are very important to proper fork operation.

As a small example.......most motor oils are of a multi-viscosity nature (such as 10W30) which change their viscosity in relation to their temperature (thin when cool, thicker as they warm). A very necessary and useful feature for an engine, where you do not want your oil thinning out as the engine warms up. Not such a good idea for your suspension----unless for some reason you WANT your handling characteristics to change (get stiffer) as the forks heat up!

Also, be aware that due to different manufacturer marketing standards, that a 10W fork oil may not be the same viscosity as another manufacturers 10W fork oil, and may or may not have a direct translation to engine oil viscosities (which are standardized).

For most models, Yamaha specified the use of 10W fork oil, except for the rare occasions when they specified 10W30 motor oil. The XJ750 Seca models are an exception to this rule, as the 1981-83 models are specified as using a 20W fork oil, while the 1984 XJ750RL and all the XJ900 models are specified to use a 5W fork oil.

 

Ya think the 20W was to ensure the anti-dive worked?

 

I thought the 20w was a little harsh for the street so I went to 15w. I had the anti-dive turned all the way out so i'll probably have to turn it in some.
With all the work I did this winter I haven't gone too far. But it looks like this weekend is going to be the real shake down.
By the way I haven't used any air. As I don't have a good way to regulate such low pressure accurately.

 

This may sound dumb but does a 1982 seca 650 take fork oil?I am not seeing any simple way of adding to it or changing it.

 

I reckon my 750 had the anti dive that is why I am confused.