Eliminating the Air Preload

Has anyone ever sealed the front forks on an 85 VFR500, or any of it's vintage? Most manufacturers no longer use air assisted preload because it compressable and temperature changes how it reacts. Could you seal the forks and add a small preload spacer?

Ideas?

Thanks,
Mike

 

Bump!

I know you guys are looking.

 

The forks are already sealed. The most practical way to deal with not using air pressure to preload the forks is to let all the pressure out with the bike on the centerstand to un-weight the front end. Then take the bike off the centerstand and measure the laden (or static) sag with you on the bike. At that point, you will probably have something greater than 40mm. 32-35mm is a pretty decent range for a street bike, so if you use that as a target, you will need to remove the fork tube caps, measure the preload spacers and make some that are longer by the difference in your sag measurement minus the target measurement.

So if your measured sag was 50mm and you want 32mm, your preload spacers will have to be 18mm longer than they currently are.

And after you get that worked out, provided that the basic spring rate will work for your weight, you may have to adjust the oil level height up to keep the forks from bottoming under severe diving.

Probably the reason nobody has responded is that there is a whole lotta stuff to consider and account for when you start modifying or tuning suspension. It is hard to know where to start when typing a response, and it can rapidly turn into a book...

Hope that helps!

 

.....yeah!

 

Yes, the best way to make use of the air volumn in the upper fork tubes is by adjusting the OIL LEVEL. (As said in the previous post, but I repeat that detail. It's not preload that air springs are best at (because of temperature and moisture etc) But rather progressive spring rate on compression. Again as mentioned by others, adjust the oil level UP to limit bottoming.

Too high however, and the seals will blow! Always some trade off ;-)

Cheers

CalG

 

Thanks Guys. I guess I could have been more specific too. the bike has some fancy Lockhart Phillips gauge on top of one of the fork tubes and a compression fitting type tube going from one fork cap to the other. I just rebuilt the forks with new oil and seals, but the forks won't hold air pressure according to the gauge. So to seal the forks I need new fork caps without holes in the tops of them for the gauge and transfer hose, or just plug the holes. There are no preload spacers under the fork caps on the bike either. Were there originally?

It's had a hard life.

 

Bump.

So did the bike originally have preload spacers under the fork caps? Did each individual cap have it's own schrader valve?

I can make preload spacers, but if anyone has a set of stock fork caps that could really help.

Thanks,
Mike