anti dive vrs standard forks

I am doing a full restoration on a 1984 XJ750 RL. I have a set of anti dive forks from a 1983 900 that I was thinking of using, mainly because of the ease of adding air to the forks through the single line conecting the two together and because they look kind of trick. Before I go ahead and buy the seals to rebuild them I would like to get some input from people that have had experience with these forks. Are they more trouble than they are worth? I noticed they were dropped after a few years.

 

They were hardly a niche item. Kawasaki, Suzuki, even Harley used anti-dive forks on many models from the late '70's to the mid '80's. Both my '82 SECA 750 and my '83 GPz 750 have anti-dive forks. I also woudn't say they're much trouble.

You need to be a bit more careful when replacing seals in them, though, as some of the parts are unavailable, and the parts diagrams aren't very accurate. In particular, make sure not to compress the tube all the way when trying to pull the tube and boss out of the stanchion (there are small parts in the bottom that can be broken by compressing the tube fully after the bottom bolt has been undone.) Also be careful not to lose the two tiny washers that are part of the oil lock assembly.

 

Had them on my old 650 Katana...seems like a good idea on principle...I wonder why they have dissappeared?

 

I’m going to guess it was an un-sprung weight issue, or just a weight issue.

ab

 

if you look here there's a lot of anti dive forks, but no mention of yamaha :?
my guess is they went away because of $

 

I'd say anti-dive as done on my bikes only adds sprung weight (extra parts in and on the bottom of the stanchion).

Most modern forks have fixed stanchions and sprung tubes (upside-down relative to our forks). I'm not sure why, though. The stanchions are aluminum, the tubes are steel, so flipping them around I would have expected to be about a wash wrt sprung weight.

 

I think you got your sprung Unsprung reversed.

http://en.wikipedia.org/wiki/Unsprung_mass

http://en.wikipedia.org/wiki/Sprung_mass

Unless you've put inverted forks on?

ab

 

No, you're right, I did have them reversed.

If the weight of the anti-dive really was enough to be a concern, though, then that could be a reason for inverting the forks, as it would allow you to move the weight to the sprung side... assuming you could make anti-dive work with the oil lock up top even though the oil would want to go to the bottom.

 

Glenn, here's a link i just read.
My bike is fitted with them too, i am going to the trouble to rebuild them so i better make sure they are in top working condition. I read somewhere that they make your brake lever feel spongy.
As the guy said, love em or hate em.
I'm yet to get them on the bike and it's been dramas already.

 

Rockerto: Thanks for the link. I see you are working on a police special, how about posting some photos sometime.
Cheers
Glenn

 

Sure Glenn, if you search the forums author 'rockerto' you will find some posts, but i keep all the large photos of the police special build here.

Ta, Rob.

 

As i understand it and from what i've read, the adjustable anti dive system on the front and the adjustable dampening on the rear shocks, was ditched after the XJ 900rk as Yamaha copped allot of bad reviews due to the complexity of the suspention setup (remeber it was 1983). They also Scored bad reviews on the handle bar mounted fairing, hence why that disapeared too and they went to frame mounted in 1984.

I have two XJ900RK's and neither have a "spongy" brake. One of mine has braided brake lines and it pulls up like its hit a brick wall. It will wag the arse no worries.

Just make sure you rebuild the anti dive when you rebuild the shocks. The anti dive is prone to leak oil out the breather hole. They are not hand to strip, just the two allen keys that holed them to the fork legs then the two on top that hold the piston in. Strip them all apart and replace the o-rings and you will be fine.

 

Thanks for the info and advice Flash- just waiting on my forks to come back from Radhardchroming in Brisbane..

Soon it will be on two wheels. soon, soon.

 

Not a prob