My 1975 Extended Fork Dilemma

[Dave Walters]

To start I received a free 1975 front end from a friend. It was pretty ratty but I was going to be polishing the upper tree, painting the lower, Shaving and polishing lowers, and also buying extended fork tubes.

Next I found myself a set of fork tubes on ebay that were 8 over and 34mm and for a Yamaha. Paid $57 with shipping. Problem was I wanted to run 6 over.

I pulled my forks apart and started cleaning up my fork lowers.

Now I went and machined the spacers and lowering stuff I needed to lower my forks 2 inches so I would be running 6 over. My '75 front had the weird longer spacers so when I was cutting my tube to extend I just made it longer so I didnt have to put this spacer back in.

Now onto my fork dilemma:
I am sure these are the right fork tubes because the stock cap is threaded properly.

But the lower spring and parts that are clipped into the bottom of the tube do not fit right. They are very loose.
I am going to end up machining sleeves to make them fit.

I also noticed the smallest ID of the fork tube is bigger than the stock tubes. So to keep the spring from moving I might have to machine new pieces that go on the end of the springs to keep them centered. Now I am a slight bit worried that with the neck raked and the forks being 6 over that the thinner wall on these will not be as strong. When I have the front end on I will see how it feels and see if its rigid.

 

[Dave Walters]

Quick question. I am sure these forks are off a 1975 xs650b beacuse of the caliper mount tabs. The xs650c model has them different. Do the internals seem right for the 75b model?

Where on this parts diagram do you find these pieces?

Those are the pieces that are snap ringed into the bottom of the fork tube. I am not sure what their purpose is.

 

[5twins]

They are not all shown on the parts diagram, just the large collar (#8) and the snap ring (#7). They retain the damper rod in the tube, may have some effect on dampening action as well with that spring-loaded "valve" in there. Here's the same set-up out of the bottom of a '77 tube. '78 and later tubes had these parts crimped in place .....

 

[Dave Walters]

I wonder if there was a 34mm fork model that had the proper lower internals that fit in these forks tubes with out having to machine some sleeves.

Basically the dimensions of the xs650 ones I have are 26mm OD and the extended ones are 28mm.


Right here in this technical bulletin it says there was a design change to part #7 and then the OD of the circlip in part #7 was changed.