R90S ATE caliper rebuild

[disston]

There were so many of those anti-dive small springs sold in the 70's and 80's that I think if you surveyed all the bikes getting rebuilt forks today you would find more with the small springs than with rubber bumpers.

Charlie

[Hawk Medicine]

Originally Posted by JonnyCash

Now would be the time to go with a handlebar mounted MC! I put one one my single ATE front end, and I swear it has more usable stopping power than when I was running the stock ATE dual disks like you are. I used a general fitment Magura MC and it looks good and works great. This being an R90S you might be wanting to keep it all stock, but it's all bolt on stuff, so you could always go back if you wanted, but I bet you never would.

Originally Posted by craydds

I might consider that master cylinder. I am not going for a show bike or a trailer queen, I want to RIDE this bike, so keeping it all original is not too important. Yes, it will still look like an R90S, but I am going with some basic upgrades - I want it to STOP!

This would indeed be a good time to swap to the HB master cyl. I did that on my bike and it makes a world of difference in brake feel. As a matter of fact, at the time I finished my bike I also owned an 83-RS and to me the ATE's, rebuilt and with SS Lines, stop as well as Brembo two-pots rebuilt and with SS lines but have better feel.

When my bike was first put back on the road, I ran dual ATE's with the under-tank set-up and that was an enormous improvement over the single thing but the HB is better, more convenient, won't puke on your frame, etc. My only advice would be to buy the entire mechanism is a complete unit and make sure that the gears are good.

Good luck.

[Mallard]

Originally Posted by disston

There were so many of those anti-dive small springs sold in the 70's and 80's that I think if you surveyed all the bikes getting rebuilt forks today you would find more with the small springs than with rubber bumpers.

Charlie

That's interesting Disston.
Were the anti-bottoming springs much of an improvement over the stock setup, or was it just good marketing and a lack of folks correctly setting their original setup, as craydds suggested?

[disston]

I only vaguely remember them. Never had a set and yet I did rebuilt several front ends for a couple of friends. It might be because the place I worked at sold parts and we did not sell these parts so maybe that's why the memory is vague just for me. I do seem to remember them. I worked at Capital Cycle for a couple of years in the early, or mid, '80's.

It does seem that now the subject comes up all the time. People are taking the bottom plugs off and rebuilding their forks and they write about these funny springs they found, which aren't on the parts fiche. I found a set in the forks I took apart a couple of weeks ago. And many others. They keep popping up all over the country.

General concensis seems to be they didn't work, were the wrong idea, there really is no problem, etc. I personally heard of one rider that liked them, forget why. There are probably others. I'm leaving them out of the forks I'm trying to fix. Think I might frame them and hang on the wall.

Somebody might know, I wonder what these cost?

Charlie

[Hawk Medicine]

Originally Posted by disston

SNIP!

General consensus seems to be they didn't work, were the wrong idea, there really is no problem, etc. I personally heard of one rider that liked them, forget why. There are probably others. I'm leaving them out of the forks I'm trying to fix. Think I might frame them and hang on the wall.

Somebody might know, I wonder what these cost?

Charlie

The 1992 Lufty price booklet lists Crossover Springs, Part #10586 list at $37.95 per set.

It's interesting that these springs are listed as "Crossover Springs" because my thoughts are that they weren't manufactured as "Anti-dive" springs but were probably/almost certainly intended to allow for a measured amount of initial, controlled dive and weight transfer, before the relatively stiff main springs come into play.

Thinking about it, the system makes perfect sense to me but in everyday application and with guys simply dropping the springs in place and expecting a significant improvement in handling, maybe not so good, as far as ideas go.

The guy here in Santa Rosa who rebuilt my R90 engine says that he uses SB Chevy valve springs in place of the Lufty parts with good success but then again, he screwed up a perfectly good engine, so I doubt that I'd trust his word again!

[craydds]

Fork alignment problems are caused by the upper clamp:


The fork tube bores on the SJ brace are closer together than the stock brace:


I ordered a new brace from Toaster.Tan

[craydds]

While waiting on parts to arrive, I'll kill some time. Got a soda blaster:


Try it out on my '76 R90S that I will be restoring for my son:


Lots of corossion:


Other projects, too:


Parts are coming together for the '75 R90S:


I have a few more things to do:


I know none of this makes any sense now. But when it all starts going together...

[Xcuvator]

Originally Posted by craydds

Fork alignment problems are caused by the upper clamp:
The fork tube bores on the SJ brace are closer together than the stock brace:

I have installed at least four SJ top clamps and each one measured right. I have found one non SJ clamp that was off by .006". Are you sure the one in question is a SJ?

[craydds]

Originally Posted by Xcuvator

Are you sure the one in question is a SJ?

Pretty sure I bought it from CC Products/SJ BMW. But, that was many years ago, probably early-to-mid eighties.

[craydds]

Things are moving slowly. Just doing little tasks like cleaning and repacking wheel bearings, steering head bearings, etc. Nothing too exciting, not worth making pictures. blah...

[Mallard]

1) I just did a handlebar master cylinder conversion on my R90/6.
The brake switch you have there (picture in post #52) looks like the correct switch for that nice new master cylinder / throttle assembly you have there too. Will you just cut off the 'new' brake switch connecting pin and add some spade connectors or modify the spade connectors that use to connect to the under-tank master cylinder, to match with the 'new' brake switch connector? I'm using the first option (thanks to my very competent supplier rather than my good planning).

- Clear as mud, unless you sort of know what I mean guess.

2) The thread being called "ATE caliper rebuild" and all, did you ever read anything about removing the caliper piston without the use of compressed air? Is there a way to remove it without such a blast? I'm just about to try pumping the brake with the pads removed to see what happens (a big mess and a loose piston I'm hoping).

[craydds]

1. I think I'll go with something easy, like spade connectors or posilocks, to connect to the brake light wires. If I could find the connector that matches the new brake light switch, maybe Radioshack (?), then I might solder that into place.

2. I'll bet that removing the pads, then pumping the brake - keeping reservoir topped off - could work; might be a slower and more gentle way to remove the pistons. Give it a try - it can't hurt anything. Good way to flush the brake system. I removed the calipers from the fork sliders, then used compressed air to pop the pistons out.

[knary]

Originally Posted by Mallard

2) The thread being called "ATE caliper rebuild" and all, did you ever read anything about removing the caliper piston without the use of compressed air? Is there a way to remove it without such a blast? I'm just about to try pumping the brake with the pads removed to see what happens (a big mess and a loose piston I'm hoping).

If you're ok with a little clean up, I recently found that the grease gun trick worked very well and without turning the piston into a projectile.

Unscrew the brake line. Screw in the end of a grease gun. Pump away until the piston pops out. You will end up with some grease to clean up, but it isn't much of a mess.

[surtees]

Nice to see several of us are at about the same stage of this. On my r90/6 being converted to dual disk,I have test fitted the new handle bar MC and it fits but with little room to spare. I have about 3/4" for the banjo bolt between where the brake line attaches and the tach (left yellow arrow) and I can just fit the reservoir under my S faring (right arrow). I have seen some models with a notch cut from the faring but I am reluctant to do this.


I do have a couple of questions if anyone can help.
1. I was planning on maybe doing a double banjo and going direct to the calipers but probably not enough room for that. Am I correct in this? I am not sure of the size of the double banjo or if it is even a good idea to do it that way.
2. So I will probably need go the route of a under the tank distribution piece. I don't have the distribution block yet but also getting ready to order the new lines. Does anyone know the specifics of the fittings for the handle bar banjo bolt, and the fittings that go into the distribution block (are they the same as the under tank MC fittings?).
3. I measured the lengths for the MC to under tank distribution as 13.5"; and from the under tank to the fork brake pipes as 20" but would be grateful for any confirmation or input.
4. I also purchased a new brake switch but if I go with the under tank distribution I am not sure the advantage of using it vs just attaching it to the distribution block, is there one?

thanks all and happy holidays.
surtees

[craydds]

Originally Posted by surtees

1. I was planning on maybe doing a double banjo and going direct to the calipers but probably not enough room for that. Am I correct in this? I am not sure of the size of the double banjo or if it is even a good idea to do it that way.
2. So I will probably need go the route of a under the tank distribution piece. I don't have the distribution block yet but also getting ready to order the new lines. Does anyone know the specifics of the fittings for the handle bar banjo bolt, and the fittings that go into the distribution block (are they the same as the under tank MC fittings?).
3. I measured the lengths for the MC to under tank distribution as 13.5"; and from the under tank to the fork brake pipes as 20" but would be grateful for any confirmation or input.
4. I also purchased a new brake switch but if I go with the under tank distribution I am not sure the advantage of using it vs just attaching it to the distribution block, is there one?

thanks all and happy holidays.
surtees

1. If you have room for the double banjo, do two lines directly to the calipers. If room for only one banjo, why not go with one line down to one caliper, then one line from that caliper over to the other. Go look at a new sport bike.
2. The distribution block fittings are the same as the stock under-tank MC. The handle bar MC uses 10 x 1.0 banjo bolt.
3. Make sure you measure lines to calipers with forks fully extended, bike on center stand. Otherwise, there is room for variation in brake-line lengths, not too critical. A tad longer is better than too short.
4. No advantage to either switch. Switch on distribution block is easier, wires up directly to stock connections. Handle bar MC switch works well, just have to wire it in, easy connection.