Good Heart, Bad Intentions: another build thread

I must have 8 hrs into filing the new triple-clamps smooth during the past week.... They started out nasty and rough:



I'm trying to get them to a nice smooth shape, and I'm liking where it's all going. Offered up to the steering neck, the lower triple is looking good, but there's a couple of problems with the fit:



There's this downward-projecting pin behind the lower bearing shell that hits the pinchbolts. I'm guessing it's something to accommodate a (nonexistent) friction-type steering damper? No matter, it's simple enough to chop. The other problem is that the TT500 steering stops face backwards. Their ramped front faces do contact the stock steering stop on the neck, but it's far from ideal. Time to flip the frame over and get quick'n'dirty:



They're the shortest 5/16" capscrews I could find on short notice. I would have preferred using the black-oxide fine-thread ones I also bought, but I couldn't find my fine taps anywheres, so I went with these SS coarse ones. Plenty of red loctite, and they're good to go.



The flat back faces of the TT500 stops touch hit the heads of the capscrews just before the sloped front faces touch the stop on the front of the neck. The pinchbolt area clears the tops of the capscrews with margin for adjustment.

Started machining the triple-clamps today. The cutting itself goes pretty quickly, but it's the fixturing and setup that seems to take forever! Anyways, the TT500 clamps are bored for 36mm tubes, and I need 38mm for the FZR600 tubes. The first step is to clamp the split bores in a fixed position as close to round as possible:



I stacked a few pieces of copper shim stock into the slots, torqued, and re-measured until I had things fairly even. Shouldn't matter if the copper is a little proud, as it will cut away just fine.

First up, the top clamp. The bottom of the TT500 top clamp has a nice machined flat to register off of, so leveling is just a matter of clamping to the table. The aluminium plates are to protect the cutter from over-travelling into the table.



The real work is dialing in the machine to the exact center of each bore, and maintaining a perfect center-to-center distance for both upper and lower clamps. Of course, these are used vintage motocross parts, so you have to make a few allowances! The stock bores were out of round almost 0.030".



Measure, measure, and measure again, do the math, then flip the switch and watch the metal fly! That first cut is always a little nerve-wracking for me. We took a succession of 0.010" passes up to 1.486", then a pair of 0.005" cleaning passes. Brought the machine back to the zero position over the center of the other bore, and bored to match.The fit is completely awesome!



You can see that we threaded a couple 8mm studs up into existing holes under the triple; these were adjusted to help support and level the piece under the clamping force.

Ran out of time today, but did manage to get the lower triple jigged and clamped in place. The lower has four existing 6mm threaded through-holes, into which we threaded four bolts to support and level the piece.



I got super lucky and needed very little adjustment to get the bores to vertical. Still had to dick around for 45min getting the machine set to the centers, but everything is clamped, locked, and dialed-in to get at it tomorrow morning!

A heap of thanks to Teak Ackman at Seven Star Marine Engineering in Newport RI for helping me sort all this out!

Things are starting to pick up speed again! First up, the steerer/quill is finished:



With the quill and triple-clamp back together (and thus the inside-to-inside axle width fixed), I could get onto fitting the axle. I'm using the stock XS650 front axle as a starting point. The FZR600 axle is the wrong width for the triple-tree width, and I was having a very hard time finding a suitable set of 15x47x14mm wheel bearing to use. By going with the stock XS axle, I can use common 17x47x14mm bearings in the stock hubs. Besides, the 17mm axle is just plain beefier, right?

To drill out the FZR600 fork lowers for the larger XS axle, I first started with the left leg. The inside faces of both fork legs are square to the axle, so that's what we registered off of. The left leg is only getting bored partway through; I'm saving the threaded portion.



The fork lower is shimmed square and level with the factory-milled face dead-flat against a machinist's block, then clamped and milled.





With a precise parallel face milled, the leg is flipped over, registered against a shimmed block, clamped, and bored. I used a 17mm straight ream; kinda a hefty cut for a 15mm hole, but it's only aluminium, and I went slow Went down 0.960", just shy of the threads.
Just a lucky coincidence I guess... the male threads on both the 15mm and 17mm axles are identical. Here's the XS axle threaded fully into the FZR600 leg, with the FZR axle for comparison:



Boring the right leg out is a little simpler, as the hole goes right through, and both faces are already factory-milled square and parallel. The split clamp is shimmed and clamped (as with the triple-clamp bores), set level, clamped, and bored through.



So there it is: a 17mm XS650 front axle in FZR600 fork lowers...



Obviously, the "head" of the stock XS axle is too long, and gets turned down and "shortened" to just shy of the cross-hole. More pics to follow!

Very nice work.

Now that I have the fork back together, I thought I'd mount the wheels and mock the suspension at my proposed final ride height...



I was hoping to have this moment of "Wow, it's really coming together!", but instead all I felt was, "Whoa... still so much to do...". Whew, time to take an afternoon off, I think.

Looking great! 'Offered up'... 'proud of the bore'... 'quill'. You a Brit by chance?

1974jh5 said:

Looking great! 'Offered up'... 'proud of the bore'... 'quill'. You a Brit by chance?

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American by birth, Canadian by upbringing, West-coast native, East-coast resident... I once caught myself saying, "That's wicked bitchin', eh?"
Turns of phrase such as "offered up" and "proud of the bore" are vestiges of a career in traditional wooden yacht construction. What I'm not is a machinist; I'm totally making all that up as I go...

Not too much to report lately, but still pluggin' along... Mainly just trying to pay for it all! Did get my new tires, and mount them up:



I'm starting to get glimpses into how the overall project will come together. I've always had a certain image in my mind, one that doesn't fall into an easily-defined category (ie., bobber, chopper, cafe, tracker, etc.). The wheel/tire combo is helping to solidify the image though...

Bitchin improv Brother .Totally makin it up as you go is how I do it to Likein this build

What kind of tires are you running?

CoastsideXS650 said:

What kind of tires are you running?

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100/90-19 Avon Roadriders

Oooh baby, hit a milestone today! Started out with getting the upper shock mount welded in. I slid into my friend's shop and managed to get the welding done between production jobs. First, a quick tack:



Then it's fully TIG-welded and back to my own shop for wire-brushing, sanding, and speed-holes:



The upper mount has a little adjustment built-in to it, but I basically set it up so that the shock is at full extension (full droop) with the rocker link as far down as possible without any binding or clearance issues. This way, the internal shock top-out will control maximum extension, not some external bump-stop or parts grinding together.

With full shock extension set, full swingarm droop is set. Again, I drop the swingarm down as low as possible without anything binding/touching. My figurin' and arithmaticin' must have been okay, as the swingarm tops out about 1-1/4" below my desired ride-height.

The link-plates are measured, cut, and drilled. The upper ends are drilled to accept 3/8" hard-chromed pins; these pins will be welded to the plates inboard, then cut and threaded for thin nuts outboard. The pins ride on 1/2" bronze bushings in the swingarm. The lower end of the link-plates is drilled to 12mm to accept the bolt through the rocker link.







Everything is still loose here, just checking for critical clearance issues, binding, etc. So far, so good! The shock body clears the swingarm by a minimum 1/8" through the travel. The tire clears the spring by a minimum 5/16" with the axle fully forward in the adjusters (I always assumed I'd have to run it a tick back for clearance).

And the milestone! She's on her own two feet again! Still loads to do, then tear-down for paint, but she feels like a bike again, not just a loose pile on the bench. Speaking of that bench, it's time for a cleaning...



...and yeah, I admit it: I popped my old handlebars on upside-down, put a board on the back tire for a seat, and sat there revving the engine for awhile...

Feels really good, don't it?

awesome rear suspension but I have a question. Those link plates you are using from the swing arm to the rocker link, the point where they attach at the rocker link looks like it'd be difficult to transfer the movement of the swingarm to the compression of the shock. you know what I'm saying?

shouldn't the links attach closer to the bottom of the shock instead of 1.5" in front of it?

KentMoney said:

awesome rear suspension but I have a question. Those link plates you are using from the swing arm to the rocker link, the point where they attach at the rocker link looks like it'd be difficult to transfer the movement of the swingarm to the compression of the shock. you know what I'm saying?

shouldn't the links attach closer to the bottom of the shock instead of 1.5" in front of it?

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The links are attached forward of the lower shock mount exactly because they make it more "difficult". The geometry decreases the leverage the swingarm has on the shock, or to put it another way, increases the leverage that the shock has on the swingarm. That, and a progressive rising-rate, is the reason for all the complication.

Back up on the bench after a little cleaning/organizing... It's nice to have gotten through a machining/building phase and be back in a design phase for awhile! Just playing with seat and rearset positioning now:



I have visual design some ideas I'd like to adhere to, but of course I still have to be able to ride the thing without undue pain! I foresee plenty of cardboard mock-ups in the coming days...

ah, I gotcha! sounds good.

Great work as usual!

That's really looking good.

Perfect so far. EXACTLY where I would like to be at that point in the build. Curious to see how you finish up, but so far PERFECT.