Good Heart, Bad Intentions: another build thread

The capacitor bank has been on the back burner for awhile, but I did get a little further on it this week. Had been puzzling on a way to get a wire led out of the housing in a safe and neat way, and after reading through an inch of the McMaster-Carr catalog, I found this little rascal:



Mcmaster-Carr P/N 8183K6, high-temp waterproof miniature cord grip.





The retaining nut fits perfectly into the recess inside the starter end-bell; no wrench required to hold it!



The strain-relief should be the perfect size for a single 10-Ga or maybe 8-Ga cloth-covered positive wire. The negative lead can be terminated internally, since the housing is bolted directly to the engine case.
Not quite as much fun as getting the chassis rolling, but these little details are still fun to get right.

damn! def like this...

Fussing with brakes today... The front end is coming together ever-so-slowly. First attempt at mounting the calipers had them buried into the spokes. I milled 4mm off the the outside face of each of the caliper mounting bosses (the most I felt I could safely get away with) and tried again. The spokes still wanted to rub, so I painted some layout fluid onto the calipers to check.... Just barely touching, but any amount is too much!
The wheel still needed to be perfectly centered, so with a speedometer eliminator from Hugh and a couple of 16mm hardened machine washers and shims, I centered the wheel and got this:



The spokes are still too close, but not actually touching. You can just make out the silver spot in the red layout fluid where the spokes made contact before final centering. I'd like to shave the calipers a touch, and believe that there is meat enough for safety, but will cut a spare caliper body in half forst to double-check how much actual wall thickness I have to work with.

Then onto the brakes... There's no getting around it; I need some hefty rotor offset! The FZR600 caliper bolt pattern and hub diameter is the same as the stock XS hub, but the offset is all wrong in this application. Spacers shouldn't be too hard to machine, but the measuring is annoying and fussy.



Just to get myself "in the ballpark", I shimmed the rotor out using three metric bolts with ~13mm heads. These particular bolts measured out at ~12.50mm, and the rotor isn't yet centered in the caliper slot. I'm guessing that moving the rotor out half it's own thickness will be close enough... I'm calling this spacer at 15mm.
Funny thing: I repeated this procedure twice for both sides, and arrived at a 13mm spacer for the left side, and a 15mm for the right. The wheel is freshly-trued, and measures centered between the fork tubes. The fork tubes measure parallel, so... does the XS hub have a bit of asymmetry going on (besides the obvious differences due to the speedo-drive recess)? I'm going to try not to let that 2mm difference bug me...

Out back, I'm not as far along with the spacing and mounting problems, but at least I've finally settled on a caliper and hanger:



This is no way nearly as simple and easy as Omar's rear brake hanger, but so much cooler... now to do something about the color!

Do you really have to cut a caliper in half to determine the wall thickness? Can't you just measure it? What am I missing here?

Travis said:

Do you really have to cut a caliper in half to determine the wall thickness? Can't you just measure it? What am I missing here?

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Well, I suppose I don't have to section a caliper, but... an accurate measurement would require a tool I don't have, while I do have four "extra" caliper body halves and a fresh blade in the bandsaw.

Jeez. You can't use a common ol' micrometer? Before chopping up a caliper body, I'd use a 1-2" micrometer and use the 1" 'set' as a spacer between the body and the anvil. Might be off 3-4 thou that way, or is that not accurate enough?

But man it's looking good!

can't you make something work with a spacer of some kind then measure the spacer and subtract it from your total measurement? What wall thickness are you trying to measure? The part that is just touching the spokes?

Edit: 1974jh5 beat me to it!

I'd like to measure the thickness of the brake caliper body right at the intersection of the floor and wall of the piston bores, at an angle perpendicular to that of the spokes (approx 45 degrees to the piston bores). I'll try some other spacers this weekend with my digital calipers, but I was having a hard time getting repeatable results with the materials I had at hand.
I wouldn't be so quick to cut a cross-section, except that I have a box of extra dead caliper bodies anyways, so...

Well shit, if they're dead.. go for it! I thought these were good spares.

Look at what I made today... A whole garbage can full of shavings!



But seriously, today I finally got around to getting the front brake disc spacers machined. I started with a 3" chunk of 4" aluminium round bar from McMaster-Carr. The stock is chucked the lathe, centered, faced, and turned down to 3.950" OD.



A center, pilot, and 1" hole are drilled in succession, then a few passes with a small boring bar to open up the middle...



Then the large boring bar is jigged up and the big chips/shards/shreds start to fly. The ID is opened up to 2.520", 0.025" at a time...



A parting bit cuts off the first of the two spacers, and the piece is re-faced...



I used the right-side spacer from my Omar's rear conversion kit as a template to transfer punch the hole pattern onto the new spacers. Here is Omar's piece, the TX750 hub cover, and one of the new spacers:



With the holes transferred and punched, I started with a stepped pilot, then drilled through with a 21/64" bit.



And there they are, all edges and holes given a light chamfer, ready to go. Plenty of leftover material too!



I'm still tempted to bore some additional larger holes between the bolt-holes for additional lightening, but I ran out of time at the shop. And, yeah, probably overkill.

Overkill maybe, but beautiful work.

I had also been thinking of ribbing/grooving the outside edge of these spacers... But the whole "dual 4-piston big brakes" thing is already so definitely unnecessarily over the top, I have to stop somewhere!

osteoderm said:

I had also been thinking of ribbing/grooving the outside edge of these spacers... But the whole "dual 4-piston big brakes" thing is already so definitely unnecessarily over the top, I have to stop somewhere!

Click to expand...

You do? Nobody told me that!

im not going to say im jealous of this build but i really would rather this be mine...

I AM going to say I am jealous of this build!

Now I gotta ask, what about the "centering flange" for the rotors on the spacers? The stock location and the Omar's kit have a flange that centers the rotors, It looks like you might be planning on machining that as a separate piece? It appears your spacer ID is the the OD of the flange? Inquiring minds.
I have at least one front wheel set up that needs spacers also. Since I don't have your machining expertise I have thought of cheating and butchering apart a mag front wheel and machining a pair of spacers out of the hub, That way most of the hard work is already done.
Keep the thread and pictures coming please!

gggGary said:

Now I gotta ask, what about the "centering flange" for the rotors on the spacers? The stock location and the Omar's kit have a flange that centers the rotors, It looks like you might be planning on machining that as a separate piece? It appears your spacer ID is the the OD of the flange? Inquiring minds.

Click to expand...

Good eye, good question. My spacer ID is the OD of the "centering flange". Properly, the flange is what locates the disc rotors, while the 6 bolts just clamp it. In this application, the spacers ended up at an awkward thickness; thick enough that the flange on the hub itself doesn't protrude far enough out to locate the disc rotor, but thin enough that there just wasn't material enough to allow for the step-down in ID.

My plan to address this is to clamp and center the rotor and spacers together off the wheel, and drill them for a couple small (~1/8") roll pins. The pins don't need to be significantly strong, just precisely located. As with previous machining steps, I'll use the excellent Omar's piece as a guide to keep everything dialed-in. And yes, I'll take pictures...

The last moving parts of the rear suspension are done. Finicky welding of dissimilar materials, but the finished dogbone links look as good as could be hoped for.



The links are 3/16" x 1" plain mild steel, and the pins are 3/8" hard-chromed mild steel. The pins are pressed through machined bores in the plate, and welded on the outside only. I would have liked to make the whole thing out of hard stainless or chromoly, but getting just the few small pieces I needed meant buying waaay more material than I wanted to.



Cut to length, threaded for fine thin nuts, with oilite bronze bushings installed. They don't rotate through hardly any angle, but the whole weight of the bike is carried by them... There's room for larger and/or more elaborate pieces, if need be, but for now, I'll just be keeping a close eye on them.

Fought through my bronchitis today and knocked a couple items off the list... After fitting, cutting, and priming the dogbone links, I tackled the front wheel/brakes. With all the forum "encouragement", and without access to the bandsaw today, I did not cut up any old caliper bodies... Just measured and ground-down a spare to determine a safe "go/no-go" line, then copied it onto the rebuilt bodies:



I think there's still room to take another hair off, but I now have a half-spoke-diameter clearance, so I'll run it and watch for issues.

I also fine-tuned the wheel spacing. The left side was a little tight. I picked up a handful of 11/16" machine bushings, 18Ga to 14Ga thickness, and worked through the combinations until I had the spacing dialed.
In this shot, I was just a hair wide:



Clearances (spokes to caliper, disc to fork leg) generally good, but the disc rotor not quite centered in the caliper. I kept going all afternoon until it was right. Stupid stupid job (lift bike, pull calipers, pull axle, change shims, remount wheel, remount calipers, repeat, repeat, repeat) but it's done, and I'm happy.



Everyone's taste is different, but I'm totally diggin' the modern brakes with the 19" shouldered rim and spokes. (Sorry about the shaky picture).

Still need to pin the disc rotors to the spacers, and am waiting on fresh fasteners from McMaster-Carr. Need lines and pads too of course, but all the fiddly #%%^$ machining is done!

I'm glad for the kind words and support of the people following this thread...

gggGary said:

Since I don't have your machining expertise I have thought of cheating and butchering...

Click to expand...

I read this again, and I thought I should make a sort of "full disclosure". While I consider myself a fair mechanic and do my share of fussy fabrication professionally, I am not a machinist. So both by way of explanation, and to encourage anyone else in a similar situation, I say:

This is my first motorcycle, bought last Memorial Day. I have never before done any motorcycle modification or fabrication. Prior to about five weeks ago, I had never used a milling machine or lathe. My own shop has nothing but basic hand tools. I trade labor for a few hours/week of supervised access to machines, and pay for every scrap of welding.

Like most backyard builders, it's a constant struggle to fill the gap between my resources and my expectations. To do so, I research exhaustively, and mock-up extensively (I think I once made a mock-up of a mock-up). Everything I try my hand at is done with the full realization that it may not work, and a healthy expectation that it will probably have to be completely re-engineered at some point.

Whatever budget I might have had, I blew WAY through it months ago. But with this and a few other previous non-motorcycle projects, I learned long ago to avoid being "penny-wise and pound-foolish". It always costs more to do it the cheap way twice than to do it the expensive way once, so I try to go for the best materials, tools, and services I can afford (even when I really can't afford them). Even so, I definitely do my own share of "cheating and butchering"!

I read other build threads and am amazed at the work going on out there, and stoked to see all the glamour-shots of bikes nearing completion. In contrast, I scroll back through this thread and think, "Wow, what a bunch of boring pics of random bits of fabrication...". I'm not trying to show "machining expertise" (hah!); it's just that I've never done any of this before, and it's all new and interesting... and I've always wanted to see the steps that other builders seem to never show!

Anyways, I'm really grateful for the support and encouragement, but please, nobody should think that I'm any sort of expert, or believe for an instant that they couldn't do way better with less.

Borrowed a set of -4" rise wide-center clubmans to screw around with...



Maybe an inch lower than I'd like, and too wide overall... but I like how the wide center fits over the upper triple and curves down parallel to the upper fork tubes. Happy to see that the hydraulic reservoirs shouldn't stick up above the triples. Gonna have to play with this a bit...