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1974jh5
Curmudgeon.
There was a tremendous battlethread on corner-carvers.com about drilled rotors. I lurked and just watched, at times I thought WWIII was going to break out, good thing no one had nuclear weapons. That site has disappeared, unfortunately. Even though it was full of sanctimonious flame war prone jerks they were definitely smart and there was a LOT of good tech info.
Anyway, the prevailing automotive wisdom is: on solid rotors for street or other low stress use, go ahead and drill away but don't expect great increases in brake performance. Same goes for slotting. Definitely chamfer the holes. For race use, do not slot or drill and be prepared to replace rotors often.
For vented rotors, there are a few out there (Brembo is one, IIRC) which have the holes cast in and those are not prone to cracking. Drilling a stock rotor quite often will put holes in the middle of a vane which leads to ugliness due to internal stresses. Again, OK for low stress use but not on race stuff.
The #1 brake improvement for racing is adding ducting to cool them. That one I have experienced first hand, when the brakes are shrouded by a wheel it's difficult to get air to them and that's why you see the big scoops etc. Some cars even run liquid cooled calipers with their own radiator! With XS rotors hanging out there for the world to see, that's not a problem.
Anyway, the prevailing automotive wisdom is: on solid rotors for street or other low stress use, go ahead and drill away but don't expect great increases in brake performance. Same goes for slotting. Definitely chamfer the holes. For race use, do not slot or drill and be prepared to replace rotors often.
For vented rotors, there are a few out there (Brembo is one, IIRC) which have the holes cast in and those are not prone to cracking. Drilling a stock rotor quite often will put holes in the middle of a vane which leads to ugliness due to internal stresses. Again, OK for low stress use but not on race stuff.
The #1 brake improvement for racing is adding ducting to cool them. That one I have experienced first hand, when the brakes are shrouded by a wheel it's difficult to get air to them and that's why you see the big scoops etc. Some cars even run liquid cooled calipers with their own radiator! With XS rotors hanging out there for the world to see, that's not a problem.
osteoderm
out of the box
"Battlethread" Haha! Well, just to dispel any pent-up opinions in these here parts, lemme say this right now: I have zero illusions about performance gains with any of my proposed drilling patterns. It's totally about the looks and losing a little weight. Neither am I ignorant of the issues; I don't want to compromise my safety just for looks!
I am completely sure that anything/everything I do to rebuild/redesign my front end will end up being more work, possibly more money, and gain me less advantage than simply swapping in a more modern front end. It's just the thin end of the wedge, and I'd soon have myself convinced that I just need a whole new modern bike.... That's just not the point.
Same goes for the monoshock rear. Is all the hassle and expense worth it to modify a 37-yr old frame for 3 measly inches of travel? Of course it isn't, not if you look at it from a strict performance point-of-view. It has to be the most effort for the least gain.
I was talking to a client today about this. His car has a 450HP Brodix aluminium small-block under the hood, with cast-iron solid axles, drum brakes, and 4 skinny skinny tires. Why What's the point? 'Cause it looks cool as hell, is fun as anything to drive, and makes you giggle like a 6-yr old each and every time you get in and fire it up... and you'll never get passed by yourself on the road!
I sure appreciate everyone's input and commentary here on this forum. I want my complete bike to be at least just as safe and reasonable to ride as it was in stock form, hopefully just a little better. I want something that tickles my fancy every time I pull the cover off and fire it up, the last time the same as the first. I'm certainly not going to get hung-up on wringing every last bit of "performance" from my old bike...
I am completely sure that anything/everything I do to rebuild/redesign my front end will end up being more work, possibly more money, and gain me less advantage than simply swapping in a more modern front end. It's just the thin end of the wedge, and I'd soon have myself convinced that I just need a whole new modern bike.... That's just not the point.
Same goes for the monoshock rear. Is all the hassle and expense worth it to modify a 37-yr old frame for 3 measly inches of travel? Of course it isn't, not if you look at it from a strict performance point-of-view. It has to be the most effort for the least gain.
I was talking to a client today about this. His car has a 450HP Brodix aluminium small-block under the hood, with cast-iron solid axles, drum brakes, and 4 skinny skinny tires. Why What's the point? 'Cause it looks cool as hell, is fun as anything to drive, and makes you giggle like a 6-yr old each and every time you get in and fire it up... and you'll never get passed by yourself on the road!
I sure appreciate everyone's input and commentary here on this forum. I want my complete bike to be at least just as safe and reasonable to ride as it was in stock form, hopefully just a little better. I want something that tickles my fancy every time I pull the cover off and fire it up, the last time the same as the first. I'm certainly not going to get hung-up on wringing every last bit of "performance" from my old bike...
yamaman
xs650 addict
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Cool, if you cant have fun on your own $, you'll die waiting for someone else to put it up for ya! Iwould be wary of drillin to close to the edge of the disc, that is the most fragile part, and if it cracks, thats where it will be. good luck 
Posted via Mobile
Posted via Mobile
osteoderm
out of the box
I completely agree. Still doodling in CAD, and the holes are starting to get a little smaller, and a little further from the edge.
pregrid
XS650 Guru
And THAT, ladies and gentlemen, is why we do what we do. and those of us who don't realize it now hopefully will in the not too distant future. The man tells it like it is, this old lump is for fun, pure and simple. Anyone who has delusions to the opposite is, well, delusional. YMMV
Brother
XS650 Addict
Wait, what? You mean the XS650 isnt the fastest, most comfortable, vibe-free, and best handling bike ever made?
Now they tell me.
Nice build man, looking forward to your progress.
Now they tell me. Nice build man, looking forward to your progress.
osteoderm
out of the box
Phenomenal progress on the swingarm today! Finally got some time in with the Bridgeport; looks like the swingarm portion of the monoshock conversion will be complete this weekend.
Started out with the welded swingarm mounted to a base fixture.
Painted with layout fluid and some guides scribed in. Centered on the tube, 4-3/4" behind the center of the main pivot.
After the base fixture was solidly bolted to the table, we turned a bronze rod down to a tight slip fit, ~16mm, and chucked it in the Bridgeport.
Using the threaded adjustment built into the fixture, along with this quickie tacked-on turnbuckle, we tweak the swingarm until the bronze rod is a perfect vertical fit into the swingarm pivot sleeve. The idea is to make all further drilling/boring/reaming operations perfectly parallel to the main pivot.
An additional brace is welded in, then the whole thing is re-checked for plumb.
After confirming my center marks with the wiggler, the first cut is with a 4-flute 1/4" end mill. Unlike a drill bit, this has almost no chance of wandering off center.
Second cut was with a thin-kerf minimal-set 7/8" holesaw running at 160rpm...
...followed by a 1" ream running at 120rpm.
With three layers of steel, curved in two directions and sloping away from the perpendicular, there's plenty of room for error, but the solid jig and careful setup turn out to be worth the effort!
The second bore is trickier; the end mill won't reach through to start the the hole. Instead, we transfer-punched a center and drilled a 1/4" pilot with a long bit and a steadying bushing clamped to the table. (Knew I forgot to get a picture of something!). Here, we're set to run the 7/8" holesaw through. The pilot bit in the holesaw mandrel has been replaced with a smooth 1/4" rod, so it can't catch in the pilot hole.
It took the full travel of the quill, plus a little travel of the knee, to get the 1" ream all the way through. But after a couple clean passes, the dogbone pivot shaft is a perfect fit.
I have my fingers crossed that the welding will be finished on Saturday!
Started out with the welded swingarm mounted to a base fixture.
Painted with layout fluid and some guides scribed in. Centered on the tube, 4-3/4" behind the center of the main pivot.
After the base fixture was solidly bolted to the table, we turned a bronze rod down to a tight slip fit, ~16mm, and chucked it in the Bridgeport.
Using the threaded adjustment built into the fixture, along with this quickie tacked-on turnbuckle, we tweak the swingarm until the bronze rod is a perfect vertical fit into the swingarm pivot sleeve. The idea is to make all further drilling/boring/reaming operations perfectly parallel to the main pivot.
An additional brace is welded in, then the whole thing is re-checked for plumb.
After confirming my center marks with the wiggler, the first cut is with a 4-flute 1/4" end mill. Unlike a drill bit, this has almost no chance of wandering off center.
Second cut was with a thin-kerf minimal-set 7/8" holesaw running at 160rpm...
...followed by a 1" ream running at 120rpm.
With three layers of steel, curved in two directions and sloping away from the perpendicular, there's plenty of room for error, but the solid jig and careful setup turn out to be worth the effort!
The second bore is trickier; the end mill won't reach through to start the the hole. Instead, we transfer-punched a center and drilled a 1/4" pilot with a long bit and a steadying bushing clamped to the table. (Knew I forgot to get a picture of something!). Here, we're set to run the 7/8" holesaw through. The pilot bit in the holesaw mandrel has been replaced with a smooth 1/4" rod, so it can't catch in the pilot hole.
It took the full travel of the quill, plus a little travel of the knee, to get the 1" ream all the way through. But after a couple clean passes, the dogbone pivot shaft is a perfect fit.
I have my fingers crossed that the welding will be finished on Saturday!
pregrid
XS650 Guru
wow, involved, but obviously worth the effort.
osteoderm
out of the box
Glad you think so... I'm not quite convinced it's "worth the effort", but I'm having fun!
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Having fun is the important thing.
Having tried several things, some improved things, some didn't, learned a lot about the bike in the process, so all was good.
Leo
Having tried several things, some improved things, some didn't, learned a lot about the bike in the process, so all was good.
Leo
osteoderm
out of the box
More welding today... Got lucky, and had my parts end up as part of a teaching session down at the shop; the resident super-pro showing the new guys how it's done.
Dogbone pivot shaft getting tacked-in...
...then onto the frame tabs for the rocker link.
Walter was happy with my metal-fitting, and I'm super-stoked with his welding!
The rocker link is deadly centered and parallel to the swingarm pivot.
Double-checked parallels to swingarm... just a little tweaking, now all good!
Two great welders, one fine piece of work.
Still plenty of work to go, but now I can get to roller; fit the wheels, set the ride height, work out the best upper shock mount and dogbone lengths, and get cracking on the seat mounts.
Dogbone pivot shaft getting tacked-in...
...then onto the frame tabs for the rocker link.
Walter was happy with my metal-fitting, and I'm super-stoked with his welding!
The rocker link is deadly centered and parallel to the swingarm pivot.
Double-checked parallels to swingarm... just a little tweaking, now all good!
Two great welders, one fine piece of work.
Still plenty of work to go, but now I can get to roller; fit the wheels, set the ride height, work out the best upper shock mount and dogbone lengths, and get cracking on the seat mounts.
Very nice! You've spent more time and energy on your swingarm than most people do on their entire chassis. Keep the pictures comin'! I love seeing machining photos and the detailed explanation of the process and tools used. 
osteoderm
out of the box
Tell me about it...
My "day job" is all detailed fabrication, and my own habits are towards the same. As much as I'd like to just "get'r done", I can't fight my nature, and these things just keep going and going... I'm pretty sure by now that it may actually be faster, easier, and possibly even cheaper in the long run to just fab a custom frame from the beginning! All this modifying and re-engineering of the stock parts seems endless.Keep the pictures comin'! I love seeing machining photos and the detailed explanation of the process and tools used.
My pleasure! I'm trying to post the sort of thread I like to read.
It always drives me crazy when I read about some awesome mod somebody did, but can never see exactly how it works or how they accomplished it.
hooktool
XS650 Junkie
Well, you have a lot of people following, I expect. Keep up the good work.
John
John
osteoderm
out of the box
I picked up an All Balls needle-bearing kit for the swingarm awhile back, and finally installed it now that the major swingarm machining has been completed. The stock plastic bushings in the TX750 swingarm looked okay, but it seemed silly to keep them after all the other work. Went with the All Balls kit off of eBay because Mike's kit was out of stock (a sadly familiar tale). Mike's advertises "needle thrust bearings", which I'd like to confirm (the pics on the website are inconclusive). The All Balls kits uses very simple plain thrust bearings instead.
The four needle bearings bearings in the kit seemed fairly standard, and pressed in okay. For all my pressing operations, I used a length of 5/8" threaded rod with washers and coupling nuts to slowly ease the parts home. I checked the fit of the supplied bearing sleeve, it it seemed okay. Pressed the plain flanged thrust bearings in next. Something didn't seem to be right; the new sleeve seemed too tight...
Here, the original TX650 bearing sleeve is shown on top, with the replacement All Balls sleeve on the bottom. The TX650, TX750, and new sleeves all have the same overall dimensions, but the stock Yamaha parts are reduced in the central section, and have those grease ports.
In the end, I touched up the TX750 sleeve (it was in much better shape than the TX650 sleeve shown in the pic) with a little scotchbright, lubed it up, and pressed it in, praying the whole time that it wasn't too tight and wouldn't jam. As tight as the was pressing in axially, it feels excellent in rotation, if a little stiff (no "bumpy" feeling from the bearings).
With everything tightened up and plenty of grease pumped in, the swingarm bearing action is butter-smooth, despite my concerns with the initially tight fit. The supplied oil seals are pretty lousy though... The thrust bearings kinda pop into them, but there isn't any real sealing pressure. It's like it's missing that tiny spring o-ring to squeeze the lip into place.
The four needle bearings bearings in the kit seemed fairly standard, and pressed in okay. For all my pressing operations, I used a length of 5/8" threaded rod with washers and coupling nuts to slowly ease the parts home. I checked the fit of the supplied bearing sleeve, it it seemed okay. Pressed the plain flanged thrust bearings in next. Something didn't seem to be right; the new sleeve seemed too tight...
Here, the original TX650 bearing sleeve is shown on top, with the replacement All Balls sleeve on the bottom. The TX650, TX750, and new sleeves all have the same overall dimensions, but the stock Yamaha parts are reduced in the central section, and have those grease ports.
In the end, I touched up the TX750 sleeve (it was in much better shape than the TX650 sleeve shown in the pic) with a little scotchbright, lubed it up, and pressed it in, praying the whole time that it wasn't too tight and wouldn't jam. As tight as the was pressing in axially, it feels excellent in rotation, if a little stiff (no "bumpy" feeling from the bearings).
With everything tightened up and plenty of grease pumped in, the swingarm bearing action is butter-smooth, despite my concerns with the initially tight fit. The supplied oil seals are pretty lousy though... The thrust bearings kinda pop into them, but there isn't any real sealing pressure. It's like it's missing that tiny spring o-ring to squeeze the lip into place.
osteoderm
out of the box
I hadn't yet convinced myself to go for the rear disc conversion, but a decent deal on another 19" D.I.D. wheel came up on eBay, so...
I know these high-flange rims aren't to everyone's taste, but I like 'em. Light, strong, and annoying to clean. I was originally keeping my eyes open for another bare front hub, thinking of converting the stock 18" rear wheel to disc, but now the 19" front and rear combo is sticking in my head.
A 18" rear / 19" front combo sure is easier for aesthetic tire choices... I like the look of the 90/90-19 for a front tire, but what to pair it with in the rear? Seems like I'm stuck with 100/90-19 front and rear... Or... what's the prevailing wisdom re: running a 90/90-19 on the back?
I keep imagining that there's something like a a 120/70-19 tire available for the back. Yeah, right.
I know these high-flange rims aren't to everyone's taste, but I like 'em. Light, strong, and annoying to clean
. I was originally keeping my eyes open for another bare front hub, thinking of converting the stock 18" rear wheel to disc, but now the 19" front and rear combo is sticking in my head.A 18" rear / 19" front combo sure is easier for aesthetic tire choices... I like the look of the 90/90-19 for a front tire, but what to pair it with in the rear? Seems like I'm stuck with 100/90-19 front and rear... Or... what's the prevailing wisdom re: running a 90/90-19 on the back?
I keep imagining that there's something like a a 120/70-19 tire available for the back.
Yeah, right.
pregrid
XS650 Guru
If I had gone with spokes on my build THOSE are the wheels I would have used. To me, they're the best looking ones out there. Good choice!
Most 90/90-19 tires are front tires, not built to withstand rear wheel stresses.
A 100/90-18 on thr rear will run well with a 100/90-19 on front.
Leo
A 100/90-18 on thr rear will run well with a 100/90-19 on front.
Leo
1974jh5
Curmudgeon.
I went with an 18" rear mostly because of the larger selection of easily found street rubber.
