Moderate Project 1979, brake upgrade thoughts

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markmakeitso

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Hi all,
Been on the site for a couple years, but haven't posted a ton. A friend bought a $600 '79 to ease back into riding, and then upgraded to a newer cruiser. She sold the bike to a different friend of mine, who's brand new to motorcycles and skeptical about getting into an MSF course this summer. We'll see.
In the meantime I've been working on a few tasks to whip this thing into shape. We put a relay in it before, which uses the original coil power to trigger, and then passes battery positive directly to the ignition coils (and soon to the charging field coil also). New Emgo coils will maybe clear up a dying when hot problem she ran into last summer. New front tire, chain and sprockets, battery, and low rise handlebars and it's turning into a fun little town bomber. Snagged some cheap GM TTL coils to experiment with also (D514 and D585s I believe) after a friend had spectacular success using some 3.1L coils on his old Honda twin.
Exhaust is off for welding next week, so I took the pause to measure up the brake caliper mounting. Kind of thinking of doing the 320mm rotor and Yamaha blue dot caliper swap, but for giggles I mocked up a 6 pot Tokico caliper that was sitting around the garage. It's...tantalizingly close on the stock rotor actually. The inner caliper body hits a little bit on the cast spokes, but not before the caliper is slid on deep enough that the pads have full overlap on the rotor. A fairly thin spacer (1/8-3/16") laser or plasma cut to match the rotor mounting pattern would probably give enough room for the caliper while still allowing the rotor to center on the existing spindle diameter. Then an adapter bracket for 4 bolts would be pretty easy to draw up also.
Pics here if anyone wants to check it out:
https://www.flickr.com/photos/35465757@N05/albums/72157714124790748
 
Welcome! The bike is a 80 -SG It will help when buying certain parts.
 
Couple hours out by the garage today, pretty good progress. Bunch of rewiring done, as I found several problems before. Currently the 3 AC wires bypass the harness completely and go straight to my Rick's combined R/R. A relay provides power directly to the field coil and the regulator brown wires. The last bit to do is working on the 6 pin connector from the R/R (used to have 3 whites, plus red and black). Found varying voltage drop over the 2 sides of that connector, so think I'll replace the 6 pin with a 2 terminal connector, and maybe run straight to the battery instead of into the harness. At some point I should have just redone the entire harness, but I'm trying to get this thing back on the road faster than that.
Good enough to take for a quick spin before dark. Runs up to 50 pretty good, and that's as fast as I went in town. Next time perhaps I'll get some highway time. Before that I should probably check ignition timing and spend a little time on carb tuning. Starts up nicely on one choke click right now.
Couple little things to buy also: rear taillight cover, clutch lever that isn't so sloppy on the pivot, and maybe some brake improvements too. Good stuff, kind of excited again.
 
Jay said:
That Tokico looks like the 6 pots the older ZX7rs had. They are marvelous.
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Think these were off a fairly early GSXR, but have heard that Kawasaki dabbled with them also. Mixed reviews out there, and the New Hotness is obviously monoblock radial calipers. Rode the 400 for a few miles today, and was reminded how thoroughly mediocre the stock setup is. Measured up for a braided front hose, that'll do for now. Hopefully further upgrades later this year.
 
The 7R's definitely used those calipers (Tokico 6 pots, that look just the same. Not certain if your specific one came from a 7R), and as long as all 6 pistons operated, they were dynamite.The 7RR's at the time used Nissin 4 pots. The guys that raced the 7RR's would actually switch to the 6 pots for better feel.

FYI - the 6 pots are known for freezing up pistons. Just make sure they are all operating.

Monoblocks are great. If you go that route just avoid the monoblocks on the 636's. They are junk. I have rebuilt more than my fair share of them. I have swapped monoblocks onto a few bikes, and all of my track bikes have been monoblocks with radial masters.
 
Weellll, some updates on the off chance anyone cares. Awhile back I changed the oil and filter and filled up with non-oxy gas. Also installed the new braided brake hose, lever is very hard instead of spongy now. Brake feel isn't amazing but stopping is very improved. Two or 3 days later it starts running on only the left cylinder. Carb has fuel, both wires trigger the timing light fine, and it sparks against the head fine also. Fought with that for a bit until I finally tried swapping the new Emgo coils left and right. Yup, dead cylinder moved to the other side. Sigh, Had hoped for better than 100 miles out of new coils. Ordered up another one, but it also renewed interest in setting up GM intelligent coils as a replacement. Think I figured out a plan to trigger them using the stock ignition system timing without a lot of hassle or extra parts. Let you guys know if I make any progress on that project.
 
Got everything hooked up the other day and gave it a shot on one cylinder. Middling success honestly. The plan is to replace the coil primary winding with a fixed resistor that has switched battery voltage at one side, and goes to the ignition module on the low side. Measured at that low side there should be a square wave, which is low when the "coil" is on and charging, and high when current stops and the coil and plug fires. I have an inline 5V regulator, and then pass that 5V square wave to an inverter (eventually perhaps a hex inverter chip), for now an Arduino Uno that just inverted the logic from a digital input to a digital output. Kind of overkill, but the Uno also allowed me to perform a series of sparks from a laptop command for testing purposes. The 5V square wave charges the GM coil during high status and discharges at the negative edge.
Results? Mixed. There was no further function to the Uno besides inverting the logic of the input, and it really should have some software filtering and checking. On kickstart it didn't immediately fire on both cylinders, but when I revved it up on 1 cylinder it was sometimes starting to fire on both for a little bit. Wanted to get my PC scope on it to check signals but it acted up on me out in the driveway. Such is life. So kind of promising. No reason this couldn't be doubled up for both cylinders soon, or even the XS triples and 4 bangers. It's also possible to add this modification without hacking up the stock harness at all. Fun stuff.

Pic attached, here's some info on the GM LSx coils:
http://www.megamanual.com/seq/coils.htm
...and a long old video:
 

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amc49 said:
And the purpose of all that is............?
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Of the long video, my longish post, or the project in general? Will agree, both the video and my post could be trimmed a fair bit. Got ideas for several improvements to the XS, depending on how long it stays in my garage perhaps. If you're not interested in the coil improvements you probably won't change your mind for programmable ignition curves, digital charging control, or CAN bus capability either.
 
Where is the value there?, the engine is so small there won't be a commensurate increase to the amount of work. Go simple to an easy understandable electronic and then leave it alone. You've gotten 90% of the value gettable there.

Of course your stuff and yours to do with as you will, I just believe things should have an outcome that accomplishes a useful something. Am enjoying reading about it, like the guy doing EFI on these. You're making my older brain work. SOMEBODY has to experiment to come up with the mods that push the power levels up and up, who ever dreamed 30 years ago of over 100 hp. 600s and even more now?

I say that as a person who used to overcomplicate almost everything whoppingly myself, when racing cars at a younger age I had the 'trickitis' pretty bad. It can be very helpful or your worst nightmare.

I created an electronic ignition for American Motors cars back in the mid '70s when we couldn't get one other than the crap low volt OEM first issue Prestolite breakerless. I also used 2 GM HEI modules to make an electronic improvement on 1st gen Honda DOHC 4's too, it used coils from '88 Chevy Baretta. In the late '80s.

That latter bike was definitely a case for programmable ignition curve, it has some head design flaws that make it have some value.
 
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A perfect example of too much complexity with no reward comes to mind right now, the Nissan VC-T turbo PLUS variable compression engine that was supposed to take over the world, I looked at the tech on them and too much doing too little, the engine is proving out now to not accomplish what they said it would. Why they added variable compression when you can simply alter same with the turbo and better computer control we will never know. For gimmick value only to wow the buyers. The variable compression adds double the number of engine parts and on top of that offers real opportunities to wear out the engine much faster, but you don't hear a word of that with all the accolades lauded to it.

The current state of things in Nissan CVT and the recent Ford DCT fiasco that largely pushed them to drop sedan cars are two other outstanding situations showing what can happen when you get the engineers too wrapped up in the tech to lose sight of true objectives.
 
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