Seeing as there's nothing happening on this site thought I'd share what I've been doing to the H2.

Looks like you did your table too...

Did you chamfer those holes?

My disc pictures are up on a Kawasaki Triples website in the States and this guy just posted up on the thread there. I feel totally honoured. Tuner Dave worked on the first Kawa triples racers over there back in the '70s. Awesome story and a little bit of history about drilled discs!

H2rTunerdave

Nice work, good design.

Being the FIRST person to ever cross drill a Kawasaki brake disk, and also, I am sure, any motorcycle brake disk, NOT DEBATABLE, FULL FACT, AND I DO NOT CARE WHOM THINKS DIFFERENTLY, THEY ARE DEAD WRONG, I WAS THERE, DID IT, THEY WEREN'T, DIDN'T (Team Kawasaki Road Race, December, 1972, 72 one half inch holes), I have heard every reason for doing so in the known universe, EVERY brilliant, to totally moronic reason..

The original design of 3 rows of 1/2 inch holes, came from Dave Hussey. He was a Bertea Corporation design blueprint engineer by day, did all the blueprints for Morris Mag Wheels in the evenings, right next door to the race shop. Dave took a 1965 Porsche Can-Am car drilled disk and revised it to work with our disks.

He walked into the race shop one evening when Steve and I were working very late, picked up a disk, said "These things are way heavy". We asked if he had a cure. An hour later, he brought the disk, and a drilling pattern back for the holes, and I drilled them late at night, 4 sets for Yvon's bikes, so nobody but Steve, Dave and I would know what we were up to.

We used straight off stock street bike H2 disks on H2R's back then for the front, MG 8 inch cast iron disks for the rears..

The main reason was just what Hussey said, too heavy, had adverse effects on both braking, and un-sprung weight for the front suspension to handle.

We kept it secret, even to other team members, until Daytona, 1973. We sprung it on the world then, worked a lot better than undrillled disks. The rest is history.

Below is an archive photo of Yvonne Duhamel on a 1972 H2R

WillH.

I went round the houses on that one.

I know that putting a chamfer on every hole, front and back, would seem the right thing to do but here was my issue.

Because I haven't got a CNC set up and everything was done by hand it's very, very hard to use a larger diameter drill and cut the chamfer so that every hole looks identical. Just a fraction of a mm more cut results in a much bigger chamfer and you can end up with everything looking a right mess. I did a lot of tests and even when the work is clamped tight down onto the bed and the press stop adjusted the difference between two holes can be visually unsatisfying for me.

So I decided to just try it like this first and see what happens. Obviously there was a small amount of burring on the rear of the disc when the drill cut through. As well as this the surface actually bulges very slightly around the hole so you get a minute ring of raised metal around the edge of each hole. So after the holes were all finished I very patiently filed across the surface of every hole and then used emery stuck on a sheet of glass to fine finish the surfaces so they were completely flat.

So, no, there's no chamfer but the surfaces are probably twice as flat/smooth as they were before because they were used discs and had quite a bit of radial lines from many years of use.

My logic says that the pads will be OK working on this surface. I've had quite a lot of modern drilled and slotted discs and they either appeared to have no (or very little) chamfering when new and once they started to wear down then this disappeared anyway. I think there would be a problem if I'd left any raised surfaces or the disc wasn't flat.

We'll see. So far I've only done a few dozen miles just to check everything out and all seems fine. The pads obviously need bedding into the new discs but so far you can see that the surface of the disc is getting worn into a shinier finish (the emery finish was a matt surface) and everything is even and looks OK.

A 90* chamfer bit and use the stop on your drill press for height control if you have one would be the way to do it and keep it uniform.

Keep an eye out for cracks without the chamfer. Porsche drilled disks sometimes crack when worn below the chamfer.

How much weight difference before after? Many moons ago I did the front and rear of my Commando and had large radial reliefs machined between the mounting bolts for added weight reduction. Made a bit of difference on those thick iron disks.

I wasn't really doing this for weight saving but the original un-drilled disc weighs 3,040g. This pattern with 150 holes with a diameter of 6.5mm. The overall weight is 2,769g which is a 273g saving in unsprung weight per side which is quite considerable.

You get rid of a lot of material - and yes, it all ends up in the carpet!

How's the H2 been going Bic?

re countersinking - Willh is spot on with his comments.
Just buy a countersinking bit to suit the hole diameter and set the depth stop on the drill press. This will give you the uniform countersink depth you require. You don't need to be precise when lining up the hole centre with the centreline of the countersink bit because once you start and the two meet it becomes self aligning and the depth stop does the rest. Just remember to allow the disk to float so it can self align to the centreline of the countersink bit, clamping the disc is not the right way to go in this process and is not needed because of very small cutting forces.
It is a good idea to put a small countersink on both sides of the holes to relieve any stress points on the holes edges.
bike looks good.