drilling exhaust flange holes to 8mm

Hello from Oz Gentlemen,

I have just fitted a different head to a Kz900 and found my exhaust flanges need to go up in stud hole size, has anyone experienced any problems drilling orignal KZ900 6mm flange holes up to 8mm to accept the Kz1000 sized exhaust studs? Bigger nuts of course but is there any other traps to be aware of?

As usual thankyou for your advice and MERRY CHRISTMAS! Hope you all have a safe and prosperous New Year riding.

Regards,
Kt

I'd get an 8mm reamer, use plenty of cutting oil/fluid to keep the cutting tool cool,use slow speed and plenty of pressure for a smooth hole.

For an accurate sized hole, try to use a drill bushing that can be clamped in place. To remove any Burr, a countersink at low speed will cut it away.

A good way to ream out the exhaust clamps/flanges would be to do them in a drill press. Clamp them down so they can't move. Possibly a 8.5 or 9mm reamer might work beter than an 8mm reamer due to manufacturing tolerances. So a little "Slop" will be needed.

thanks for the speedy reply, i have a nice new 8mm drill bit,but no reamers, looks like drill will have to do, hate to modify original parts,might see if i can hold off and buy some alloy units from Z1E after the holidays.
Kt

Ktm181 wrote:

thanks for the speedy reply, i have a nice new 8mm drill bit,but no reamers, looks like drill will have to do, hate to modify original parts,might see if i can hold off and buy some alloy units from Z1E after the holidays.
Kt

Hello Kt:

I have done exactly what MFolks suggested (had a head with slightly bent exhaust studs and had to enlarge some flange holes). Go slow, lots of cutting oil, and it works well with no problems.

There are several versions of the 6mm exhaust flanges. The very early ones don't have much meat around the stud holes. I would not drill those. If you have the later 900 flanges then yes, you can drill those. Use a 8.5mm drill bit. 8mm will be too snug on the studs.

The genuine Kawasaki kz1000 flanges are step drilled. The front (visible) portion is 8.5mm, the rear is 10mm. This makes it easier to get over the studs on the later KZ1000 (which had beefier frame tubes).

Why not just trade them for a set of 8mm Ones. I might even have a set of those in my extra parts.

thanks for the replies Gentlemen, excellent help and information as usual, i may have the earlier flanges so might have to do some shopping with Z1E after Christmas.

Regards,
Kt

thanks for the offer, but need to keep the originals for another head.

Kt