From the piston side.

I learned a lot about surfacing a cylinder head the last couple weeks.

Initially I tried a plate of glass with sandpaper spray glued to the glass.  There was a low spot, and the more I sanded the worse it got.  It turns out that the head has twice as much metal on the cam chain side as the other side - so sanding makes the head crooked and the more you sand the worse it gets.

So I tried my little milling machine.  I found out it is really not up to the job, and my narrow cutter left poor finish.  I found out that as I cranked on the wheels to move the table.....the up/down force I put on the handwheel was enough to deflect the table a bit.

I tried sanding just a little bit with my glass sheet and sandpaper.....it just kept getting worse as it sanded the edges but not the middle!  This proves that either my glass isn't flat, or the sanding process doesn't sand flat - or both!

Then I mounted a head and gave it a try......it worked great!

No more glass and sandpaper for me!

We used spray bottles of a product called Alum-a-Cut and used it liberally while cutting either on a mill or a lathe.  The stuff really helps out with the finish while cutting aluminum.

If you zoom in on the head you can see a spot on the top left that did not clean up with the first 0.001 cut - it did clean up on the second cut that was less than 0.001 more.

That is the head stud that functions as the drain for the oil from the head (left front).....I didn't want that leaking!

Yup...  drooling!

DragBikeMike wrote on 02/04/22 at 02:07:51:


I was able to get some measurements to day that I think are consistent enough to believe.  I did not measure this head before I started sanding/milling/cutting - I never expected it would end up being this complicated.

I first tried measuring the distance from the cam bearing surface to the head.  I checked 3 other heads and they measured 2.730", 2.732" & 2.735".  The cut head measured 2.715" - that would indicate that I cut off 0.015" - 0.020".

The second measurement I tried to use was the distance from the head surface to the space between the intake and exhaust valve on the side opposite the head.  The 3 stock heads all measured at 0.745" - while the cut head measured 0.7200.  This would indicate that the head was cut 0.025".

It is a little frustrating that those measurements differ by 0.005" - 0.010" - so I am tempted to believe the measurement to the combustion chamber and say that 0.025" has been removed.  That is likely the measurement that is more meaningful as it is from the piston side of the head.

Good call Mike.....the flange of the stud does protrude a few thousands.  I will likely drop the hole depth in the head a bit.      

I have been working on the bike a bit - but some of it was not too exciting or worthy of photos.

It took me quite a few hours to get the nuts/bolts/spacers ready for plating.  First they got a soaking in phosphoric acid to remove any rust and the previous plating - then they were rinsed and dried.  I took them up to the plater and showed them to him....he suggested more work to get them prepared a bit better for more reliable plating.  So I spend many hours last weekend - some parts got bead blasted, some got attention from the wire brush, some got bead blasted and wire brushed....and the pieces that were too small got another acid bath, rinse and drying in the oven.  They are now at the plater getting barrel plated with Zinc Chromate.

I also got some springs at the hardware store that will allow me to assemble the top end and check clearances between the piston/valve so I can select a head gasket thickness to use with the 97mm piston.  The springs will allow me to check clearances with only light pressure on the cam and rockers.  The closest springs I could find were twice as long as the stock springs - so I bought 2 and cut them in half to make the 4 springs I need.