Head Milling Question

[Steve]

That's what I was suspecting. There's just something inside me that wants to know how many tenths of a degree the timing might be been retarded.

.

[bwringer]

It's not necessary to remove all the pitting, just that around the critical sealing areas. The deepest pitting typically occurs in the vicinity of the stud holes because crud falls down. You don't need to remove all the pitting there and trying to do so won't add value to the process.

Yep. Glad to see someone else noticed this. On liquid cooled engines, you have all sorts of coolant passages to worry about, but on a GS head, all you need to worry about is the sealing around each cylinder, the four oil passages at the corners, and of course the tunnel in the middle. The pitting can get pretty deep in the other areas, but you don't really need to worry about it at all.

Also, with the newer Suzuki head gaskets you don't need the big square o-ring around the middle tunnel any more. Just leave it out and save yourself the $12.

I've degreed camshafts on a built-up KZ engine with aftermarket camshafts. The process is fiddly but fairly straightforward in theory.

You might have to dig to find a machine shop that will do a proper job of slotting the sprockets (we had a bit of trouble with this... not something you should just let Skippy the intern take a whack at with a Dremel). You've also just added another potential point of failure, so you have to make VERY sure the screws holding the sprockets in place a properly torqued with the proper thread locker, and re-check with every valve check.

We also learned, after an embarrassingly extended period of mathematical confusion, that there are two kinds of degree wheels, 180 degree and 360 degree. We had one kind, but the instructions with the camshafts assumed the other kind. Took us much longer to sort that out than it should have...

Overall, the difference a skim cut or two would make is very small. Plus, I'm not sure we have exact data on what the timing should be for some stock GS engines.

[Steve]

..., I'm not sure we have exact data on what the timing should be for some stock GS engines.

Could it be as simple as looking at the specs in the manual?

Yeah, it won't be as accurate as actually measuring what's there, but it should be close.

Just as an example, here is what I got using Web Cams calculator for my 850:



Cam Calculations - Lobe Center / Duration

---

Overlap: 64.00 degrees
Intake Duration: 276.00 degrees
Exhaust Duration: 272.00 degrees
Intake Installed Centerline of 100.00 degrees ATDC.
Exhaust Installed Centerline of 110.00 degrees BTDC.


The '79 850 had different timing, here are its numbers:
Cam Calculations - Lobe Center / Duration

---

Overlap: 54.00 degrees
Intake Duration: 276.00 degrees
Exhaust Duration: 272.00 degrees
Intake Installed Centerline of 110.00 degrees ATDC.
Exhaust Installed Centerline of 110.00 degrees BTDC.

I have not ridden a '79 850 to compare the powerband, but supposedly, the 10° advancing of the intake carb should make better low-end torque.

.

[bwringer]

Cool, I had absolutely no idea the OEM specs would be in the manuals!

[limeex2]

I was told to run 104 intake/106 exhaust on a street GS1000.