TOPIC:

Paul,

Before any machining is done, you can measure the valve stem protrusion in the shim bucket pocket and see if it's within specs (reference pages 178-179 in the service manual.. Re-cutting the seats (top dressing and bottom dressing) will narrow the seat width but if the stem protrusion is out of spec and to the high end of the spec 38.00 mm), the only way to bring it back in is to replace the valve seats. Yes, you can grind .3mm off of the valve stem but that only buys you 2 shim sizes.

I have bought new seats from Kibblewhite Precision Machining Inc. and will be replacing mine. The old seats are out (sucked them out with TIG.)Taken measurements and ordered the new seats. I've chosen to machine the new seats to fit the head rather than machine the head to fit the new seats. Been tied up with other things lately, but I'll be back at it shortly. I could have had KPMI machine up a set of custom seats and to be honest, I didn't check on the pricing for that (should have)

You can see where I'm at here. kz1300.com/index.php/forum/bike-projects...-1980-kz13?start=156

I'm a bit confused about the re-machining. Seats are machined using guides which go into the valve guides - that keeps the right angle. If they were machined with a wrong angle, then how? Just free handling them? Well, in that case, I guess there is another shot at that. Yet, if wrong angles were forced using guides, I'd kind of worry about the guides.

I guess one option is to get new seats and change them, then do all the cutting. In this case, you're valves now might be shaved 0.3 mm unnecessarily. I'd suggest pause, lay out all on paper and think everything over. I'd tell them to stop and press new seats. Maybe even valve guides. Then I'd get back to valves and adjustment.

Just in case, I still have that cylinder head. I could ask for having it done here. The Canadian 'peso' is cheap, perhaps that would not break your bank. Just machine the seats and then you'd do the valve adjustment there. You can always write me about it.

The seats are 'faced' to fit individual valves using cutters that use the guides as a pilot. What Kawboy is referring too is machining new seats to be installed in the heads. Once installed, the new seats will still have to have faces cut using the valve guide tools.

Kawboy wrote: I have bought new seats from Kibblewhite Precision Machining Inc. and will be replacing mine. The old seats are out (sucked them out with TIG.)Taken measurements and ordered the new seats. I've chosen to machine the new seats to fit the head rather than machine the head to fit the new seats.

What's the machining plan? Do you make up a custom mandrel to hold the seat? Are they difficult to machine?

What Kawboy is referring too is machining new seats to be installed in the heads.

I was referring to machining seats already installed, not machining the head for the seats.

Bucko wrote What's the machining plan? Do you make up a custom mandrel to hold the seat? Are they difficult to machine?

I bought 37 mm and 32 mm powder metal seats from Kibblewhite. The OD's are oversize by about .012" when accounting for a .005" interference fit. I have a tool post grinder on my lathe and I'll chuck up the seats as lightly as I can and grind the excess off. Then the seats can go in the head. The ID's are undersize and the height is too tall but that machining can be done by the seat cutter that I've lined up to do the work. The local machine shop has this machine and she's a beauty. When they cut the original seats for me, they all fell within .002" in depth. My only mistake was NOT taking that stem depth measurement before asking for the seats to be cut. Had I done my homework, I would have known to go straight to seat replacement.

This is a Sunnen SGM1500 with an air float deck for aligning. A really well thought out machine.