Pulled head and found 1 oily combustion chamber

There's nothing wrong with helicoils. They're stronger the the originals threads. I would run a tap thru all the threads to clean them up. Maybe torque town the caps and make sure they all hold torque.

For the head you should take it apart, media blast, match the intake runners to the carbs holders. I would then instal ape valve springs and Viton valves seals.
Depending on the mileage you should consider new valve guides.
I would remove the jugs without dropping the Pistons from their bore and replace the base gasket along with the oil passage orings

Spark plug is darker on side of intake valve. Guess which valve seal is bad?
Scratch that! Spark plug is NOT oily.
Oil rings are probably stuck. People never flush engines.

Ok, I made a spring compressor and got the valves out today. All of the seals were brittle and probably on their way out and the seal on the exhaust valve in the problem cylinder was definitely leaking. The guides seem tight at least. Here are some pictures

So this motor has the goodies listed in your profile? Sounds like it must be a strong runner..... after cleaning up the head and valves betting it will be even a wilder ride...... I replaced all my cam cap threads with heli coils before I sent the head out so I wouldn't have to worry about them later so like stated your probably better off with em in.

Clean up the head and use some fine lapping compound to see how the valve and seats are. If there are blank spots or the seats are too wide, you need the have them ground. That being the case, the guides should be replaced as well.
Steve

There's a member on here, DFIGPZ, that sells sets of Viton valve seals for 22.00 delivered
Pete

Thanks guys. Yes Kzb2 650 the bike was pretty crazy before I started this project. I'm actually in the process of detuning it a bit which is why I had the head off. The cams I was running were a blast but not great for city riding and the bike was prone to overheating if I got caught at more than a couple red lights. I have a gpz intake cam and kz750 exhaust I'm putting in in place. No more rocket ship but should still be fun. I got myself the Viton valve seals. Is there any trick to removing the jugs without dropping the Pistons from their bore. I have a new base gasket I'd like to install along with the head but would rather avoid having to hone and get new rings.

Raise the jugs till you see the pins remove the two then do the other two

swest wrote: Clean up the head and use some fine lapping compound to see how the valve and seats are. If there are blank spots or the seats are too wide, you need the have them ground. That being the case, the guides should be replaced as well.
Steve

The guides or seals?

A three point seat grind should be done with new guides and seals.
Steve

swest wrote: A three point seat grind should be done with new guides and seals.
Steve

Yes, I misunderstood. So with new valve guides, a regrind is pretty much a given.

Yup. That's what I did in 87. I could have just slapped the thing together and rode it but while I had it down, was running a shop and had access to one of our best racing machine shops, I had them do a three point valve grind. I put in the guides before they got the head. (cheap bastard) I had them bore and match my pistons to the block I had from the Z2. I wanted it to last and I'm glad I did. I parked it after 5000 miles. Last year it got new valves, springs and Viton seals.
Who knew I'd be riding it at 62 like a 20 year old. :woohoo:
Steve