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Cool thank you! Out of curiousity how did you come up with the add 3T to stock though?
And you said 16T for the front sprocket but then listed a 15T in the second part of your reply. I thought I saw a 39T rear but I may not be looking at the right thing. I'd just call Z1E but their phone number doesn't seem to be listed anymore - sent and email but that may take a while to get back... 

wrote:

Cool thank you! Out of curiousity how did you come up with the add 3T to stock though?
And you said 16T for the front sprocket but then listed a 15T in the second part of your reply. I thought I saw a 39T rear but I may not be looking at the right thing. I'd just call Z1E but their phone number doesn't seem to be listed anymore - sent and email but that may take a while to get back... 

My bad on the 15 vs. 16. 16T is correct.  You can check yourself using one of the many sprocket calculators around on the internet.  Compare the "pitch diameter" of a 13T 630 sprocket to a 16T 530 sprocket.  They will be very close in size.

Alright crew here's another one - did an oil change on this bike and put in 3qt of 10w40 full synthetic as a starting point so we'd be nice and happy between the low and high fill marks. I've ridden the bike about 40 miles since and the other day went to hop on but checked the oil before taking off the center stand. We were at the bottom of the eyeglass....I'm stumped. Not leaking anywhere under the bike, plugs aren't fouled, although there is a decent amount of carbon on the piston heads (24.8k miles on the clock). I'm wondering if it's valve seals? When I had plugs out I hand spun the engine and there was definitely oil on the seat of the valves that I could see. Thoughts? 
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Also because it isn't in the manual the I found, and a few people seem to have the same question here is the loading info for the 1981 KZ750 H2 LTD straight off the stem:
GVWR 860 LBS
GAWR FRONT 375 LBS with stock wheel/tire at 25psi
GAWR Rear 562 LBS with stock wheel/tire at 25psi

hope someone else finds this useful! Thanks! 

Only 3 quarts?  No wonder it is low on oil.  Why didn't you put in the correct amount of oil to start with?    Ed

Because I'm a cheap bastard and rather than put in 3.5 I put in 3, since that brought it to about the middle of the sight glass, and there's a small chance it's going to all get drained again soon anyways. 

When changing the oil it is not unusual for the oil in the site glass to be a bit high until the bike's engine has run and been allowed to cool down.  I suggest you put in the correct amount of the correct type oil and then see if the oil level goes down after a ride.  Be sure the oil is JASO-MA compliant.  That should be shown on the oil container's label.  Using the wrong oil can ruin the clutch.  Ed

Went to change the fork oil and seals because who knows when it was done last... Photos of the old seals and retainers attached. Yikes. 

In my disassembly, there was a part that seemed to be missing but the parts diagram is somewhat unclear. In the service manual it is called the piston ring, and resembles a washer, but in the OEM parts diagram it is part of the piston/cylinder unit. Neither fork had such a ring but each did in fact have a small black ring that fit into the groove at the top of the piston/cylinder.... Are they the same thing?