manual says136 to 209psi, 1981 kz650 compression

Can't be right, but see the kz650 factory manual page photo below,
it says the nominal psi is 12.7 kg/cm^2 which when converted
(see www.onlineconversion.com/pressure.htm ) to PSI, is 180psi.

Also see wiki.answers.com/Q/How_do_you_convert_Kg_cm2_to_psi which
shows that 1 kg/cm^2 equals 14.2psi, so as confirmation, the Kaw factory shop manual for my
1981 kz650-CSR is nominally (12.7 x 14.2) = 180.34psi



So my factory shop manual says that the 'usable range' for cylinder compression is
from 9.6 kg/cm^2 to 14.7 kg/cm^2, which when converted to PSI means when I do a compression test,
anything between

136psi to 209psi !!!

What the hale! Sounds high!

I know, due to the fact that I checked the conversion in 2 different web sites (above) for
kg/cm^2 to psi, I know my math is correct.

Anyone concur that this factory shop manual is wrong?

I've never heard of stock psi being 180 'nominal' with 209psi being acceptable.

My 3 different Kawasaki Shop/Service Manuals for the KZ650 (1 printed 1976, 1 in 1979, 1 in 1980) all state the service limit as 11 - 13 kg/cm sq. and in parens say (156 - 185 PSI). None of my Kawasaki manuals have any page designation like the one shown on the top of the page you provided (the number "1-8" in the upper left corner) and none have a section labeled "Service Data" as shown in your picture; all mine have simple, sequential page numbers. What specific manual are you using? Are you positive it's really a Kawasaki Service Manual and not a bogus Haynes or Clymer variety? Ed

I agree, it sounds too high, I looked deeper into the manual and sure enough, they do the conversion in the same section as describing how to run the test -- yours was printed the mid-70s, this is a 1981 model bike though:





The reason this really has me going is that I just did a compression test today on my '81 CSR 650 and I got:

(1) 143psi
(2) 149psi
(3) 150psi
(4) 147psi

I thought, "Great, I'll just go check my shop manual but I'm sure those are good numbers."

Turns out it's the low end of the 'usable range' !!
I'm sure the 'engine warm' psi numbers will be higher, I did the test on a stone-cold motor, 65 degrees ambient temperature today.

I find it hard to believe. It is not a Clymer/Haynes etc. it's a genuine factory shop manual
(see cover above).

That's really interesting! The other thing I just noticed is that they not only raised the top of the compression range, but they also lowered the bottom of the range. So they really expanded the usable range in both directions. I wonder if they changed the numbers as a result of dealers providing them data from bikes actually in use on the road? Ed

At least it is fairly even, so it should balance well enough. Consider a second gauge to reconfirm #'s, also if you do a leak-down test it would show the loss of pressure in percentage which you could formulate to psi #'s. Also a wet test would show the increase in psi that would be from leaking rings.
Those #'s don't sound bad at all to me, for a used motor. Is this the 1 that was Stuck?

Dont be fooled by cold compression numbers on these old cold-blooded, air cooled girls.

Get her good and hot with a swift ride, then check. The difference will be significant!

Also remember that if the compression was low when cold, that it will be hard starting. A motor in good condition should have compression within the service limit, although those #'s from the FSM are "HOT".

To add to the confusion, my Clymer manual :blush: lists three different compression numbers for the KZ 650s:

- 1977-80: 170 +/- 15 psi (12 +/- 2 kg/cm2)

- 1981 : 136 - 209 psi (9.6 - 14.7 kg/cm2)

- 1982 on: 100 - 156 psi (7 - 11 kg/cm2)

Never noticed these differences before, weird indeed.

Motor Head wrote: At least it is fairly even, so it should balance well enough. Consider a second gauge to reconfirm #'s, also if you do a leak-down test it would show the loss of pressure in percentage which you could formulate to psi #'s. Also a wet test would show the increase in psi that would be from leaking rings.
Those #'s don't sound bad at all to me, for a used motor. Is this the 1 that was Stuck?

The 1979 SR kz650 despite many many weeks of atf + acetone is still stuck and will have to come apart. It's my runner 1981 CSR kz650 that I'm running a compression test on. I really wanted to have the engine on the '79 break free so if/when it comes apart I won't have to use 'brute force' to knock it loose, but that's where I'm headed with it. It makes zero sense that my '79 motor would not yield to atf + acetone after all these weeks because the cosmetics are near perfect.
17k original miles on the bike. Gas tank inside looks new. I'm just assuming that the bike got parked in the early 80s and just normal ambient condensation from 30 years' sitting has it stuck. Because this '79 was never parked and left outside -- very little rust at all on it. I live about 40 miles inland from the beaches at Santa Cruz, so I reckon the air here has some sea saltiness to it and might have contributed over the decades to how stubborn this old gal is to come loose.



I'm going to re-run the compression test today on my '81 after a warm-up ride and will repost with the warm compression numbers. 209psi on a stock motor -- man that sounds high. I have had a 4-cylinder early-80s Suzuki at 100psi in each bore that runs like champ, 209psi just sounds like a high-compression racing motor to me, not an old air-cooled 2-valves-per-cylinder LTD-style road bike running 87 octane pump gas.

Just curious as to the Octane recommendation in your FSM with the 200psi compression?

Motor Head wrote: Just curious as to the Octane recommendation in your FSM with the 200psi compression?

Good question, the shop manual doesn't mention octane or gas requirement anywhere I could find, probably in the Owner's Manual which I don't have. I checked the filebase and don't find the OM there, would be interesting to know if they recommend 87, 89 or 91 in this old gal.

Motor Head wrote: Also remember that if the compression was low when cold, that it will be hard starting. A motor in good condition should have compression within the service limit, although those #'s from the FSM are "HOT".

I haven't done my valve clearance check yet, I have put it off with the bike only having 17.2k miles on her, and she starts the moment I hit the button from dead cold. I did buy a new Wal-Mart battery when I got her a couple months back, which helps.

Other thing I noted in the FSM is the carbs are jetted super lean with a 92.5 main for the U.S. model, while the rest of the world gets a 102.5 main jet. I may pull the carbs again and put in 102.5 mains to get a bit more oomph out of it.

I'm going to check valve clearances, but I'm suspecting with the low miles and easy-to-start they will be fine.