Advice on compression readings...
- ELCouz
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Advice on compression readings...
17 Jul 2010 11:19
Hi,
(bike: KZ750-R1 aka GPz 750 1982)
Before doing winter maintenance in a few months i decided to give a try with the engine compression tester.
I know i need to change the head gasket (little oil leaking at the oil passage on the side and the valve cover gasket)
Check out the readings:
Cyl by number
#1: 150 psi, #2: 121 psi, #3: 156 psi, #4: 145 psi
I put a teaspoon of oil in the cylinder #2 to check the rings.... pressure as increased to 152 psi on the second try... that's mean the rings on the piston #2 are shot ? The bike has only 21 000 miles!
Manual says usable range between 124 - 191 psi and less than 14 psi difference between any 2 cylinders.
What do you think ?
best regards,
laurent
(bike: KZ750-R1 aka GPz 750 1982)
Before doing winter maintenance in a few months i decided to give a try with the engine compression tester.
I know i need to change the head gasket (little oil leaking at the oil passage on the side and the valve cover gasket)
Check out the readings:
Cyl by number
#1: 150 psi, #2: 121 psi, #3: 156 psi, #4: 145 psi
I put a teaspoon of oil in the cylinder #2 to check the rings.... pressure as increased to 152 psi on the second try... that's mean the rings on the piston #2 are shot ? The bike has only 21 000 miles!
Manual says usable range between 124 - 191 psi and less than 14 psi difference between any 2 cylinders.
What do you think ?
best regards,
laurent
1982 KZ810-R1 GPZ with hindle 4-into-1 pipe
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- Old Man Rock
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Re: Advice on compression readings...
17 Jul 2010 11:45
Without accomplishing a leak down test...
run her as is....
Leak down test could inform you maybe a valve seat leaking a tad or so.... If your not blowing smoke, sparkies look good, performance within specifications, she idles, pulls hard etc... again run her....
Just my 2 worthless cents...
run her as is....
Leak down test could inform you maybe a valve seat leaking a tad or so.... If your not blowing smoke, sparkies look good, performance within specifications, she idles, pulls hard etc... again run her....
Just my 2 worthless cents...
1976 KZ900-A4
MTC 1075cc.
Camshafts: Kawi GPZ-1100 .375 lift
Head: P&P via Larry Cavanaugh
ZX636 suspension
MIKUNI, RS-34'S...
Kerker 4-1, 1.5" comp baffle.
Dyna-S E.I.
Earls 10 row Oil Cooler
Acewell 2802 Series Speedo/Tach
Innovate LC1 Wideband 02 AFR meter
Phoenix, Az
MTC 1075cc.
Camshafts: Kawi GPZ-1100 .375 lift
Head: P&P via Larry Cavanaugh
ZX636 suspension
MIKUNI, RS-34'S...
Kerker 4-1, 1.5" comp baffle.
Dyna-S E.I.
Earls 10 row Oil Cooler
Acewell 2802 Series Speedo/Tach
Innovate LC1 Wideband 02 AFR meter
Phoenix, Az
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- ELCouz
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Re: Advice on compression readings...
17 Jul 2010 12:00 - 17 Jul 2010 12:10Leak down test could inform you maybe a valve seat leaking a tad or so.... If your not blowing smoke, sparkies look good, performance within specifications, she idles, pulls hard etc... again run her....
- I'm not blowing any smoke.
- By looking at the spark plug idle seems rich and leaking oil inside all the four cylinders a little bit (valve guide seals maybe...these dries with age) and at WOT mixture is #1 (nearly white insulator just a faint of brown)
- i don't know if it's performance is nearly the same as new... never ridden a bike in 1982 ... jeez i wasn't even born. :laugh:
For the winter maintenance i will have the top end rebuilt (valve seals,valve clearance check, valve lapping if needed) cam chain slack, valve cover gasket and head gasket changed.
I think this should improve a little bit the engine overall.
EDIT: btw, i know it's offtopic but OMR i think you've saw alot of vintage bike in your life... In average how long does these kawa engines tend to last (in miles) before going very major rebuild (crankshaft bearing changed, tranny rebuild etc etc)?
thank you very much!
best regards,
laurent
1982 KZ810-R1 GPZ with hindle 4-into-1 pipe
Last edit: 17 Jul 2010 12:10 by ELCouz.
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- bountyhunter
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Re: Advice on compression readings...
17 Jul 2010 17:11
The factory specs on compression are for a hot engine, not cold and dry. I think yours will be a lot better tested hot. If it runs OK, ride it.
1979 KZ-750 Twin
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- hocbj23
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Re: Advice on compression readings...
17 Jul 2010 17:17
Maw Kaw overengineered these old bikes.Ride em until something major breaks,THEN worry about a major overhaul.Keep the maintenance up, ride sensibly and the bike may outlast you.bj
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- ELCouz
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Re: Advice on compression readings...
17 Jul 2010 22:08The factory specs on compression are for a hot engine, not cold and dry. I think yours will be a lot better tested hot. If it runs OK, ride it.
you are right, make sense to check it while it's hot.
I will do that tomorrow.
Maw Kaw overengineered these old bikes.Ride em until something major breaks,THEN worry about a major overhaul.Keep the maintenance up, ride sensibly and the bike may outlast you.bj
I will do my best to keep her running on the road in a good healthy condition

thanks guys for your help!
regards,
laurent
1982 KZ810-R1 GPZ with hindle 4-into-1 pipe
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- MFolks
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Re: Advice on compression readings...
17 Jul 2010 22:38
I got this from
www.kawasakimotorcycle.org
Kawasaki Valve Clearances
83 Kz1100 D spectre help with valve, emissions, etc
100PSI will light it off , 125PSI will run reasonably well , 150PSI will run well , 180PSI is about a fresh engine.
all readings are cold with a fully charged battery and dry (no oil in cylinders .
Valve adjust can drastically affect cranking compression .
in thousandths of an inch anything less than .005" put the next thinner shim in .
.008" is about the max clearance . .006" if you like to check often . Any less and you risk closing up a valve through inattention and covering up a marginal valve clearance with carb sync , ignition advance and idle adjustment until you actually hold a valve open . Translation ? neglect your valve adjust = $$$ .
Refer to the FACTORY MANUAL for the procedure . Remember to back off the tensioner before replacing the cam cover and replace after the cover is tightened down . Think about that for a moment .
Kawasaki Valve Clearances
83 Kz1100 D spectre help with valve, emissions, etc
100PSI will light it off , 125PSI will run reasonably well , 150PSI will run well , 180PSI is about a fresh engine.
all readings are cold with a fully charged battery and dry (no oil in cylinders .
Valve adjust can drastically affect cranking compression .
in thousandths of an inch anything less than .005" put the next thinner shim in .
.008" is about the max clearance . .006" if you like to check often . Any less and you risk closing up a valve through inattention and covering up a marginal valve clearance with carb sync , ignition advance and idle adjustment until you actually hold a valve open . Translation ? neglect your valve adjust = $$$ .
Refer to the FACTORY MANUAL for the procedure . Remember to back off the tensioner before replacing the cam cover and replace after the cover is tightened down . Think about that for a moment .
1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
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- mark1122
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Re: Advice on compression readings...
18 Jul 2010 05:12 - 18 Jul 2010 05:16
ELCouz wrote:
i would consider, redoing the compression test before u tare it apart. just to verify that it was done right the first time, unless u already verified #2.
things can go wrong during the test. the gauge may not have been sealing properly for example. did u have the throttle wide open during the test? it should be. and redo all cyls with oil as well.
if #2 is still down, it would be nice to address it if u are going to take the head off anyways.
Has the bike ever sat for years unused? u may just have sticky rings in #2. u could try and engine cleaner like Seafoam.
Otakar, has a good eng cleaning meathod as i recall.if u want to do a good cleaning send him a PM.
Good luck
Mark.
Hi,
(bike: KZ750-R1 aka GPz 750 1982)
Before doing winter maintenance in a few months i decided to give a try with the engine compression tester.
I know i need to change the head gasket (little oil leaking at the oil passage on the side and the valve cover gasket)
Check out the readings:
Cyl by number
#1: 150 psi, #2: 121 psi, #3: 156 psi, #4: 145 psi
I put a teaspoon of oil in the cylinder #2 to check the rings.... pressure as increased to 152 psi on the second try... that's mean the rings on the piston #2 are shot ? The bike has only 21 000 miles!
Manual says usable range between 124 - 191 psi and less than 14 psi difference between any 2 cylinders.
What do you think ?
best regards,
laurent
i would consider, redoing the compression test before u tare it apart. just to verify that it was done right the first time, unless u already verified #2.
things can go wrong during the test. the gauge may not have been sealing properly for example. did u have the throttle wide open during the test? it should be. and redo all cyls with oil as well.
if #2 is still down, it would be nice to address it if u are going to take the head off anyways.
Has the bike ever sat for years unused? u may just have sticky rings in #2. u could try and engine cleaner like Seafoam.
Otakar, has a good eng cleaning meathod as i recall.if u want to do a good cleaning send him a PM.
Good luck
Mark.
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
~ ~ ~_@
~ ~ _- \,
~ (k) / (z)
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
~ ~ ~_@
~ ~ _- \,
~ (k) / (z)
Last edit: 18 Jul 2010 05:16 by mark1122.
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- MFolks
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Re: Advice on compression readings...
18 Jul 2010 10:57
Here's a Yamaha product created to free stuck piston rings:
www.amazon.com/Yamaha-Ring-Additive-32oz...-32-00/dp/B002GUCLH2 (Yamaha Ring Free)
I'd try spraying some PB-Blaster in the sparkplug holes,re-install the plugs, and let sit for a few days, then do a re-test before tearing into the engine.
www.amazon.com/Yamaha-Ring-Additive-32oz...-32-00/dp/B002GUCLH2 (Yamaha Ring Free)
I'd try spraying some PB-Blaster in the sparkplug holes,re-install the plugs, and let sit for a few days, then do a re-test before tearing into the engine.
1982 GPZ1100 B2
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
General Dynamics/Convair 1983-1993
GLCM BGM-109 Tomahawk, AGM-129A Advanced Cruise Missile (ACM)
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- ELCouz
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Re: Advice on compression readings...
18 Jul 2010 12:14 - 18 Jul 2010 12:15
For the piston rings stuck... I've ridden my bike for nearly 1000 miles since i bought it... would that release the sticky rings ?
Also, you think beside pressure lost I'm scratching my cylinder walls because rings cannot rotate as they wish?
regards,
laurent
Also, you think beside pressure lost I'm scratching my cylinder walls because rings cannot rotate as they wish?
regards,
laurent
1982 KZ810-R1 GPZ with hindle 4-into-1 pipe
Last edit: 18 Jul 2010 12:15 by ELCouz.
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- mark1122
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Re: Advice on compression readings...
18 Jul 2010 14:30
ELCouz wrote:
well lets not jump to conclusions. it may not be stuck. i'm just suggesting a simple remidy that MAY help IF the rings are stuck, they may not be.
1000miles may or may not release the ring? who knows, did the bike even sit for a long time?
i i dont think u will scratch the wall with the ring. if the ring is indeed stuck,it is not aplying preasure.
For the piston rings stuck... I've ridden my bike for nearly 1000 miles since i bought it... would that release the sticky rings ?
Also, you think beside pressure lost I'm scratching my cylinder walls because rings cannot rotate as they wish?
regards,
laurent
well lets not jump to conclusions. it may not be stuck. i'm just suggesting a simple remidy that MAY help IF the rings are stuck, they may not be.
1000miles may or may not release the ring? who knows, did the bike even sit for a long time?
i i dont think u will scratch the wall with the ring. if the ring is indeed stuck,it is not aplying preasure.

76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
~ ~ ~_@
~ ~ _- \,
~ (k) / (z)
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
~ ~ ~_@
~ ~ _- \,
~ (k) / (z)
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- ELCouz
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Re: Advice on compression readings...
18 Jul 2010 14:441000miles may or may not release the ring? who knows, did the bike even sit for a long time?
around 23-24 years but has been ridden once or twice in the last 5 years (new set of tire and the bike required no carb cleaning starting like a champ)
Also I've rescued just in time this bike from major problem the PO has already let the girl get covered in snow for 1 season.
Back to your suggestions guys, I've put a little bit of PB Blaster inside #2 but i was so excited to test if it would make a difference I've only waited half an hour before starting the girl. After an hour long ride pulled the spark plugs while it was hot like a freshly baked cake

The result are nearly the same for all cylinders +/- 1 or 2 psi.
I will put PB Blaster for a few days in all cylinders and test later if it helps.
BTW, i hear some valve clicking while riding maybe clearance is out of tolerance BUT i don't think it's my problem since i've put a teaspoon of oil in #2 cylinder that increase dramatically the pressure to 152 psi.
any ideas on that?
Wish you a very nice riding season to all!
Regards,
laurent
1982 KZ810-R1 GPZ with hindle 4-into-1 pipe
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