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Very low compression after head gusket replacment
- dimanya
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Any ideas?
1982 Kawasaki KZ1000 Police
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- Nebr_Rex
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2002 ZRX1200R
81 GPz1100
79 KZ1000st daily ride
79 KZ1000mk2 prodject
78 KZ650sr
78 KZ650b
81 KZ750e
80 KZ750ltd
77 KZ400/440 cafe project
76 KZ400/440 Fuel Injected
www.dotheton.com/forum/index.php?topic=39120.0
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- Nessism
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Nebr_Rex wrote: Reshim to the correct tolerances.
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Agree. A no brainer.
What was the question again?
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- KZB2 650
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1978 KZ650 b-2
700cc Wiseco kit 10 to 1.
1980 KZ750 cam, ape springs, stock clutch/ Barnett springs.
Vance and Hines Header w/ comp baffle and Ape pods, Dyna S and green coils, copper wires.
29MM smooth bores W/ 17.5 pilots, 0-6s and 117.5 main
16/42 gearing X ring chain and alum rear JT sprocket.
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- SWest
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- 10 22 2014
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Steve
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- Patton
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Could be lack of clearance, and/or issue with mating surface between valve and seat (damage to head or seat, or imprecise valve job, or bent valve), and/or weak or broken valve spring, and/or worn guide, and/or other less common issue such as sticking bucket (for whatever reason), etc.
Would perform a leak-down test to identify where the compression is escaping from each combustion chamber.
A leak-down test injects air pressure through the spark plug hole to pressurize the combustion chamber.
Can perform a poor-man's leak-down test by introducing compressed air into a spark plug hole and listening to where it escapes from the combustion clamber. This may be done at TDC or any other cam positions where both valves are fully closed. Top dead center (TDC) is when the piston is at its highest position. An easy way to tell TDC is by alignment of the T mark with the case mark when viewed through the timing window.
May introduce a spurt of compressed air by using a rubber cone-tip blow gun (rubber air nozzle) held into the spark plug hole. And of course keep holding it in position to keep air from coming back out the spark plug hole while listening for escaping air at other places. The air compressor should not be running while listening because the noise will likely drown out any sound of escaping air. Or just use a portable compressed air tank.
Air heard escaping from exhaust port indicates exhaust valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).
Air heard escaping from carb intake indicates intake valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).
Air heard escaping from crankcase breather indicates loss of compression past rings into crankcase (perhaps worn piston rings or cylinders).
Air heard escaping from head gasket area indicates loss of compression past head gasket (perhaps due to a blown head gasket).
A leaking valve may sometimes be resolved by adjusting the clearance to within specs.
A leaking head gasket may sometimes be resolved by torquing the head fasteners when the engine is stone cold (such as after sitting overnight).
Good Fortune!
1973 Z1
KZ900 LTD
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- Patton
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KZB2 650 wrote: Be sure to read the "how to set valve clearances" thread...... all 125 comments first. :lol:
swest wrote: . . . Did he test drive it before he gave it to you. Was he a HD mechanic by any chance?
Steve
Good Fortune!
1973 Z1
KZ900 LTD
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- Patton
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dimanya wrote: . . . backfiring back into the carbs. . . . .
Indicates failure of the intake valve to fully seal (for whatever reason) when it's supposedly closed.
Often, but not always, remedied by adjusting clearance of the intake valve to bring clearance within spec.
What happens is that part of the combustion inside the cylinder escapes through the leaking (not fully sealed when supposedly closed) intake valve and goes out backward through the intake port and into the carb.
As known:
Good Fortune!
1973 Z1
KZ900 LTD
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- SWest
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Steve.
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- Patton
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swest wrote: A common mistake by an uncaring or just incompetent mechanic it to set the cam timing wrong. If he doesn't have the tool, he will remove the cams then put them back in wrong. I'd first check the clearances. If you're lucky, you can adjust them yourself.
Steve.
Where less lucky, may have resulted in a bent valve due to contact with the piston when the crankshaft was rotated.
Good Fortune!
1973 Z1
KZ900 LTD
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- dimanya
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1982 Kawasaki KZ1000 Police
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- dimanya
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1982 Kawasaki KZ1000 Police
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