Low compression

So I checked compression of my KZ750E-L2. And bad news 90-95-85-85 PSI. The quastion is how to check if it is head gasket, Piston rings or valve adjustment blame for this? I checked valve clearances some time ago and it was all good if I remember correctly. By the way perhaps I could put engine from GPZ?

Did you check it with WOT ?
Pete

Leak down test will tell you where it is coming from if done in a quiet environment. You will need an air compressor/air tank. It puts pressure in the engine so you can listen for where it is coming from. Do search for leak down in the forum to get more info. You can build a cheap leak down test with a quick Google searchm

pete greek1 wrote: Did you check it with WOT ?
Pete

Yes.

With those numbers being so close to each other it's more than likely just normal engine wear.
If one was significantly lower ( more than 15psi off ) then there would be reason to suspect a dodgy valve or piston ring etc.
Probably time for a good overhaul and re-bore .

As kaw-a-holic stated do a leak down test. That will point to the compression leak(s). Check Pep Boys, Advance Auto, and Auto Zone loaner tool programs. At least one of those stores will have or will order set of leak down gauges that you can borrow. Ed

I'm from Lithuania and I don't thin that I have tools loaner near by. I'm thinking of doing the wet compression test and see if the figures will change. Doing that should show me is it valves or bottom end I guess. I thinking it is rings to blame because if it was gasket or valves the compression figures between cylinders will be very different.

650ed wrote: As kaw-a-holic stated do a leak down test. That will point to the compression leak(s). Check Pep Boys, Advance Auto, and Auto Zone loaner tool programs. At least one of those stores will have or will order set of leak down gauges that you can borrow. Ed

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 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!

karoliens wrote: So I checked compression of my KZ750E-L2. And bad news 90-95-85-85 PSI. The quastion is how to check if it is head gasket,,,,

Here's one way to help positively identify the exact point of oil leakage ---

Thoroughly clean engine and allow to fully dry.
Spray foot powder over edges of head gasket, valve gasket, half moons, tach drive, tach drive, exhaust ports, oil cooler lines.
Basically, cover top end of the clean dry engine with white foot powder.
It will appear almost as "painted" white.

Using a flash light or shop light, start the engine and inspect closely for the first sign of emerging oil, which will darken at point of leakage.

Good Fortune!

650ed wrote: As kaw-a-holic stated do a leak down test. That will point to the compression leak(s). Check Pep Boys, Advance Auto, and Auto Zone loaner tool programs. At least one of those stores will have or will order set of leak down gauges that you can borrow. Ed

Using an air compressor hose (rubber tip) option, how much air pressure is safe to use for this procedure?

Am thinking most of the commercial leak-down test kits include 100 psi gauges, but noticed one on ebay with a 300 psi gauge.

Our home-owner's air compressors generally produce 100-120 psi, which is less than many stock engine compression ratios, and should be safe for the poor-man's version of the leak-down test.

Am uncertain about how much air pressure can be reliably held inside the cylinder when hand-holding the rubber-cone-tipped gun into the spark plug hole, before the air starts leaking and hissing back out around the rubber cone tip.

The poor-man's leak-down test can be successfully performed with less than 100 psi, as the idea is to listen for escaping air.
A portable air tank will drop to considerably less than 100 psi when used for the poor-man's leak-down test, yet still provide meaningful results as the pressure reduces.

Would not recommend using a 3200 psi scuba tank for the pressure source. :whistle:

Good Fortune!

My leak down tester zero's at 50 lbs.