Kz750 Update and Advice needed

Hey all I'm back at it again, here for a sort of update and a bit of advice!

1st thing, i tested the compression 2 weeks ago and the numbers were shit. I'm talking 10, 50,30,85 across my 4 cyc. got a little discouraged. i came across so material to drop about a tsp of oil down into the bike and retest (which is not in the manual i own) and do it again. took the time out today to get this done and thank goodness the numbers jumped through the roof in comparison. 130,150,125,135 so yeas low for the year but seriously from a a to b this is amazing.

i know my next step would be to get it apart and get new gaskets in there, re test and do it all over again. so the advice info i need from whom ever is reading this is just your experience on taking the engine apart and replacing the gaskets, "like do this first and not this as mentioned the manual?" besides the obvious wheel it into the house because the garage is to cold for this madness!

thanks for hearing me out and yes ill take all the luck i can get.

Adjust the valves then try to run it. Once running, the numbers can come up on their own. That is unless you want to take it apart to see what makes it tick. :dry:
Steve

Did you have the throttle wide open when you did the test?
Pete

Oh my!
Adding oil to a compression test can result in very misleading numbers, hence its absence from the fsm. Did you make the dry test with all the plugs out and the throttle wide open?
I don't remember much from the former thread. Did the bike sit outside unridden for an extended time? If so, the rings may be stuck. It could also be sticky valves or a cam out of time.
A leakdown test will be more revealing than a compression test in terms of determining where the problem is.

I really doubt if gaskets are the problem. If the head gasket was leaking that much, you would be hearing a loud whistle, wheeze or hiss every time a piston came up on the compression stroke.

If the bike has sat for a long time you can not do a proper compression test because the rings may be sticky. The engine needs to be hot and the throttle held wide open to do a proper compression test too.

Some Marvels Mystery Oil in the cylinder will help loosen up the rings if the bike has sat.

Adjust the valves and get the bike running, then put a tank or two through while performing an Italian Tune Up. Once you do that then do your compression test again.

thank you all!

yes i held the throttle wide open while testing the compression before and after adding oil, with all the spark plugs removed. The Bike had defiantly been sitting for a while it is a barn find so it sat for the past 3 years there and thats as much of the history the fellow i bought if from had on it. i didn't hear any whistling noise that i can tell, so ill keep running with that bonus . i would love to avoid taking the engine apart to replace gaskets, so valve clearance is defiantly an easier route, i will start there.

will the standard 10w40 loosen up the rings, or shall i be picking up some mystery oil on payday?

Just to make sure i understand:
Adjust the valves and try to get it running then rates the compression again correct. otherwise my number are shitty either way.

also what in the world is an Italian tune up?

What Nessism is suggesting is to pour a little Marvel Mystery oil into each cylinder and let it soak for a day or two. It might help loosen up the gunk that is keeping the ring from doing their job. Any name brand 10w-40 motorcycle specific oil (JASO-MA) is good for the crankcase. As for the Italian tuneup, I guess he could mean to eat a plate of lasagna and ride it like you stole it! :woohoo:

TexasKZ thank you, i will not use any more of the 10w40 mc oil i have and drop in some MMO when i go grab a bottle next. thank you all seriously and ill defiantly be back in the mix once that portion of the process is done... And believe me when i get him on and running i will defiantly be riding like i stole it!

Thanks Again

They have MMO you can put in the crank case. Might be worth a shot. Ride it for a while and see if it improves.
Steve

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!

If you are going to be putting oil in your bores to let it sit with a view to freeing your rings, make sure you crank the engine over without the plugs in to get rid of the oil before you put your plugs back in permanently and think about starting it or you could damage something with the "hydro locking" effect of having cylinders full of oil.