Newbie from NE

ajspellm wrote:

You have any tips on checking the compression? I am going to go buy a gauge tomorrow but am still unclear on what all to do. I think I just hook the gauge up to my cylinder while unscrewing all of the spark plugs but having them against the cylinder so they dont mess the coils up? Or do I just do one at a time and keep the others in while doing this? I am just going to go to harbor freight for my gauge as they have one for like 10 bucks. Will this do?

From KZr Filebase:

Compression Gauge


A compression gauge is a cheap but worthwhile addition to any tool kit. The gauge gives a reading of the
compression in kilopascals (kPa) and/or pounds per square inch (psi). There are two types are available,
one has a rubber cone which must be pushed into the plug hole whilst cranking the engine. This is easy
with electric start but very difficult to do on your own if only kick starting is available. The other type screws
into the spark plug hole and leaves your hands free.

Getting a compression reading it very easy and can be done in a few minutes. The engine should be run
prior to taking the reading, to allow parts to expand and the oil supply to be fed around the engine. Cold
engine readings may not be as accurate as piston and bore will be cold and unlubricated.


Remove spark plugs one at a time and check their condition. Oily plugs will indicate that excess oil
is getting into the combustion chamber due to a worn bore, worn or broken rings, or worn valve
guides and/or valve guide seals. Burnt plugs may indicate a vacuum leak or too lean a mixture.


It is important that the throttle be held wide open whilst taking the readings, to allow maximum air to
be drawn into the cylinder. Loop electrical / duct tape around the throttle grip, and then around the
front brake lever to hold the throttle fully open.


Remove all four spark plugs from the cylinder head but leave them attached to the ignition leads.
Lay each spark plug on the cylinder head so that the metal body of the spark plug is making good
contact with the metal of the cylinder head. This will provide the "ground path" for the electrical
spark and will ensure that the coils are not damaged while turning the engine over with the started
motor.


Attach the compression gauge to one cylinder making sure of a good seal with the rubber cone
type, by twisting into the thread slightly. Crank the engine through four compression strokes (
approx three seconds)


At each compression stroke the gauge will pulse slightly. Make a note of the first and last
readings.


If using electric start, make sure that the battery is well charged.


If using the kick starter, turn the engine just over compression for the cylinder you are
checking, then give several healthy kicks in quick succession.


If the cylinder is in good condition......


The first pulse should be at least 350 kPa (50 psi). This may be a little hard to see if you use
the electric starter.


The last pulse should be within the manufacturers specification. i.e.. between 950-1450 kPa
(140 -210 psi)


The difference between any of the four cylinders should not be more than about 10%. (100
kPa / 14 psi). This third point is more important than the actual figure obtained on the last
pulse. eg Readings of 140, 145, 140, 145 suggest the compression is down a bit and a top
end overhaul may be needed in the next six months. But readings of 180, 180, 175 and 150
indicate a definite problem in the cylinder with the low reading, which should be investigated
immediately to avoid possible expensive problems later

1 of 2 19/10/2005 2:26 PM


If the compression is HIGHER than 1450 kPa / 210 psi, then check the following


Carbon build up on the piston crown and/or cylinder head caused by leaking valve stem oil
seals and/or worn piston oil rings
Incorrect thickness head and /or base gasket


If the compression is LOWER than 950 kPa / 140 psi, then check the following


Gas leak around the cylinder head caused by a damaged head gasket and/or warped cylinder
head
Condition of valve seats
Valve to camshaft clearance. If the valve requires unusually large shims to obtain the proper


clearance, then the valve may be bent and not seating properly.
Piston to cylinder wear
Piston ring and/or piston ring grove wear



If the reading in a cylinder is LOW, then spray a small amount of oil into the cylinder and take a
compression reading again. If this second reading is more than 10% higher than the first reading (e.g. 1st
reading = 140 psi, 2nd reading = 175 psi), then worn rings should be considered. If the second reading
stays approximately the same as the first reading, then worn or damaged valve/s should be considered.

While a compression gauge is a handy tool, a Leak Down Tester is better.


2 of 2 19/10/2005 2:26 PM

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Good Fortune!

I have also noticed that when I start my bike it is very loud. Is this normal? It whines really loud. Not sure if that is my starter going out or what but it is so loud I am afraid I will get my neighbors complaining

Per the factory service manual, the compression test is to be done when the engine is warmed up. A test done on a cold engine will result in lower readings. What you're really looking for is consistent values from all four cylinders within 10% or so.

The whine you describe is interesting. I've heard the starter clutch when it's slipping which sounds like a grinding/scraping noise. Once the engine is running the noise from the starter clutch should go away. There is quite a bit of mechanical noise from these engines with the roller chain driving the cams and such. Without hearing the whine, it's difficult to speculate more.

At idle the mechanical noise is louder than the stock exhaust note.

Thanks for all the help guys. I cant get it running so I wont be able to get a good reading on the compression test. I found a guy locally who is going to look at it and will be picking it up tomorrow or Tuesday. I am not that experienced with the whole thing so I am gonna have a guy look at it and tell me what is wrong. He is charging a lot less then the local motorcycle shop and he seems like a really cool guy so I hope he will explain everything to me about it.

when your doing a compression test you don't want the bike running.

timebomb33 wrote:

when your doing a compression test you don't want the bike running.

I think he meant he couldn't run it to warm it up, and get an accurate compression reading....

I am in Omaha too, and will HOPEFULLY be riding my '81 KZ in a month or two. Lot's to do between now and then! Bikes can be frustrating when you don't know exactly what to check next. Just keep asking questions, searching the internet, and trying different things. You'll get it! (hopefully it's something really simple, and the "cool guy" fixes it for next to nothing for ya)

Got my bike back the other day. It runs awesome now. He said the carbs were all messed up but got them jetted and running perfect. I am thinking now that he has all the adjustments on them right it should run for a while. He also did a few other things that I need and said my rear shocks are bad. Can you rebuild these or do you just have to buy new ones? Are there any aftermarket or what would you guys recommend?
Thanks

Congrats!

Keep a fuel filter inline to keep crud out of the carbs. Run some Seafoam through the fuel system every so often. Drain the fuel and carb bowls when you park it for the winter. If you do those three simple things, it's likely that you won't have to touch them for a long time.

For shocks, there are many options. I know that Z1 Enterprises sells Progressive Suspension shocks and springs amongst many other parts for your bike.