Engine CSI

[Continuation of Spark plug CSI: kzrider.com/forum/4-electrical/459321-spark-plug-csi ]

So the bike is a 1983 GPz 550. Spark plugs showed a lot of aging and carbon deposits. Smog reed valves were jammed full of black, carbon deposits. Engine turns, but is stiff.

The next step was measuring valve clearances. the manual gives the spec as 0.004" - 0.008" on the inlet and 0.006" to 0.010" on the outlet. Here are the measurements from my bike:
Cylinder 1: Inlet - 0.004", Outlet - 0.003"
Cylinder 2: Inlet - 0.002", Outlet - 0.006"
Cylinder 3: Inlet - 0.004", Outlet - 0.005"
Cylinder 4: Inlet - 0.002", Outlet - 0.006"

So some of the valves are within spec ... barely. The others are well below spec. What does this mean? Worn valve seats? Can it be fixed?

While I had the feeler gauge out and the covers off, I measured the break point gaps ... not good ... 0.020" and 0.025". Manual gives spec as 0.014".

Those valve clearances are just in need of adjustment. When it's real bad the valves are stuck open with zero/negative clearance.

Change the oil, do a tune-up, set the valves and push the 'start' button.

I'm surprised the bike doesn't stall out when you come off the highway, or on hot days. That's what usually happens when valve clearance gets that low. Yours are not horrible. Probably just normal wear in the valve seats.

Here's a link with some info on cam timing for the 550's.
home.comcast.net/~loudgpz/GPZweb/CamsKZZ...KZZXZR550500400.html
The manual in my signature gives instructions on valve lash adjustment.

Heed the warnings from both sources regarding the valve cover. Don't re-install it without releasing the chain tensioner.


Your bike should have had electronic ignition, not breaker points.

I'm a little confused about valve adjustment if the gap is too small. If it's too big, I can install thicker shims, right? If the gap is too small, can I remove the shims or install thinner ones? Surely there is a limit to this? If so, what happens when it's on the thinnest shim?

loudhvx, yes, it is electronic, my bad. I was measuring the space between the rotating magnetic lobe and the little timing triggers (not sure what to call them) that it passes by.

I finally got a 12mm adapter for my compression gauge and tested the cylinders ... the results are pitiful.

None of the four showed a compression above 30p si! I don't have any oil on hand, so couldn't try the "two tabelspoons of oil and retest" technique, but a shot of PB Blaster in each cylinder brought the compressions up to 40 - 50 psi.

So what do you think? Fried rings and valve seats?

Thanks!

Fried rings and valve seats?

Yes could be that also your valve clearance is too tight...some valve may stay always opened (a little)!

But when having such low PSI in chambers... there should be little resistance when spinning the shaft... unless you have mechanical damage inside the engine.

Btw, be sure your engine is dead cold and cam caps are torqued properly...if not you will have erroneous clearance readings

regards,
laurent

The engine hasn't run for more than a year, so it's as cold as it'll get Haven't touched the cam caps, so they should be fine.

There is resistance when turning the shaft, it goes through periods of more or less resistance through the cycle though. I don't hear any crunching, grinding or grating from the pistons, just smooth swooshes as the move up and down.

How would I adjust the valves to increase clearance? Is there some way to check if they're staying open even when they should be closed?

Was the throttle wide open when you checked compression? Also, you messed around with the spark plugs, did you tighten them?

Did you even try to start the bike yet? You better drain all that PB Blaster from the crankcase first. lol

Yes, you can get thinner shims, and there is a limit. Factory came with 2.50, 2.55, or 2.60 shims. They come in .05 increments down to 2.00 mm. I would assume, if no one messed with the engine, the shims are going to be within 2.30 to 2.50 range, so you will have plenty of shim sizes available.

However, 30psi compression is very damaged. Are you sure the gauge is working? It has to have a check valve to accumulate pressure or it won't work.

I don't think the motor could have even run with 30 psi, much less started. So unless there was some sort of catastrophic break on all cylinders, the engine wouldn't have gotten to a condition like that with simple wear.

I would suspect the gauge is defective. Even with the throttle closed I can get over 100 psi on a worn engine. (The gpz 550's normally are in the 180 to 190 psi range on the multiple gauges I've used.) If you stick your thumb on a spark plug hole during compression, can you keep the pressure in? If not, then it's more than 30 PSI.

Was the throttle wide open when you checked compression? Also, you messed around with the spark plugs, did you tighten them?

Yes he's right you need to WOT all the time you cranked until reached maximum PSI (won't go higher) also all spark plug need to be removed (to help the cranking)... only the gauge connected to the cylinder you are testing.

HTH,
laurent

If you stick your thumb on a spark plug hole during compression, can you keep the pressure in?

Oh and yeah.... stay away from the unconnected spark plug wire...or you may suddenly experience some «little» pain and a «little» F-words!!


Never experienced that :whistle: :whistle: :whistle: :whistle: !

regards,
laurent

ELCouz wrote:

If you stick your thumb on a spark plug hole during compression, can you keep the pressure in?

Oh and yeah.... stay away from the unconnected spark plug wire...or you may suddenly experience some «little» pain and a «little» F-words!!


Never experienced that :whistle: :whistle: :whistle: :whistle: !

regards,
laurent

:woohoo: That'll wake you up.

Yes, actually the coils should have the little yellow or red wires pulled off for this test to ensure no spark. Or at least make sure all plug wires are grounded to the engine. Trying to spark with the plugs out and not grounded will damage the coils or the ignition.