Compression Check

i have had my KZ1000 LTD in my porch for this past winter, basically making it looking nice. last night i dranied the oil and removed the oil filter. today i put in a new filter and added oil. i never took a compression reading on this bike before, but i did today. the readings werent the greatest, at first the first couple where like 70, i kicked the kick starter over a few times more, then they were like 80, 95, 80, 95. then i kicked it over a few times, and a couple off them got a bit higher. does a compression test have to be done after the bike has recentlly been running? my bike was sitting for around 4-5 months, so i was thinking this was the reason. any info will greatlly be appreciated. thanks

i always use the electric start,lot easier to crank her up.did you hold throttle wide open while you did it?if its still low it could just be from sitting and the rings are dry.

thanks for the reply, no i didnt know i had to open the trottle. and i was going to hook up the battery, didnt know if that would make that big of a difference in useing the kick start or the electric start, ill try that to. hopefully the engine is fine, had tons of power and started fine before i parked it for the winter.

It is also recommended that you test it when the engine is warm.

Most manuals don't really explain how to do a compression test; they will tell you to follow the manufacturers recommendations for the compression gauge tool. If you check cold and the bike hasn't run for awhile, compression will be down a little bit... perhaps 5 percent? But the readings won't be all that far off. If you don't check with the throttle open, the readings you get will be pretty much a waste of time. Recheck with the throttle held open. It is kind of awkward to kick the bike and hold the gauge so try using the starter.

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thanks all, ya with the test something is definattly wrong, like i said when i parked it for the winter it had oodles of power, and started with the flick of the switch. i did another test today like i was told, open throttle, hooked up my battery and used the electric start, i let the compression tester get a chance to go up as high as it seemed it would go. still i got low readings from the left side to the right (when sitting on it) i got the following readings 95, 70, 75, 90. i took one plug out at a time, i read someone say to take them all out, then test the compression. but like i said i aint to worried about it, i beleieve its because its been sitting for the last 4-5 months. i didnt touch anything as far as the engine goes since i parked it. i have the air box and filter off it right now, thats about it. so if anyone else has anymore suggestions im all ears, but if not i think ill just wait till spring and drive it around abit, then test the compression. thanks again

fdmc_99 wrote:

...read someone say to take [all plugs] out, then test the compression.

Best method b/c allows higher spin-over and why not (you're removing all of them anyhow).

well i gave it another shot at the end of the day, did it exactlly the same way again, throttle open, with the electric start, this time at least they were all pretty much even, and a few were higher, they went 95, 90, 95,90. and next time i will take all the plugs out at once, and try each hole at a time. thanks all. ive done it like 3 times in less than 24 hours and there getting abit higher, leads me to believe its from sitting for a while

Honestly, the compression you got isn't horrible and I would take the bike out and ride it a week then recheck. Bet it is up to 125 psi or so per cylinder. Try some Yamaha Ringfree. Use it per the instructions. The rings tend to get sticky in the lans when a bike sits. If you put a bit of automatic transmission fluid down each cylinder and recheck, it will also free the rings but give misleading (high) readings as oil tends to seal and not just the rings.

thanks everyone, and ill do that Wiredgeorge, and for reasuring me that the compression isnt horrible, i was reading someone say they had a reading from 160-170, and i was like WOW, something aitn right here. thanks

FSM for 1977 KZ1000 says check compression with engine thoroughly warmed up, all plugs removed, throttle fully open, spin over with starter motor until gauge stops rising.

Standard compression is shown as from 128 to 156 psi (with a lower service limit of 100 psi) and less than 14 psi difference between the cylinders.