'78 KZ650 Leaky

Hello all,
I recently acquired a 78 KZ650 with a Wiseco big bore kit (709cc now if I remember correct) and have been absolutely loving the bike.

The previous owner (a very capable mechanic) rebuilt the motor with the big bore kit and has been running it for approx 2-3K miles before I bought it. Reading through the forums it sounds like the KZ's seem to have some funny spots that like to leak oil, and this bike is no exception.
After my commute home 20-ish minutes and giving the old gal a good romping (not too bad, dont want to break a hip), I get home and park and always have a drop or two of oil on the floor.
While not a good thing, is this necessarily a bad thing? A bad omen, a sign of trouble in the future? Or is it just an indicator that he had no knowledge of the leaky quirks and where to direct more attention?

I should also note that the crank case breather filter is wet with oil after a ride...he added an oil cooler to the bike, so I would guess that if when trying to compensate for the oil cooler volume he may have over filled with oil, resulting in excess leaving via the breather? Is this sound logic?
Where else should I check and/or reseal (liquid gasket 1184?) that is prone to leak? The black half circle rubber pieces on the top end, tach cable input,...?

I've done quite a bit of searching, but its a lot of info to seek out in small snippets of info...that and Im new to the KZ as well (first bike!). So please show some mercy
Thanks guys!

Where does it appear to be leaking from, which side, or front or back of engine?

If you have leakage from the tach drive you should just replace the little pieces needed; they're available and easy to do. If the cam plugs are leaking I would also replace them. Trying to plugs leaks with sealant is a lost cause that will not last long. You should check the oil level using the little site glass on the right side of the engine; if it is overfilled it will cause oil to come out the breather. If you don't have a Kawasaki Service Manual you really need to get one; it makes owning these bikes much more enjoyable and affordable. Also, if you aren't aware of the JIS screws please read the link below. Ed

kzrider.com/forum/21-tools/532335-budget...ewdriver-tips#532335

There are 100 rubber o-rings on a KZ650 as well as the half moon cam end plugs. Any and all will eventually leak. Mostly on high mile engines that have seen a lot of prolonged heat. The rubber used back in 1978 was not all that great when subjected to high temps. A couple drops of oil though is nothing to worry about unless you're a perfectionist. To me oil leaks are mostly cosmetic, if the bike is not all that great looking, I could care less myself. I rode my 77B1 today, the ugly one and got oil on my boots from the thing leaking and only rode 20 miles. Fixed the problem by wiping my boots and the engine with a paper towell. I'm not ever going to be in the mood to pull another head to change leaky orings. Oil leak? Who cares is my feelings any more in my lazy old age. Now if it's a mint condition bike with original paint like Ed's 77C1 then I would for sure fix any leak. Otherwise just ride and enjoy.

Thanks for the replies, everyone!
Last night I gave the motor a good cleaning so that it would be obvious where the leak was coming from, and after this mornings ride in to work, its quite obvious. The oil appears to be leaking either from the (head gasket? Where the case and juggs meet) OR from the cam chain tensioner. I should also note that the tensioner doesnt appear to have a proper gasket in use, it looks as if it was sealed up with liquid gasket of some sort. How bad of a time am I going to have trying to replace that gasket? Or will I be able to finaggle it over/around the part without completely removing the tensioner?

Ed - Thanks for the tip on the sealant, I get the impression that it doesnt do much good on these bikes. Also, after you mentioned the JIS screws I didnt recall actually seeing them on my bike..looks like the previous owner used the kit from Z1 to swap them all out to socket cap head fasteners. :woohoo: One less Japanese snafu to deal with. Those JIS looks strange though, kinda remind me of posi-drive.

Ron - My bike saw a cafe conversion (not everyones cup of tea, I know), so OEM and orig. look is not a terribly large concern for me I took your approach and simply wiped off my boot. Haha.

Oil check shows 2/3 to 3/4 level (between measurement lines on window), previously was over the top line which would probably explain the saturated breather filter.
Finally, I also noted last night that the plugs the previous owner put in were one step hotter than the Normal range recommended by the Clymer manual. Is this related in any way to the overbore kit, or should I follow with my plan to replace with normal temp ASAP?

Again, thanks everyone for fielding my questions. while I am pretty mechanically inclined, bikes are a new world to me and Im trying to figure out each system one at a time.

Regarding the plugs - I believe the Clymer books may have copied an error from the first edition of the Kawasaki Shop Manual. The error is that the 1st edition called for NGK B8ES or ND W24ES plugs. These plugs are too cold. Later Kawasaki Service Manuals corrected this error and now call for NGK B7ES or ND W22ES-U plugs; these plugs work much better for street use. Ed

Ed, my Clymer actually calls for the B7ES, those I will be picking up after work today. Currently the bike has B6ES plugs on it, but could this be due to the big bore kit?

Alright, so I finally got around to giving the motor a really good cleaning and identifying where the oil is coming from. Unfortunately, it appears to be seeping from the gasket where the case and jugs meet, right below the cam chain tensioner on the aft side of the motor.

At this point, Im not exactly sure if it's kosher to keep running this thing and rebuild after summer, or if its just going to get worse. Oil level is okay, I've been keeping it towards the high end of the window.
And after a 20 minute ride on the freeway I park her in my garage and she'll drop a couple drops on the garage floor, nothing terrible, really.

So what do you guys think? Will she last the summer or should I start ordering gaskets? In the case of a rebuild, as the motor only has about 2K miles on it since being rebuilt, can I literally just disassemble enough to install new gaskets and reassemble without any major adjustments (valves and such)?