Help With KZ 650 Oil Leak

I have a very low mileage 77 KZ650 B1. It sat for years until this year when I got my hands on it. I have put maybe 700 miles on it this year for total mileage in 32 years of 2,400. I had been noticing a small amount of oil that was pooling around the center stand. It was so small that I thought it was chain or swingarm grease from recent servicing. I went on a 400 plus mile ride this weekend. Before leaving I added about 4 ounces of oil. This filled up the oil level window. I had changed the oil 200 miles prior to this small add. Prior to adding the oil level window showed mostly full but not completely filled. I do not think that I have overfilled. I believe that I filled to the upper end of the recommended range. I just wanted to put this out there in case the collective here believes I have overfilled with oil or if these bikes are sensitive to overfilling.

I noticed after riding 145 miles to my buddy's house and parking the KZ on it centerstand overnight that the oil on his garage floor had grown from a drop or two to a small pool of a tablespoon or so. I viewed under the bike but cannot identify where the leak may be coming from with any certainty. The oil plug and filter cover are tight and free of oil. There is some oil on the backside of the oil filter cover but it seems to be coming from further back. The oil seems to be all along the backside of what I would think is the oil pan. This AM, the oil staining was on the back sideside of the centerstand down position, mostly behind each centerstand leg. Is the the oil pan gasket leaking drippping oil near and/or sending down the centerstand? I have not dropped the pan to change this and am assuming it is the original 32 year old gasket. Any thoughts from my long drawn-out explanation? Is the oil pan gasket the primary suspect? Is the right diagnosis? Please help all. Thanks in advance.

Since you are keeping the oil level on the high side it could be the vent from the crankcase, that would explain why its towards the rear.........Just a guess though

Also, at least my 750 oil pan has a gallery that runs to the back and has a plug in it. This is something else to check. If any motor vehicle sits for years, gaskets get dry and leak. A friend has a 1985 Mercedes Benz with only 2300 miles in it. It leaks.

Paper gaskets don't go bad from age. If it sealed 30 yrs ago, it will still be sealing now unless pevious botched work is there. Primary source of leaks on a KZ650 will always be rubber. 30 yr old rubber is less likely to be bad on a low mileage motorcycle than a high mileage one however. Of course if your filter cover is clean, probably not suspect, but oring around the cover and on the filter bolt. Other possibles are under your sprocket cover theres a plate held with 2 bolts that has an oring, and there are 3 orings between the pan and the engine. All these leak eventually, but in 2000 miles I can't see any of them being bad.

Thanks for all your feedback. Maybe the extra oil is exiting via the crankcase vent. I did not think of this! DOH! My ZRX will do that as well. I have always been very conservative on my oil levels. So, if a little over on the oil level should be no more harmful than just blowing out of the crankcase? Maybe there is some crankcase venting going on.

Side Note: She is running like a champ and since she is just out of the "break-in period", I thought it was time to let her rip. I did take her up to 100mph indicated or about 8,000 rpm on the way down to my buddy's. My riding buddy has a CB750 K model with over 30k on the odo. He rode my bike and cannot believe how smooth and quiet it is. He commented that it runs like new.

I am going to drain the old oil and replace prior to winter storage. I will then be able to better determine the source of the oil. Otherwise I am glad to read the oil pan gasket is not the likely source. Hopefully, I did not blow anything else out when blowing the cobwebs out. All of those rubber O-rings don't sound like fun to dig out and replace. I will check those bolts to see if they are torqued down and for any localized oil leak. Thanks again everyone.

I'd also suspect the crankcase vent.
The rubber elbow that connects the vent to the air box on my bike has a crack and oil does come out of it, but shows up along the bottom edge of the air box (left side mostly) and the frame area below that on the left side.

Forrest, If your're still searching, a couple quick checks for common leaks are, countershaft seal, and airbox. Airbox is easiest, just pull filter and look at bottom of inside of airbox... It's common for bikes which have sat for prolonged periods to stick rings/lose seal.. resulting in blowby thus blowing oil rich vapor back into airbox, where it condenses and eventially "should" drain back into engine via the phlenum cover, old return lines often weep, and could be your' source..If this is the case, don't be overly concerned, as with use/heat cycling they often break free/re/seal.. a c/s seal on the other hand will require replacement. if this is culpret, tis a bit more involved, but at least can be done without engine removal/splitting cases.. luck G

I agree with checking the airbox. Just remove the air filter and see if the inside bottom of box is oily. If so, it may just be a little excess oil being pushed through breather. Ed

Good Morning Everyone! I have read the latest replies and will now go out and check the airbox..........

And the winner is... The crankcase vent!

Initially upon raising the saddle and peering down the inside of the filter, the bottom was bone dry and clean, well except for that dead moth:lol: I then removed the filter screw cap and the filter. Lo and behold the airbox bottom area was wet with oil. There is a raised bottom cup that holds the filter in place. It is as many of you know, raised and fits in a concave area. The oil has been "vented" there and I just did not see when I first viewed with the filter in place.

One more quick question; My ZRX has a rubber tube with a catch bladder that can be emptied when this "venting" occures. I assume there are some rubber tubes for the same purpose on the KZ. I noticed some but may have relocated when I was restoring the bike. Is it possible that there is a kink in the line? Shouldn't the oil pass through one of these tubes to the ground instead of collecting in the airbox?

Thanks again everyone for your feedback and assistance. You are all great resources and help for a poor sap like me!

Tubing should be connected to the bottom of the airbox.

Also, when checking the oil level, be sure to follow the procedure in the manul: Warm up the engine then turn it off, place the bike level on the centerstand, wait a few minutes, check the oil level.