'79 KZ650 Top End Gaskets and Seals

Hi everyone, I have a '79 KZ650 thats leaking oil from what looks like the head gasket. I'm fairly new with bikes and have no idea where to start with replacing the head gasket. From my understanding there are serious risks to taking the engine apart without knowing what you're doing and so I'm looking for any sort of guide or guidance for undertaking this.

I do have an owner's manual, and I've seen the "kz650 top end reassembly" playlist on youtube, as well as a black and white walkthrough on how to rebuild the top end. I think all 3 of these resources are far too in-depth for what I need to accomplish. I have taken the engine out before, though from my understanding the engine can remain for top end work. I figure while I have the top end semi-apart I might as well replace all the gaskets I can without going to far down the rabbit hole and I've stumbled upon a few different sets, any advice on whether or not one of the three of these are worth buying? My biggest concern is that I see head gaskets for a kz650 selling upwards of $100, any dummy would second guess a whole set of gaskets at near or below the price of a single head gasket so what am I missing?

Here are the sets I'm considering:
z1parts.net/kz650-complete-gasket-set-1979-1980/
www.z1enterprises.com/gasket-set-kz650-79-80-top-end-kit-2.html
www.z1enterprises.com/gasket-set-kz650-79-80-full-set.html

If anyone has seen a guide that I can't find or could point me in the direction of the right forum post that would be a huge help as I'd really like to have this sucker ready for the spring

Before going any further it would be good to make sure the head gasket is actually leaking. I've owned my 1977 KZ650 for 42 years (62,000 miles) and the head gasket never has leaked.

What is sometimes mistaken as a head gasket leak is simply a leak where the tachometer cable attaches to the cylinder head. I suggest you clean the area very well and then see exactly where the oil is coming from. If it appears to coming from the area near where the tachometer cable attaches to the engine that is probably the source of the leak, and the good news is that it is easy and inexpensive to correct.

One other thing that may contribute to leakage is old oil that has broken down. When is the last time the oil was changed and exactly what oil was used? The wrong oil can cause problems. Ed

I would second 650ed response. The tach o ring fails and is a easy fix. Clean and run the bike . The valve cover gasket would be another culprit.

OEM gaskets and seals are best. You can find the part numbers from a site like Partzilla and then search ebay for a good price.

When tearing down the top end it's best to go all the way to the engine case. That way you can replace the base gasket. When removing the head the clamp load on the base gasket is released and that's not a good thing with 40 year old gaskets. Also, it's best to replace the valve stem seals and lap the valves. Yes, the entire process is not as simple as just replacing the head gasket, but after you are done the engine should be oil tight for years to come.

Wow I feel like a dummy, I removed the tach cable as I didn't want a tachometer and jerry rigged a seal - sounds like thats exactly what the problem would be? I never would have thought that, I guess I'll search around for a proper tach seal and then run the engine before tearing everything apart. Thanks for this, what a huge help

Great advice searching through ebay, I never had high hopes for these aftermarket sets. I'm hoping its the tach seal but I'm thinking I'll replace the seals you mentioned because I have the time.

Thanks for the help, also wish I had seen your 750 project before I stripped and painted - it would've been much easier.

In case the tach seals don't cure the problem, be advised the KZ650 uses probably between 50 and 100 other rubber orings ect for seal of various parts. There are multiple orings between the oil pan and main cases, orings on various oil gallery plugs, ect. Orings for a cover that covers the transmission shaft, of course the rubber camshaft end caps, the oil filter oring, orings between the head and cylinder, between the cylinder and cases.
They are all 40yrs old, and back then there was no good rubber available that could withstand heat coupled with age. Gaskets wont leak, but the rubber does, and it happens a lot. My first leaks started at 10,000 miles, and most have been many times repaired and they will come back. As much as I always loved the KZ650, it wasn't the best design in the oil tight department. Rubber, too much rubber. The KZ1000 hardly used any rubber in comparison. I don't know why they made the 650 the way they did, but that's life.

There is a tach block off available from Z1 Enterprises, fits the 650.
www.z1enterprises.com/tachometer-drive-b...kz900-z1-kz1000.html