Clutch Slipping, or Oil to blame? (79 KZ650SR)

Be careful using that 1977 manual because there are major differences between the 1977 KZ650 and other models. One totally different system is the charging system - the 1977 is not at all like other years. Ed

Thanks! I've read about that elsewhere - telltale signs like the 3-bolt side covers and such, pointing to big differences... this is why I referenced the pictures as a guide, and only for the clutch. If someone's got a link to a 79KZ650SR manual, I'm all ears (er, fingers, as the case may be). I'll continue my search for a proper service manual for my bike in the morning.

Side note: "Colton's Garage" on YouTube has a young man who gets a KZ650 and finds his bike is probably a mishmash of parts from different years (engine, frame, electronics) ... somewhat entertaining for us KZ fans.

This poor bike has been plagued with issues since I got it in 2017... the highlights being leaky forks, a faulty rear brake light switch (that blew fuses, killing the whole bike), leaky petcock (and it's the one that can't be rebuilt with the available kit, so my bike has a KZ1000 petcock on it), carbs all out of whack, a bad cush drive?, now the clutch, and something that causes it to idle at 2,500 RPMs when fully warmed up (10 miles or so into riding), but won't start if I set the idle screw to 1,200 RPMs or so. It also requires the petcock to be on prime for 10 seconds after sitting for a week for it to start. Oh, and it had leaky carb holders and intake boots. It also had a "knocking" type noise at idle, but the recent oil change seems to have made that go away - I haven't noticed it at all since I changed the oil.

Of these issues, the only remaining ones are the intermittent clutch slippage, cush drive, idle, and starting issues. I've had the rest replaced or tuned.

-John

drakhen99 wrote:
If someone's got a link to a 79KZ650SR manual, I'm all ears (er, fingers, as the case may be). I'll continue my search for a proper service manual for my bike in the morning.

I can offer you a 81KZ650 D4 Manual. The clutch release adjustment is nearly the same task.

With this adjustment you only need to use your thumb and forefinger until it stops then turn back the designated amount.

40 year old bikes require a lot of maintenance. Adjusting the clutch, and/or replacing the springs, are just one of many tasks you shouldn't be shy of. The factory manual details out a lot of the normal routine maintenance, such as valve adjustment, that must not be neglected. All good fun and part of owning a vintage machine.

www.kzrider.com/modules/ServiceManuals/K...l%20KZ650%201981.pdf

www.kzrider.com/modules/ServiceManuals/K...Service%20Manual.pdf

The factory manual will be a priceless tool. Yes, the one for your specific model will be best as Kawasaki made some significant changes along the way.
When adjusting the clutch cable, it is important to follow the factory procedure.
I agree that the most likely causes are the cable adjustment and the springs. The clutch itself is surprisingly robust, and will last many thousands of miles unless it has been subject to a lot of drag racing or abuse.

I think I'm gonna need a house with a garage! With 2 little kids soaking up their fair share of my time, projects that take more than an hour or so, usually end up taking several days. I'll tinker with the clutch adjustments and if that doesn't fix it, I guess I'm ordering parts to do a clutch swap - is there any sense in not replacing the clutch pack if I'm gonna do springs? Or even the cable, at that point?

-John

Here a re a couple of tools that will make you maintenance easier.

The cable lubricator allows you to insert the spray tube from your lube spray can into its body, thereby directing the spray into the cable instead of all over the bike.

www.z1enterprises.com/yamaha-xs650-cable...ubrication-tool.html

All of those screws on your KZ look like Phillips heads, but they are not. They are JIS cross-heads, and a Phillips screwdriver can really mess them up if they are tight.

www.z1enterprises.com/screwdriver-jis-se...hree-1-2-3-html.html

Thanks for the link to the screwdrivers! I already have (and used yesterday) a cable lubricator.

My tool set includes a #2 (I think) JIS bit - I used it to take the clutch adjustment cover off yesterday.

-John

If the cable is showing signs of rust, or if any of the strands are starting to fray, or if it is too stretched to adjust properly, replace it.
As I mentioned, the clutch plates themselves are likely ok. If you are concerned, I recommend measuring a couple when you open it up to replace the springs.

Here's some KZ650 generator info from another member...........



Ed

Quite a few times I've experienced a slightly slipping clutch after an oil change. It was always because of slightly overfilling the oil. After correcting the oil level it would take quite a few rides before the clutch would stop slipping. The 550 manual even warns of this exact problem.