dumb clutch question

I bought this kz400 (1977) at the end of last summer and rode it a few times before putting it away for the winter. It rode ok then, but I would have to rev it to around 4k before letting out the clutch lever when shifting, especially when starting from a stand still.

Now, as soon as I shift into first, while the lever is still depressed, the bike kicks into gear, lunges forward and dies. I'm sure this is an obvious adjustment problem, but would just like some guidance before I start poking around aimlessly adjusting everything that has to do with the transmission.

Type and weight of engine oil? The "Car" oils sold lately contains friction modifiers to enable the cars to meet the EPA mileage standards for a gallon of gas.

These modifiers are not compatable with wet plate clutches in our older bikes. I suggest replacing your oil with Shell Rotella "T" oil and adjust your clutch to the specs.

A good website for Kz400 twins:http://www.armbell.com/forum/viewforum.php?f=15&sid=9667974e18e4dbde767d35147ce84ee1&mforum=kz400

sounds like the clutch discs are stuck together from sitting. And the cable is a little sloppy.
Try adjusting the cable a bit, and try starting the engine in gear, with the clutch lever pulled in. Hopefully it'll break loose.

Would adjust both clutch cable and clutch push-rod gap.

Loosen cable adjustments at handlebar lever and at mid-cable (near frame downtube by left exhaust pipe), to allow excess slack in cable.

Adjust push-rod:
Remove access cap;
Loosen lock-nut;
Turn in screw until lightly seated;
Back out screw 1/4~1/2 turn;
Tighten lock-nut (snug only);
Replace access cap.

Adjust cable slack:
First at mid-cable to allow final adjusting leeway with knurled screw adjuster at handlebar lever;
Then at handlebar.
Should be able to squeeze lever just slightly before noticing normal stronger pull required to squeeze lever against handelbar grip. The stronger pull is separating the clutch plates (disengaging the clutch) by overcoming the internal springs which hold the clutch plates together (engaged).

The correct push-rod gap allows the clutch to fully engage when the handlebar lever isn't being squeezed. And also allows sufficient cable action for proper separation of the plates when the lever is being squeezed.

After cranking a cold engine, most bikes clunk when first pushing the shifter into low gear, some worse than others. The clunk should mostly disappear after the engine attains normal operating temp.

The push-rod adjustment is to compensate for clutch cable stretch and clutch plate wear.

At some point, a new replacement clutch cable will become necessary.

In cases where the push-rod adjustment fails to resolve a terribly objectionable clunking clutch engagement into low gear, it may help to disassemble the clutch plates and clean them. But that's a later chapter.

Explanatory diagrams follow in the next posts.

Good Luck!

Here's the mid-cable adjuster on a KZ900.

chrispysaki wrote:

...have to rev it to around 4k before letting out the clutch lever when shifting, especially when starting from a stand still....

Doesn't seem so much like a clutch issue, but more like an engine power issue when coming off idle at lower rpm.

Might result from several possible conditions, such as a sticking advancer unit, dirty or mal-adjusted carbs, etc., etc.

Good Fortune!

Thanks, everyone. The push rod adjustment was the first thing I did when the problem happened, and it didn't make any difference at all. I also tightened the clutch cable, and it still happened.

I think I'm going to break into the clutch basket tonight and check/clean the plates and change the oil.