Cam Chain Tensioners

Cam chain tensioners for Z, KZ, ZN and ZG 1300s (more information needed regarding ZG models)

In an 1985 article ClassicMechanics.com described the evolution of Kawasaki automatic cam chain tensioners. I've excerpted the portions of that article applicable to 1300s article here.
The first automatic tensioners fitted to the 1300s consisted of a spring-loaded plunger that advanced to take up any slack in the cam chain. The plunger was prevented from backing off by a ball race that fit within a tapered cone. Wear with this design could be seen as tiny tracks in the plunger where the plunger vibrated against the ball race. These tracks could cause the plunger to retract as the ball race failed to properly grip the plunger. Any grooves or tracks in the plunger should alert the owner that a new tensioner is in order. Some of these ball race tensioners had a pinch bolt that was intended to hold the plunger back during installation. The procedure was to install the tensioner with the plunger secured in the retracted position by the pinch bolt and then once the tensioner is installed, loosen the pinch bolt to allow the plunger to advance, taking up any slack in the chain. Inventive owners found that it was possible to replace the pinch bolt with one that was somewhat longer. This longer pinch bolt could be used to secure the plunger preventing any advance or retreat, in effect converting it to a manual tensioner. However, not all ball race tensioners had the pinch bolt.

These ball race tensioners were fitted to the 1300s from ’79 through ’82. The ’83 ZN1300 still had a ball race tensioner but this one was backed up by an external oil line. This ‘hydraulic’ tensioner incorporated a check valve within a banjo type connector to prevent the oil from flowing back into the engine thus backing up the plunger hydraulically.  As I disassembled the tensioner on my ’85 ZN 1300 I found the rubber supply hose to be empty which means that the hydraulic backup portion of the system may well be delayed at start up until the oil pressure fills the hose and forces the air in the tube through and into the engine. In the last 10 years we’ve heard about 6 or 8 engine rebuilds required due to bent valves. While the owners didn’t claim “My cam chain tensioner failed”, we would directly relate these disasters to tensioner failures which caused either a loose cam chain to wear the nylon tensioner sprocket, or beat the nitrile rubber off of the tensioner roller, either failure would allow the cam chain to get slack enough for the timing to jump.  No one has reported a failed timing chain. If you have personally experienced a cam chain tensioner failure of any magnitude on a 1300 please let us know.

Ball Race tensioners: Maintain, Repair or Replace.

All the 1300s incorporated a ball race tensioner. The ZNs have the added oil line backing up the ball race with engine oil pressure. We’ve described what wear should be looked for when examining ball race tensioners additionally we’ve discovered that the oil pressure back up system will not immediately provide oil pressure during startup. While I wouldn’t say that this delay is a failure, it is a weakness. I can imagine a momentary situation where without the supporting oil pressure at start up the ball race slips and allows the plunger to retract resulting in bent valves.Given the poor reputation that the ball race design has and the momentary delay that happens before the oil pressure provides support on the ZNs (data needed on the ZGs) we think all the cam chain tensioners on 1300s should be replaced either by:
1) modifying a stock tensioner with a backup bolt, or 
(2) replacing the stock tensioner with a ZX11 tensioner modified with a lighter spring and a backup bolt or
(3) installing a manual tensioner and performing regular scheduled maintenance.

Comments on manual tensioners.

The market is awash with manual tensioners some manufacturers provide instructions on how to adjust them, some provide nothing. With an automatic tensioner the spring and oil pressure put a constant tension on the system. How much pressure is needed? The answer is: enough to take up any new slack and no more. The rub is any new slack.  There are a number of vulnerable parts in the cam chain management system including: the chain, the nylon toothed tension roller, the nitrile tension roller and the various plastic guides.  Too much tensioner pressure will cause premature wear of all these parts. (Footnote1) Hopefully the designer has figured the proper amount of pressure. When we assume the role of designer by substituting a tensioner from another machine we’re pretty much on our own. A lot has been written about refitting the tensioner from a ZX 11 onto our 1300s, most authors say the spring from the ZX11 is too strong and needs to be shortened by 10mm. The problem is the shorter spring, when compressed the same amount, as the longer spring gives more pressure. The unknown is how much to compress the shortened spring. Since I’ve not taken the time and effort to test the eventual pressure, I’m shying away from the ZX11 tensioner substitution.
Alternately, a properly adjusted manual tensioner puts no pressure on the cam chain.
How do we get to minimal slack with no additional pressure? (Footnote2).
Remove the ground lead from the battery. Remove the spark plugs. Remove the cover over the wiring to the right side alternator remove the right side alternator. Rest it on something that will allow it to be set aside without stressing the wiring. Turn the crank shaft clockwise, with a 17mm socket, until the “T” mark aligns with the seam between the upper and lower cases at the front of the engine. Remove the existing tensioner. Take another look at footnote 2 !  Adjust the tensioner plunger/bolt by hand until you feel it contact the tensioner inside the engine. The contact will be firm, you are turning the plunger/bolt by hand, right?  Now back off the plunger/bolt 1/6 to ¼ of a turn and tighten the locking nut.
Since stretch on a chain is not even all the way around the chain subsequent adjustments can be performed on a hot running engine (take another look at footnote 2). Adjust the tensioner by ‘feel’ as you minimize the slap of the chain and then back off as previously described and tighten the lock nut.

Footnote 1: A worn beyond the service limit cam chain will alter the camshaft timing by as much as 10 degrees just for the camshaft drive chain. The wear on a secondary drive chain will also add to this camshaft timing issue retarding cam timing which drops engine performance. Intake vacuum gets worse (less) leading to almost impossible carb adjustments.

Footnote 2: Never rotate the 1300 engine, even a little, without the cam chain tensioner fitted. The cam chain could skip teeth and bend valves.

Well written !

The "common" approach in dealing with the ZX10's stiffer spring has been noted as shortening it.  This is incorrect !  Doing so increases the springs pressure applied to the rubber-roller and sprocket.
Google Search: "Why Shortening a Spring Increases Tension" 
 

Thanks Scotch,
It was a joint effort, Kawboy and myself. It's intended as a starting point.
Regards
Bill