Cam chain tensioner maintenance

Introduction

There have been a few reports from club members concerning the cam chain tensioner. On the whole, though, this has not been a big issue for 250 owners. Leon, long-time club member, multiple 250 owner, 250cc speed record-holder, and 12th place (overall) finisher in the 2003 Iron Butt Rally, says not to worry about it: "I've never had an issue with a cam tensioner on the Ninja. In this case, fixing it before it breaks may be what causes it to break. The inside of the engine should be a relatively clean, dry (without water) place. It should be fine where it is. In other words, if it ain't broke, don't fix it."

If you are unsure about this issue, do a search on the board to help you make up your mind. There is a diagram at the Ron Ayers parts fiche. The usual noise for a tensioner getting worn is a loud ticking, similar to noisy (loose) valves. A new one is about $35. Part # for the whole assembly is 12048-1106. Below are instructions for periodic lubing, should you decide you wish to do that.

Camshaft chain tensioner removal

• Remove the right hand "knee grip pad" (side panel). You will most likely find the combination of a 1/4" socket drive, a 1/4" extension, a 1/4" drive universal joint, and an 8mm socket to be the most useful means of removing the mounting bolts.
• There are 2 bolts that hold the tensioner to the crankcase. The tensioner is under pressure from a rather strong spring, so be sure to back the mounting bolts out a little at a time on each side so the tensioner assembly does not become "cocked". Take special care toward the end of the mounting bolts' travel.
• Carefully extract the tensioner assembly while watching for any parts that may fall.

Camshaft chain tensioner disassembly

• Remove the ball bearing and retainer spring.
• Loosen the pushrod locking screw about 2 mm.
• Carefully pull the pushrod and tensioner spring from the tensioner body.
• Remove the ball bearing and retainer assembly and tensioner spring.
• Clean all parts thoroughly with brake cleaner. Toothpicks and Q-Tips can assist with hard-to-reach locations.

Camshaft chain tensioner assembly

• Lubricate the pushrod and tensioner spring with a good quality grease before insertion in the tensioner body. Silkolene Pro RG2 Synthetic is a good choice. Any good molybdenum grease will also work. Assure that any grease you select is safe for use with aluminum.
• You can also pour a little of the same kind of oil you use in the engine into the tensioner.
• It would seem that Kawasaki (in the service manual) neglected to mention lubricating the tensioner before reassembly. So, make sure that you don't skip that part.
• With one hand, squeeze the piston/pushrod and springs into the bore until they bottom out. With the other hand, tighten the set screw until it stops (don't torque it down!). This will hold the piston up during installation.
• Grease the ball bearing and retainer assembly before placing it over the pushrod and pressing it into the tensioner body.
• Slip the ball bearing and retainer spring over the pushrod.

Camshaft chain tensioner installation

• Place the assembly over the crankcase mounting position and insert the tensioner pushrod into the hole.
• Assure the ball bearing and retainer spring and the O-ring remain in place as the mounting bolts are progressively tightened.
• After installation of the tensioner, loosen the lock screw enough to free the pushrod (about 2 mm). You should hear a click as the pushrod releases.
• Tighten the lock screw again. Put a drop of blue Loctite on both bolts.
• The stiff spring in the push rod should now be firmly against the rear cam chain guide.

Cam chain tensioner theory

How the tensioner works: The springs push on the plunger, which pushes on the cam chain. The springs are a specific strength so as to put the correct tension on the chain. There's also a ratchet mechanism in there that allows the plunger to go out, but not come back in under normal use (you can override that for installation).

The negative part of all this is that when the tensioner goes, the cam chain can slap around within the engine, tearing off bits of the plastic that are there to help guide it and protect the metal... which then float around in the engine until they get stuck somewhere or do damage. The chain can also jump teeth, in which case the timing is off and the bike runs terribly, or you have that unhappy valve-to-piston contact. So, if you have a (usually consistent) ticking coming from the upper right side of the motor, and you know the valves to be correct, you should replace the cam chain tensioner.