Proper Cam Chain Tension & Adjustment

"HAPPY NEW YEAR EVERYONE"

While the 82 XJ650G has a cam chain adjustment via the cam chain tensioner, the (82 XJ750J )model is supposed to be equipped with the automatic cam chain tensioner, and supposedly no adjustment is necessary?

With the cam cover off, the cam chain can be seen supported by a CAM CHAIN GUIDE in the middle between the 2 sprockets. Does this cam chain guide also play a part in the proper can chain adjustment?

What is the proper clearance measured, or looseness felt, by pulling UP on the chain from this chain guide? Should one be able to measure about 1/4" clearance between the top of the center of the cam chain guide and the bottom of the chain that rides on top, by manually pulling Up on the chain with your fingers?

pulling up on (CAM CHAIN) with fingers
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About (1/4") clearance between (CAM CHAIN) & (CAM GUIDE)
________________
(CAM CHAIN GUIDE)


How do you measure proper cam chain tension if possibly the automatic cam chain tensioner is not working? Or, how much free play and looseness is acceptable measuring this way?

If this is the case, where is the auto tensioner located on the outside of the engine, to take off and see if the springs and cam inside the cam chain tensioner itself are not broken and working properly?

Thank you for any advise or suggestions!!


Bob

 

In my experiences the cam chain is barely moveable up from that guide. Tensioner is between/below the carbs. Unlikely the thing is broken (not really much to break) Perhaps you could try this: As you have the V cover off? Rotate the Intake can shaft (using the cast in hex and a wrench) perhaps a 1/4 Turn clockwise (not v much at all) ie: towards the Carbs This in an attempt to tighten the chain between the Crank sprocket , the Ex cam sprocket and the Intake cam sprocket.. Thereby putting all (if any) chain slack into the run between Intake sprocket and Crank sprocket..where the Chain tensioner is supposed to remove it. You MAY have to lock the Intake cam (vise grip.. v carefully!) as the Valve springs will want to snap it back towards the Ex cam.. rendering yr effort to take out chain slack wasted.. and you have to try again.
Once satisfied that you have gotten all the slack behind and below the Intake cam sprocket. (Make SURE you do not rotate any of the sprokets untill the tensioner bolt is back doing it's job.) THEN loosen the Tensioner bolt (on it's side) watch the tensioner spring forward to take up the chain slack.. then retighten the tensioner bolt. Job Done.
IF that does not tighten yr chain slack to your expectations.. you get to buy a new cam chain... approx $40 and a lot of swearing trying to thread in the new one..

 

Danilo,

With some 89 ppl viewing that posting, I'm sure I'm not the only one that could learn something from your reply. I do thank you for your time and the details you put in to explain the process.

I do understand what your saying by trying to take the slack out of the cam chain by moving it down toward the crank where the tensioner can then take it up. Had you experienced this first hand before, or did you just reason it out from your knowledge of it's workings?

Thank you!

 

The Timing Chain should be fairly tight across that Guide Bridge. If you can lift it off. it's time to investigate why.

If your Bike has more than 50,000 Miles ... replace the Cam Chain.

If you have appreciably less miles on the Machine ... do a Manual Tensioner Adhustment.

Remove the Spark Plug.
Remove the Left side Crankshaft Cover.
Note the Square Flats on the Ignition Rotor.

Using a suitable wrench ... Rotate the Engine two full revolutions in the direction the Crank rotates when the Engine is running.
Bring the Crank to a slow and gradual stop.

Then:

Quickly reverse direction on the Crank ... rotating the Crank OPPOSITE its Normal direction when the Engine is running.
This will present the Slack in the Chain to the Tensioner as the Chain runs in reverse ... coming off the Crank Sprocket up to the Intake Sprocket.

As the slack is presented before the Auto-Tensioner ... The Tensioner will move itself to take-up the slack not normally presented during the rotation of the Engine as it is running.

The Tensioner may need a small amount of persuasion.
Tap lightly on the Hex Bolt at the rear of the Tensioner with the wooden butt-end of a hammer handle.
(Have and assistant do this for you ... continually ... as you do the Manual reset maneuver.)

Once the Tensioner moves-out to take-up the slack ... the adjustment is done.
Do the maneuver several times ... rotating the Engine two full Revolutions in its Normal direction before reversing direction to insure that all the slack is removed.

 

Rick,

You never cease to amase me! I always like to read your advice and insight into any problem one might have. Your complete details of what, where, how and why make things so visable one can only say; Gee, I wish I would of thought of that. I guess that is what makes you a good teacher, while we are all trying to benefit from that knowledge.

Thanks again my friend. One can never learn to much of a good thing!

Bob

 

Interesting Method Rick... But I'm not a fan of that method.
I Bent 4 intake valves on my Alfa years ago using that precise mehod (which in fairness was the Proscribed Method outlined in the Garbage Haynes Manual) A costly mistake, I have thankfully ..not ever.. repeated, on 'many' twin cam engines in the subsequent 25 years.
Again I suggest do ALL chain tension ing adjustments V carefully. ..No need to spin the crank twice unless you just like doing so.
Problem is: as mentioned/alluded to before.. the Valve springs will force the Intake cam to.. Rotate, Forward normally .. Taking up slack instead of the adjuster.(overpowering it basically. The Valve springs are a wee bit beefier than the Tensioner one . Basic problem is: the adjusters on these engines are Poor designs (cheap?) (Real ones.. in better designed engines) have a ratched pawl to prevent them from being forced back wards. a small but ..crucial.. improvement/advantage.

The procedure that I outlined is the only one that I use ..or would even think about dispensing.. It works.. mostly, fool proof.. even with Beginners.

 

Rotating the Engine in it's opposite direction to present the slack before the Tensioner is the method in Haynes and the Factory Manual. I think they want you to rotate the Engine through two full revs to insure that the Chain moves within the Engine far enough for the slack to move over to the rear side so that rotating the Engine in the reverse direction allows the front side of the Chain to come-around back for the Tensioner to take-up its slack.

I don't know of another method.
I'v been doing it "By the Book" since day one.

 

The auto adjuster has a cam that grabs and prevents it from reversing. Of course the manual tensioner won't back out unless you unscrew it.

Bending valves (whichever direction you turn the engine) is an indication of something more serious than a little slack in the cam chain.