cam chain adustment

Dear forum, I saw a note on adjusting the cam chain on another post and I think this is what is needed on my 82 650 Seca. Just rebuilt the carbs and I now have a rattle coming from the engine that wasn't there before. I've also been working on bringing back a 72 XS650 using the 650 Garage forums so I'm sensetive to cam chain adjustments. As this is the first 4 cly. bike I've ever owned or ridden I'm kinda at a loss as to the procedures. thanks for the help and keep up the good work with this forum.

Terry Monday
Jacksonville, Fl.
72 XS650
73 BMW R75/5
78 BMW R100 SRS
82 650 Seca

 

Your Seca has an automatic cam chain tensioner. It's possible it stuck, but unlikely.

If I'd just had my carbs off and got a rattle after reinstalling them I'd look for something loose or out of place that is rattling. Also possible you've got pre-ignition. You sure you're not way lean?

 

Well, ... it can't hurt ya to do a Cam Chain Tensioner reset. Why not? It either is or ain't the Cam Chain you're hearing ... and I'm with MiCarl doubting that that's what it is.

You might have the Mixture too Lean as he suggests, or ... you might be "Listening" to the Engine in a different way than you did before doing the Carb job.

Pop the left side Crank cover and wrench the engine over backward.
That's going to let the Tensioner grab any slack if there is.

You might be hearing the Cleaned Carbs delivering a weak mixture and be experiencing pre-ignition.
A quick look at the Plugs will solve that mystery.
Way too clean ... way too Lean!

Then, again ... your EAR might be listening for Mixture related changes in the exhaust note and you're hearing a noisy Valve Train rattling as the Valves open and close while you are trying to detect a Mixture to feathered-out or too Rich.

If you think it's serious enough to worry about ... "Probe" the engine with a narrow wooden dowel and listen to the mechanical sounds.
Isolate the noise.
Determine what it is!

 

Pop the left side Crank cover and wrench the engine over backward.
That's going to let the Tensioner grab any slack if there is.

could you just put the bike in high gear and roll is backwards?

 

I used these instructions from a old post to adjust my cam chain tensioner. Worked great, got 2 CLICKS, and all the noise went away.....took maybe 10 min start to finish.

Posted: Mon Jul 30, 2007 5:02 pm Post subject: Re: Restting cam chain tension

--------------------------------------------------------------------------------
No Pix.

Automatic

Manual Re-set.

Manually rotate engine two full turns Clockwise coming to a smooth and steady halt.

Quickly reverse direction placing any Chain Slack in front of the Tensioner.
If it clicks.
You reset it.
If it don't ... try the procedure again.
If it clicks.
You reset it.
If it don't ... it didn't need too ... it's automatic.
_________________
Rick Massey
Moderator - Tech Writer

 

pop the cover off, turn the rotor until the C mark is aligned, Then loosen up the 12 mm nut that is on the 10 mm headed screw. Then loosen up the 10 mm headed screw. When the screw is loosened up it will take up slack and put spring pressure on the rod that puts pressure on the cam chain. Now that its taken up the slack tighten down the 10 mm headed stud and then the 12 mmm locknut. That should take out all play in the cam chain tensioner. The cam chain tensioner is located under the carb boots from the engine to the carbs.

Hope that helps and you can understand it.... Darn Vicodin and beer googles... NEVER EVER CRASH ON LAP 2 of an 8 hour endurance race!!!!

Sean

 

Everytime a post comes up on the Auto Tensioner reset, I get confused.

Statemenst seem pretty consistent on the 2 rotations of the motor in its normal direction and then then quickly reversing direction, however when it comes to counter vs. clockwise as normal direction I see posts stating both.

With the side cover off and the bike in gear, I rotated the rear tire in a forward direction. This made the engine rotate counterclockwise, this therefore would be the engines normal direction correct? My jerk back would be in a clockwise direction.

Clarification appreciated.