81 XJ650 Timing Chain Question

So the other day I was sitting behind a truck at a stop light and my timing chain started to rattle. The bike idles and rides fine but at soon as that started I rode about another 1/4 mile to my destination and haven't ridden it since because I didn't want to risk the chain breaking and causing some real issues.

I know the only two things it could really be is either the chain tensioner or guide. My question is when setting the tension on the chain with the auto tensioner pinch bolt style (the factory tensioner), where do you set the motor so the chains at the most slack point? Wheres the mark? Or is it set when idling? I don't have a manual so I cant figure it out. Thanks in advance for any help.

 

you should have mentioned what bike you have so we can more accurately answer your question. but if I read your text right. you think that your tensioner is automatic, but you mention the pinch bolt. if you have a pinch bolt, then your tensioner is not automatic. do not loosen the pinch bolt with the engine running!

here is the proper procedure for a xj550...


timing chain adj by bmonkey36, on Flickr

CN

 

If you're riding a 1981 XJ you had better get a manual and soon.

Ignorance is NOT bliss when it comes to these motors.

 

@cyclenoob Its a 1981 XJ650, not a maxim either. And yes that was my mistake, its not an auto tensioner. I work on cars professionally and have just recently started to dabble in bikes and its a whole other animal. Is the procedure for the XJ550 the same as the 650?

@bigfitz52 Thats what I figured as well once I poked around a bit, this things real foreign compared with newer bikes Ive worked on. Just trying to avoid spending the $50 on a manual just to know where the timing chain tension mark is.

 

I would expect that the procedure should be the same. that is, provided you do actually have the manual adjuster. does it have the stop bolt and lock nut on the side of the adjuster? or just a bolt in the end?

CN

 

There's not really a slack point. Basically, take the side cover off, loosen the tensioner bolts, rotate the engine counterclockwise to tdc, then retighten the bolts(if it's a "manual" tensioner).

 

Its a stop bolt and lock nut on the side.

UPDATE: So I took the cover off and there was the mark, missed it when I took it off last time cause it was caked with dust. I rotated the motor counterclockwise to the point where the C and stationary line were lined up. I loosed the locknut and bolt and didnt hear anything like the slack being taken up but I tightened it up anyway and installed the cover. Still rattling sadly, pretty much no difference.

Ive removed the tensioner and the spring feels fine and whatnot and the lockbolt holds the tension when I physically push on it. Is there a way to tell if its bad? Or do you just replace it?

I want to try that first because the only other thing it could really be are the guides and I know those are a bear to get to in order to check and even worse to replace.

 

You might want to try rotating the engine counterclockwise once with the tensioner loose. If that doesn't work, something's wrong.

 

before you loosen the tensioner lock bolt back up. try rotating the engine clockwise for about a quarter turn. you will have to have the valve cover off for this. once rotated clockwise, try lifting the cam chain in the middle of the flat spot. my wifes 550 had slop when rotated backwards before I made the adjustment. now there is no slack when rotated backwards. while you have the cover off. try having a look at the guides.

CN

 

Alright Ill have to give both of those ideas a shot tomorrow. Ill let ya guys know the results as soon as I do. Thanks for the help everyone.

 

Whoa. If the cam chain is truly rattling that bad, a guide may be out of place or broken.

The CAM chain guides aren't a bear to replace; the "primary" chain (jackshaft chain) guide is the one that requires splitting the cases.

TAKE THE VALVE COVER off, get a flashlight and an inspection mirror and figure out what's going on before something bad does happen.

 

If you're planning on keeping that bike for any amount of time, you really should get a manual. It has all sorts of important information that you'll need like torque specs, wiring diagrams, etc.
Sure, this forum is a great source of information, but you still should have a manual. It's the most important "tool" in my toolbox

 

Seems to be a recurring theme in our responses...

If you're careful you should be able to find a FSM on eBay for around $25. The Haynes retails for around that.

There are a LOT of "non-intuitive" intricacies to these bikes; you're going to need a manual to keep from screwing something up.

 

Thanks for the replies everyone. I do enjoy this bike and do intend to keep it a while as long as it isn't something real major cause manual or not I am not splitting the case halves. Did that once on a similar bike and its not for me. But I do intend on getting a manual, this bike is just a very recent purchase so its disheartening when something goes wrong with something new (to me).

And yes at this point ill pull the valve covers and take a look I was just procrastinating the inevitable.

 

So i pulled the valve cover off. The chain tension looked good but I found this:






Id assume this is the easy guide to replace? The cam sprocket and teeth look good even though it ate up the guide. It'd be nice if this is all it is.

 

Whoa, I would have to wonder how the guide was relocated into the cam sprocket in the first place like bigfitz mentioned it may have done. This is interesting now that I see pictures; before I was just letting the gurus speak & listening into the conversation. I had a similar problem (much more serious-and it was MY fault) happen to my 650 which has been sitting in the shed for quite some time because I don't want to get rid of it but yet struggle to find time to fix it. If you recently purchased the bike & you've been stuck with this kind of problem now, you may have a lot of learning to do! Also this goes to show you cannot trust anything the previous owner did or told you (s)he did. As previously mentioned, without a manual you'll be taking bolts off and looking at an engine in the dark.

 

We need some better focused, smaller pics.

But if it is what I think it looks like, then yes. That guide is easy to replace. It looks as though it shifted position for some reason; it's supposed to be more or less centered on the head, front-to-back.

 

Ding! Ding! Ding! We have a winner!!
Good call Fitz!

Not sure if Chacal has them for sale or not. Send him a PM or email him at info AT xj4ever DOT com. If not there's a slew of them on fleabay.
While you have the valve cover off you should check your valve clearances. Especially if you don't know when it was done last. Here is a link to a great write up by Fitz.
You'll probably need to replace the valve cover gasket and the "donuts" on the hold down bolts before you button it back up to avoid oil leaks. Those donuts are what provide the pressure to hold the valve cover tight against the head.

 

It's an '81. The valve cover does not have donuts like the '82-'83 models. But yeah the valve gasket itself (paper-not rubber like the '82-'83 models have) was probably destroyed during removal if I had to guess.

 

Ah thanks moellear, I wasn't aware of that difference between years. I knew the valve cover appears different but thought it still had donuts to hold it down.

Learn something new every day...which is why I love this forum!

 

IF it's a truly an '81, with a pre-YICS motor, then that is indeed the case.

If it's an '82 bike made in '81, then it could have a YICS motor (and "donuts.")

tbalonick, please put your bike info in your sig. If there is any uncertainty on your part as to what you have, look here: http://xjbikes.com/Forums/viewtopic/t=14577.html

 

Yeah sorry about the pic size and focus, I uploded them to my website from my phone so I couldn't crop them. But yes it looks like the rubber part that the chain rides on got eaten up or fell off and the guide just worked its way into the cam sprocket.

I'd assume the guide is just held in by chain tension? And yes this is a true '81 motor, just a paper gasket and its fine, no rips, looks like it was replaced recently cause the valve cover just slid right off, no sticking at all.

I just ordered a new guide off ebay so will see how that goes. Ill post the results here when it comes in. And yeah ill probably check clearances while I'm in here. Thanks for the advice everyone.

 

Cool. Now please put your bike info into your signature so we don't give you contradictory or wonky advice.

 

Well good news and bad news. Got the guide installed and the chain properly adjusted and NO MORE RATTLE! However now that the bikes running again the engine has, and I don't know if this is the right word, a slightly more muffled sound. And when reved sometimes it drops rpm like its going to die instead of going like it should. So all in all I'm pretty sure it jumped a tooth or so with timing would be my guess, on to the next fix :/

 

One tooth would be a mile out.

 

However the failure happened up top, something wasn't right to begin with and you were used to how the bike ran that way. Then it "let go" altogether, but something was amiss for a while before that happened.

Step one: Procure service manual.

Step two: Re-check cam chain tensioner adjustment.

Step three: Take the valve cover back off and check the cam timing. It's only a matter of turning the motor to the right position and checking the alignment of the dots and arrows. A SERVICE MANUAL WILL SHOW THIS NICELY. Depending on which manual you have, one of us can tell you what page to look on even.

Step four: check and adjust valve clearances if you didn't already.

Step five: run a compression test to ensure a valve didn't get bent in the loose chain/tensioner destruction debacle. But get the valves in spec first as not to panic thyself.

So, back to step one...

 

The bike may not be listed in the signature, but it sure is listed in the forum heading...........for those that hadn't seen it-------

Dave F

 

We're is this cover to the adjuster located on my 550

 

You will find the cam chain adjuster below the carbs (there is no cover for the adjuster, but the valve cover also covers the cam and cam chain). There is a procedure for adjustment. A search should turn that procedure up for you.