1986 XJ700X cam chain slack?? - very noisy

This very morning when I started my bike, I heard a rattling metal-like sound coming from the engine block. Immediately shut down my bike, took a few seconds of thinking, started it up again, same noise again, but no other audible or noticeable problems. Took it for a short trip around the block and no problems either, except the added noise.

Now, I'm thinking it's the cam chain that 's got too much slack, but I'm looking for more confirmation/other ideas and ways to confirm this thought.

Bike is a 1986 XJ700X, with 42000miles, got it at 39000miles, been riding the last 3000 miles without any problems. I did do a valve clearance check and fixed all clearances when I got the bike. Also replaced the oil (there was hardly any oil in it.)

Noise follows RPM increase and decrease, but at higher rpm (4k+) it seems to fade away. It's most audible when idle, but it's not constant. Kind of comes in unregular short waves.

Did some research on this site and decided to ride the bike to work and did so without any problems.

But, when I get back home today, I'm going to check the tensioner and remove the valve cover so I can check chain slack.
Not sure how much slack is too much slack. Maybe someone here can tell me?
In case it is indeed the cam chain, can it be replaced without an engine split?

If it's not cam chain slack, what else could it be?

Thanks in advance, hoping to fix this issue, as I really like this bike.

 

keep us posted, i have the same problem. valve clearances are good. only thing i can think of is it must be the chain.

 

Took apart the tensioner today and removed the valve cover so I could have a look at the cam chain. Both tensioner and chain seem to be OK. As far as I can tell, there's not a significant increase in slack last time I checked (3000 miles earlier). Even doubt whether there is a difference. Put it all back together, fired it up, noise still there. Still runs fine, starts right up, shifts up/down also OK and rattling/noise faded away from 3k rpm and up. Most audible when idle.

I'm starting to think it's something different, but not having a clue what it could be. Talked to dealer about cam chain replacement, can be done without splitting the engine, but I'm not sure that'll fix my problem.

Going to keep the bike grounded at least for a couple of days. Don't want any irrepairable damage, even though there might be something quite damaged already.

If anyone has an idea or some insight that might help me, I'd be very thankful.

To be continued...

 

I made a recording of my bike while running. Maybe an experienced listener or mechanic can make something out of this.

https://www.youtube.com/watch?v=XD8by3EDXqU

 

If the Bike has more than 50,000 miles, ... replace the Chain.

If not, ...
Do a manual Tensioner RESET.

Pull the Plugs.
Pull the Left-side Crank Cover.
Using the Flats on the Timing Rotor ...
Crank the Engine over 2X in its NORMAL Rotation.
Then, QUICKLY Crank the Engine over in REVERSE Direction.
(This presents the Slack before the Chain Tensioner. It helps to have an assistant tapping smartly on the Bolt-head at the end of the Tensioner)

The Tensioner should Ratchet Out to take-up Slack.

Repeat process 2~3 Times until the Slack's all out.

 

Bike's got 42000 miles on it.
Tried a manual reset today, but tensioner seemed find.
I'll try it again the way you described it, because I just re-assembled the tensioner and cranked the engine over (no backward stuff).

I thought reverse-cranking the engine is bad?

Thanks! I'll let you know if it worked.

 

I am by no way an expert, but that sounds like a connecting rod bearing has failed and you are hearing a rod knock against the crankshaft. Just a guess, I will let the experts chime in...but I wouldn't run the bike until it was isolated and repaired...

 

Exhaust leak maybe?

 

Sure sounds like it could be an exhaust leak.

That is NOT cam chain noise. Either it's an exhaust leak (at the head) or something bad has happened at the head-piston-rod level. It doesn't sound like bottom end or rod big end; it's up top. It could be a piston pin/circlip, con rod small end, broken ring...

or an exhaust leak. Which will sound like all sort of mechanical disaster has happened.

STOP MAKING IT DO IT. Investigate. LIMIT running to subsequent diagnostic efforts and quit revving it up! But start by dropping the exhaust at the head and inspecting (for signs of burn) then replacing (because you should) the gaskets.

 

Thanks all for the advice. Looks like I'm going to have to do some more digging.
Will go first the exhaust leak first.

To be continued and I'll keep you posted