HUGE 'Clunk' when shifting from neutral into first gear.

My 1983 Yamaha XJ900R is a really lovely bike. It has less than 10K miles on the ticker and looks near-new, such was the care it received before I acquired it. It does have, however, a couple of unsettling little traits that give me some concern. One is an irregular, slight 'ticking' noise that sounds as if there's a small metal bit being knocked around in the sump. This noise is most conspicuous on a cold start (engine not warmed up), but doesn't seem to have any effect on operation of the machine. It becomes a bit less apparent after the engine has warmed up, oddly enough, and doesn't seem to present itself in the other gear shifts (2nd, 3rd, 4th, etc.). The second bothersome trait is a large and solid 'CLUNK' after I have let the engine warm up and shift from neutral into first gear. The 'THUNK' occasionally stops the engine from turning over and I have to restart it. After that first big THUNK, it doesn't seem to reoccur for the duration of the engine's operation. The possibility that these two noises could somehow be related is unsettling, but I have no clue as to what may be causing them. Any insights from wiser, more experienced XJ900R veteran-users would be most appreciated.

 

check the adjustment of the clutch.
my 750 clunk on the first shift into gear after starting for the first start of the day, also tends to lurch a little .but that is likely due to how a wet clutch works.
the oil has a connection to the clutch plates and until fully warm and thinned wants to turn the transmission even with clutch pulled in.

you can see this action with bike on centerstand in neutral rear wheel still spins

what oil do you run?

the "primary"chain in the motor is tensioned by an oil jet this could be the sound
oil pump is also driven by a chain.

when was the last time you checked valve shim clearance? shims make a tappy ticking sound when properly adjusted

 

Thanks for the return on my query. I use regular 10w50 Castrol in the XJ900R. I thought of checking the clutch adjustment and did adjust it somewhat: no luck. Something else I tried was starting the bike and letting it warm up somewhat in neutral initially, then switching off and with ignition still off putting it into 1st gear and 'rocking' the machine slightly (as if attempting a push-start), then switching ignition on again with the machine back in neutral. This 'cures' the problem occasionally, but is puzzling to me. Haven't a clue what that might signify to a far more experienced XJ person. Any ideas there? I usually use the side stand, but I'll put the bike on its center stand as you suggest & see what it does. The valves are properly adjusted, BTW (they do make the tappy ticking sound you describe). [The 'CA-THUNK' I cited is a real 'grabber'. It usually stops the engine cold.]

 

PS: The valve 'tappy ticking sound' well adjusted values make has a regular rhythm, whereas the strange little 'ticking' sound I described originally is an irregular, sporadic rhythm (exactly as if a small loose metal bit is being swished around the sump and hitting the side of the sump casing).

 

Just a follow-up for anyone who was perhaps following this. The irregular 'clickety-click' clicking noise I previously mentioned that was so perplexing AND the 'Ka-Thunk' sound the gearbox made when I shifted from neutral into first gear (from a standing start) has been dealt-with by following the following protocol: Before starting the bike in neutral, I shift it into 2nd and (with ignition off) and push it along a couple of feet (as if I were trying to push-start the bike), releasing and gripping the clutch lever once or twice. That routine seems to take care both of the random clickety-click noise and the kathunk, since thereafter upon putting it back into neutral and starting it, both noises are noticeably gone. This suggests to me that the clutch engagement mechanism is somehow sticking, since the slight ignition-off 'push' in gear releases whatever sticking was ostensibly causing both sounds. I suppose this means that ultimately I will need to open up the case and check to see what the clutch sticking is actually being caused by (and replace whatever component is at fault). But meanwhile, as long as I do this 'pre-start' routine before start-up, the bike seems to be otherwise operating fine. A motorcycle mechanic would probably hear all this and immediately guess the source of the anomaly, but until I get it to a shop where they can diagnose and repair such strange quirks, I seem to be OK to ride following this 'make-do' approach. In all my years of operating bikes, this is the first time I've ever encountered something as weird as this. Odd! Since the bike is otherwise virginal (only 8000 miles on the odo), it's doubly odd. Ah well! Live and learn, as Robert Persig undoubtedly said at one time or another. [Images of 'Scarlett', my '83 XJ900R Seca, below; the other bike is 'Fugu', my 2000 Kawa ZX900E-1 Ninja, for anyone curious.]

 

my guess would be , " if the bike has been stood for quite a while" with the clutch ,half in and half out of the sump oil, then a "goo" develops on the exposed half of the clutch plate , mainly the solid steel ones, i think the plates might need cleaning with a Scotchbright pad.
it'll cost you nowt to clean them up , except a clutch case gasket
stu

 

My XJ doesn't do it, but the GSs are chronic for cold clutch grab. It gets worse with lower temps and thicker oil.
I developed a technique of starting it on the centre stand, letting it warm up for a couple of minutes, then pull in the clutch a couple of times to help it free off. I then switched off, still on the centre stand, put it into first gear and started it, while pulling the clutch in and pressing on the rear brake pedal.
That would free it off nicely.
Since I rebuilt the top end of that engine and fitted new clutch plates it's been no trouble. Prior to that I'd used lighter weight oils and while they definitely helped a lot, they weren't as good as a new clutch. The old clutch lasted well though, it must have had 100k on it. Plenty of life left in it too, but with its tendency to grab, I'll probably never use it again.
These days I'm using a 5w50 oil, and normally I use a 5w40. Anything heavier, like a 10w or 15w would be inviting trouble in the winter.