Identify my new engine rattle - 1981 KZ750 LTD

Started up my bike to go in to work today, and I made it about 50 metres down the road when the engine starting making a new rattling sound. The sound is coming from the left side of the engine. The noise is related to the engine speed and happens if it's in gear or not, or if it's in neutral or not. Since the clutch is on the opposite side I don't think it's that, unless, it's just a part that's come loose and rattling in the cover, but it sounds too loud for that. There's a video here:



Any ideas? It wasn't revving high or under load when it started, I was just rolling down the hill at about 40kph.

You seem to have forgotten the link.

Just guessing but I'd say starter clutch issue or the rotor may have come loose.

I had used the 'video' link instead of the 'provider' link. Try that.

Sounds like it's coming from the alternator cover. Use a long screw driver against your ear to pinpoint it.
Steve

I have a mechanics stethoscope (which is really a small doctor's stethoscope I got as a child, which I've modified into a mechanics one) and I'll check that when I get back home. It just happened this morning, so I went back home, took the short video, then caught the bus in to work. I thought I'd just gather intelligence so I know what to look for before getting back.

I'm in Australia, if you're confused about the time

Check the cam chain adjuster area as well.
Steve

Can chain and adjuster is on my list to check, however it doesn't sound so much like chain noise. I think Nessism and SWest might be on the mark with a loose rotor, I could see that making this noise. But having never dug into this engine at all I don't even know where the rotor is - I presume the left crank cover? If so, that's where the sound appears to be coming from.

No eBay APP ID and/or Cert ID defined in Kunena configurationThat's the alternator cover. Might as well order the rotor removal tool.
Steve

Got my studio cans on, I hear some clutch basket and bottom end /primary chain clanking, increasing the idle and balancing carbs will minimise but not eliminate this. Was this a cold or hot motor?

Camchain rattle has a distinctive 'bunch of keys' tinkle to it and most pronounced at about 3k when the throttle is blipped. Not the sound I'm hearing.

Alternator rotor come loose / fastener(s) gone awol /or magnets delaminated? Use impact driver and threadlock here.

Try putting a rag over the exhaust temporarily and you can hear the motor a lot more clearly.

Any smoking / loss of power or charging issues?

I've had a bit of primary chain noise since I've had it. This is a cold motor and yes, it disappears with revs (which is why I sped it up a little later in the vid). Carbs are synced, but I suspect one or two might run a little richer than others. But nothing I'm too worried about right now.

I didn't notice any smoking or loss of power, but I was literally 50 metres down the road when it happened (which is why it's cold), so I haven't ridden it enough to notice. I just rode it back and parked it.

I've read a few threads on rotors mentioning to use an impact driver and threadlock. Normally that sounds like a big no-no to me - is this because there is no easy way to lock the crank for tightening? Any chance I'll be stripping bolts if I do this?

I have it in gear and use the rear brake when I'm tightening large bolts or nuts.
Steve

SWest wrote: I have it in gear and use the rear brake when I'm tightening large bolts or nuts.
Steve

I did the same for the crank nut when changing sprockets without issue - can't see any reason why I couldn't do this unless there is a component that can't handle it? I would have thought dropping the clutch would apply more torque than I could.