How much engine and gear noise is normal?

My KZ750 engine is quite 'clunky' at idle. I've recorded a video that shows what it sounds like cold, and at very low revs. It doesn't sound quite this loud in reality, but it gives a good idea.



I would have guessed this would be cam chain noise, but I do have an automatic tensioner - is there any maintenance I should do on the tensioner? If it were valves I would expect it to be much more rhythmic and continue to be heard at higher revs.

What I'm more concerned about though is the gear/transmission noise while at speed. It sounds almost like a rubbing sound, like dirty brakes (it's actually not the brake, but that's the best example I can give). It is only present when in gear and on throttle at low revs. It's also very hard to record, as the wind and engine noise cover it up when recording. I hear it best when riding past a concrete wall or something else that reflects sound back. Are there any common issues with the gearbox that could cause this? In my experience bad bearings or gears are fairly rhythmic too, whereas this is a constant rubbing sound. I'll try to get a decent recording.

Thanks.

Some of that noise is the primary chain. Have you vacuum synced your carbs? That evens out the power pulses at idle and may help reduce the chatter noise.

Regarding the cam chain tensioner, did you check its function while doing the valve adjust? And speaking of valve adjust, if you set the clearances to the wide side of the spec they will make some noise.

My tranny/ primary chain rattles quite a bit at startup and idle and I have seen other 750/4 owners complain of similar. It goes away when rpm rises whereas cam chain noise will not. You seem to demonstrate this in your video. Carb synch will help but wont make it dissapear altogether, at least not on mine.
I just got used to it. 13 years and 40,000 km later I take it as normal. I set the idle at about 11 or 1200 rpm and think that helps.

Sync the carbs. It will make the devil's own noise out of sync. My last chain made clanking and grinding noise but no rub spots I could see. The sprockets looked good and the only way it would quiet down was when it was way loose. New sprockets and O ring chain, it's quiet as a kitten.
Steve

As other members have pointed out, that noise you hear is your primary chain and backlash in your clutch and transmission.
The reason why it is so bad, is that is appears you are running on three cylinders because you have the vacuum line to your fuel petcock unplugged. The carb that vacuum line is plugged into is sucking to much air and is either not allowing proper combustion or is melting your piston and valves.
Address that issue first and foremost.

Irish Yobbo
Daftrusty was faster.
i saw in your video that the vacuum hose at the fuel tap spit back.
This caused a rough idle!
Have you try to block the vacuum hose temporary with a screw?

Daftrusty wrote: As other members have pointed out, that noise you hear is your primary chain and backlash in your clutch and transmission.
The reason why it is so bad, is that is appears you are running on three cylinders because you have the vacuum line to your fuel petcock unplugged. The carb that vacuum line is plugged into is sucking to much air and is either not allowing proper combustion or is melting your piston and valves.
Address that issue first and foremost.

Good spotting. Yes, it the video I did have the vacuum line disconnected which amplified the problem. I had just finished adjusting the choke and needed the tank back on to get it running to test, and didn't hook everything back yet, and took the video at the same time. So yes, it doesn't usually sound this bad, but it's not far off. Besides, I wouldn't get very far without the vacuum line connected anyway

I agree with you all that carb syncing looks like the way to go. I've never done anything with a primary chain before, but going by the manual it looks like there isn't much that can be done except for making sure the carbs are synced and the drive chain is in good order and at the correct tension (which it is).

Nessism wrote: Regarding the cam chain tensioner, did you check its function while doing the valve adjust? And speaking of valve adjust, if you set the clearances to the wide side of the spec they will make some noise.

I haven't actually adjusted the valves yet, I was just replacing a very leaky valve cover gasket. The cam chain looked right according to all the info I could find, but I left the tensioner in place (I didn't move anything so the tension was still set the same).

That may have been a mistake. From what I've read, you are supposed to take out the adjuster wedge before you take the cover off. I'm sure others will elaborate here. Adjust or just check the valves. The 550 I picked up sound'd like that until I synced the carbs then it purred like a kitten. What does your drive chain and sprockets look like?
Steve

SWest wrote: That may have been a mistake. From what I've read, you are supposed to take out the adjuster wedge before you take the cover off. I'm sure others will elaborate here. Adjust or just check the valves. The 550 I picked up sound'd like that until I synced the carbs then it purred like a kitten. What does your drive chain and sprockets look like?
Steve

As far as I know (and I might be wrong) you're supposed to remove the adjuster to prevent it from snapping back in and applying more tension than needed, which is further tensioned when you put the valve cover back on. I just checked for clearance when putting the cover back on, to make sure that it hadn't moved.

I do intend to check the valves some time soon. The only reason I replaced the valve cover gasket without doing so was because it was at my brother's place and I just needed it going quickly (and it was pouring oil through the old gasket).

The drive chain and sprockets are good, no noticeable tight spots and the teeth of the rear sprocket still look pretty good. I'll be changing both sprockets out soon as my sprocket ratios are all wrong.