"knockin", but fades with RPMs. Chain / Primary noise? XJ550

It's always a joy running a bike after adjusting the valves, a running sync, and some RTV'd intakes... however I've got a "bottom end" noise.

On the center or side stand and on the ground there is a distinct slap in the bottom end, left side. Seems like the primary cover based on my stethoscope.

If I remember right on the 550's the chain is driven right from the primary (or I could be mixing up bikes)... any chances I can be lucky and it's just slack?

The chain deflection on the center stand is ~1.5"
The noise fades with RPMs, or even if I bump the idle from 1200 to 2000.

 

You're lucky.

The 550 uses its primary chain to actually drive the bike, and it is hydraulically tensioned using engine oil pressure. This is why the sound goes away as soon as you rev it.

A certain amount of primary "slap" at idle is normal. The effect can be greatly minimized by getting the carbs balanced and taking the "lope" out of the idle.

All 550s do that, some moreso than others.

 

I just did some searching myself about the ticking/whining noises. My bike sounded pretty noisy today on my little ride when just off idle. Different design from what I understand, but still a bit unnerving.
Based on the searching, I'm gonna try the cam chain tensioner adjustment/reminder technique, and double check the valve clearances. Also, gonna check for an exhaust leak.
Other than the sound and a little burble just off idle the bike runs excellent. Took her up to 8k rpms and it pulls hard all the way up. The burble is more pronounced cold, after warming up it's almost gone.
Once I have the above stuff done I'm gonna synch one more time.

 

Do the 650s make this sound as well at idle?

 

if your running regulatr automotive oil. bikes don't like it. they prefer genuine synthetic motor. all of the bikes i have owned also shifted harder with regular motor oil.

i had a ninja 600 that knocked at idle. didn't do it after an oil change.

i've seen bikes do some strange things if the oil wasn't motorcycle synthetic. i hate how bikes are expensive but what you gonna do.

3 quarts of oil at $4 a peace for a knock in the motor. $60 a gallon for motorcycle oil and no knock.

 

Not really. The sound the original post refers to is unique to the 400/500/550/600 motors that use their primary chain as a true primary, to drive the gearbox.

The 650 and bigger (shaft driven) bikes have geared primary drive, their "primary" chain only serves the starter and alternator.

The chain-driven bikes don't have the "middle gear whine" characteristic of the big bikes.

 

Thanks for affirming Fitz!

 

No sweat. It worried me too, until I got a factory book AND the Cycle magazine road test (from Feb. '81) and actually SAW what was going on. Once you know what you're looking for, you can find it in the "crankcase" diagram in the fiche.

Get your 550 idling like a sewing machine and it will nearly go away.