I noticed  what seemed to be a noise off idle.

 That sound is what I heard off idle when I put the "new to me "1989 K100RS with 88K miles on the clock in storage for a couple of months before I could be riding it much.

I am reading almost all the posts listening intently to all you folks that have amassed so much knowledge about these k Bikes when I read from "Point 75".......

"
The rattle may be a combination of things.

First, the throttle body balance at idle is probably off and causing uneven firing.  You can't really hear it, but it's there."






are we talk'n about the same sound?

wilcom wrote:are we talk'n about the same sound?

These bikes will make a hellacious rattle if they are lugged. They want revs. Use lower gears and give plenty of throttle on takeoff—not wheelie throttle though. That rattle might go away if you do that.

Laitch wrote:

wilcom wrote:are we talk'n about the same sound?

These bikes will make a hellacious rattle if they are lugged.

This sound was just off idle while out of gear. just a soft blip of the throttle and right off idle.

wilcom wrote:This sound was just off idle while out of gear. just a soft blip of the throttle and right off idle it rattled a bit. a rattle that sounded like rod bearings in the old days

Well, let's leave the old days behind. Post an audio file so we can all have a listen. 

Laitch wrote:

wilcom wrote:This sound was just off idle while out of gear. just a soft blip of the throttle and right off idle it rattled a bit. a rattle that sounded like rod bearings in the old days

Well, let's leave the old days behind. Post an audio file so we can all have a listen. 

If you have never tried to buy a 52 Chevy the sound may not be relevant and i don't think it would be picked up in an audio file.

When I bring the bike out of storage this summer I will see what the throttle body adjustment will do for the sound I'm hearing.

Unless your bike has been to hell and back a couple of times with no oil I would doubt that you have a bad rod bearing.  I am on two K bike forums and have read threads for at least the past 4 years and so far I have yet to see a thread or post about a thrown rod.  There was one a while back where someone had bent a rod on a hydrolocked cylinder, and another where an engine swallowed a valve. 

What you are describing is probably alternator knock or slack in the output shaft gear.  Alternator knock is pretty easy to fix, while the output gear slack requires removing the engine and some tear down. 

First thing is to balance the throttle bodies.  That will improve things, and should be done anyway.  Then check the alternator by removing it and starting the engine.  If it's the alternator rubbers, the noise will go away.

Even when everything is nice and tight these engines make a lot of noise.  Like high revs at highway speeds, most of us just get used to them.

wilcom wrote:
If you have never tried to buy a 52 Chevy the sound may not be relevant and i don't think it would be picked up in an audio file.

I owned fastback '49 Chevy coupe with a straight six. It was what I used to haul the string bass, guitars, harmonicas, weed, cheeseburgers, jugs and personnel of the band from gig to gig in the late '60s.

My philosophy today is if it can't by heard on an audio file it, it won't bother me.

On the '56 V8 my friend had, you just removed the spark plug in the cylinder that knocked.  When you got down to 4 cylinders you emptied the car except for a screwdriver to remove the license plate when you couldn't do 30mph anymore.