Buzzing/rattling?

So I noticed my bike has a pretty gnarly buzz at 5000 rpm. It's pretty loud, and it seems to shake up the the bike a good bit. It really just happens at 5000 Rpm. If I let off, or roll on the throttle, it goes away.

Is this normal?

 

The XJ series has a natural "buzz range" (on most bikes) just below 5Krpm that goes away just above 5Krpm.

This can be GREATLY minimized, to the point of being almost unnoticeable, by getting the bike in a solid state of tune. Valves in spec, carbs cleaned and properly sync'ed, etc., you can make it almost go away. Almost.

If the bike is out of tune, the more out of tune-- the worse it is. Plus it will be magnified by any loose component anywhere.

 

Cool. That's exactly where the buzzing happens. I still have yet to do a vac sync, and my mixtures are all over the place. My loose headlight and keys probably add to it as well.

 

Yep. Plus exhaust heat shields, loose or too close to the frame; cables; a metal relay or two with a broken rubber hanger; something too close to the inside tunnel of the tank; loose bolts anywhere--- you name it.

Vac sync makes all the difference; do it right (since you've got the valves in spec) and you can make it almost vanish.

But you still gotta fix all the rattly stuff.

 

Ha, now that I think of it, I've got all kinds of dangly things under the tank that still need to be tied down.

Seems like most of my problems can be solved by doing a sync though. I'm still getting some stumbling and weirdness at low range too. Hopefully I can get some time this week.

 

Make sure the float levels are spot-on.

Be sure the bike is fully warmed up beforehand. Use a common box-fan (window fan) to provide air cooling during the process.

Block YICS properly; if you don't have a tool, use the oiled-rag rope method.

BE patient and don't over-adjust. If you got a decent bench sync and the float levels are good, it won't take much adjusting.

"Blip" between tweaks, and wait for the motor to settle down.

If it begins racing, and won't settle down or behave, it may be getting hot; shut it off and go take a 7~10 minute break. Not too long, or it will cool down too far.

It's worth the effort. I like to ride my '83 right IN the "buzz range" just because it doesn't do it any more.

 

Cool. Thanks for the tips.

 

Awesome info here, never knew there was a solution!