Vibration at 5000 rpm on 650 Maxim

Just took this latest bike I've been working on ('81 XJ650H) out for its first good test ride. Seems to be running quite well, but there's a vibration at right about 5000 rpm. It's a buzz I can feel through the whole bike and it happens both accelerating past 5k and decelerating back down through it. Is this something that's characteristic of this bike or might I have a problem with the drive shaft?

Thanks.

 

Do a search of the forum. I have exactly the same problem with my '82 XJ650J and asked about it on here. I've been trying to track down the 'buzz' for over a year and think I have it narrowed to one of the header pipes. There's little rubber dampeners between the fins on the front of the engine you can check. All of exhaust pipe connections. Seems around 5000rpm these bikes harmonically align with the universe and all hell breaks loose.

 

Yep, it's well documented. I have the same bike, and the buzz is there between 4900 and 5000. It seems like it became less harsh after I checked my valves and got them into spec. So, if everything is tight, and your valves are in spec, and your bike is running right, it should not be too bad.

 

Well, I just adjusted my valves. Not sure what to think about the exhaust header theory.

Is this something experienced by everyone who owns this bike or just a few? Was it present when they were new?

 

That buzz is just your bike gently reminding you that it's not perfectly tuned and/or clamped down.

Mine was pretty bad, but when I put on new exhausts it went away completely, so much so that I took the vibration dampeners off my wishlist!

Not that yours is the exhaust...but it is something.

 

Yep my xj650 aligns with the harmonic universe (maximum buzz) right at 4,750 RPM's up to 5,100 RPM's. At 5,200 RPM's all is smooth again. It is annoying because that RPM range is kind of sweet spot for me. I installed a set of Vibranators which helped a little (reduced vibration I would say by about 33%). I wanted to try the Vibranators because they are completely concealed in the handle bars (keep a stock look). Many people recommend Bar Snake but it's pretty permanent (i.e. fill up your bars with a liquid and let it harden). I'm planning on trying new motor to frame bushings, valve adjustment, vacuum synch, and color tune will help (when I get to it this fall)

 

This is all very interesting. I just came from the local Yamaha dealership where I bought a new front tire, and the service manager was telling me that he put 30k+ miles on one of these and had the same issue. He said his got better when he got close to 20K miles.

 

They all "buzz" at that rev range.

HOW MUCH is dependent on a whole litany of things; the more of them you address, the smoother the bike will be.

Motor mount isolators are often overlooked because they're hard to change; although some of the bikes have solidly-mounted motors.

State of Tune makes the biggest difference, though, beyond a doubt.

 

Interesting. Well, I'll keep tweaking it and will check out my motor mounts, too. Thanks.

 

I have over 21K on my bike now the last 5K all mine and in the last 93 days. My bike buzzes in that RPM range too, though I've just gotten used to it and I don't really notice it much any more.