Engine vibration, or "buzz"

[newmaac]

I have been reading Dragon Tamer's thread on vibrations.

I have what feels like a low end engine vibration at about 6200 RPM. It is very pronounced and mostly felt in the pegs. I have mentioned it to a couple old Yamaha owners and was told, "that's just a buzz, push through it and it will go away"

Since I have ridden for so long at lower RPMs, staying below "the buzz", now when I do push past it, I am not used to hearing the high revs and I feel like I am abuzing the poor thing.

I occationally ride with a buddy from the XJ group. He laughs and tells me that I am missing out on all the fun, by basically staying below the power band.

Is it common to have this type of vibration?
I just rebuilt the top end. Having increased the compression, I have more power, but the buzz is still the same.

???

[rockjok]

I had a similar problem with my low miles MNS. At "low" highway speeds no problem but there was a zone around 65 that sounded and felt like something was ready to come apart.

I finally traced it to the heat shields on the exhaust pipes below the footpegs. Perhaps this is another reason the stock pipes commonly crack out in this area.

On another bike with Jardine 4 to 2 pipes the kickstand would occasionally rattle against the pipes. Solved this with a rubber test tube stopper with a hole drilled in it stuck over the kickstand stem.

Rob

[newmaac]

Thanks for the input Rob, but this is not really a "sound thing". It is more of a feel thing.
It feels like something is way out of balance, but it only comes-in at 6200. When I DO go past that range it is usually for very short periods of time before a shift, so I can not really tell if it smooths-out at any point.
I am headed of to work right now, I will try to get a better description while on the freeway.

[MAXIMAN]

I don't feel it. I just totally rebuilt Zilla and at 6200 RPM he is smooth as glass and singing like a little bird.

Have you checked your motor mounts?

[HobbyMan]

I know the glass feeling!

[Dragon Tamer]

Sounds like just what I am working with but mine is at a lower rpm, at the rpm's you are talking about mine is "glass smooth", still another piece of the puzzle!

[newmaac]

Well, after playing around a little, I found that the buzz does go away when I push past it.
At about 6800 it smooths out. At 7500 it COMES TO LIFE. The brief moment between 7500 and 8500 is pretty awsome. I wish that it had a power band like that a little sooner, so that it was more usable.
I mentioned to my son how quickly it shot from 7500 to 8500, and I said something like "what's the point in that?".
His quick response was "Well, then you hit the next gear and do it again!" )

Ahhh, youth!

I only have about 150 miles on a new set of rings. I guess that I should go through a few tanks of gas before I get too carried away.

[firecrackerboom]

i read somewhere that youre supposed to really rapp it up rigt when you put in the new rings so they can seat properly or whatever. donno if thats really true or not...

[Crazcnuk]

A friend just bought a 79 Special, about amonth ago. He has the same problem.

He asked me to take it for a spin to see if I noticed anything, not telling me what his worry was.

I got back after about 1/2hr of twistie road cruising. He asked if I noticed the vibration at around 6K.

I looked at him and said I didn't notice, but I spent about a millesecond going past 6k!

His is the same, above 6500 it's like silk (pfft glass!) below it's fine. just has a spot in there where it vibrates a bit

I just never spend any time in that range, I am either cruising at limit or I blow through to 8000ish