Good vibrations?

[LynnLegend]

Hello,

This is a bit of a vague question, but how much should my A7 be vibrating?

I have read a few posts where members have said that there is "excessive vibration" or "lots of", but having had no real experience of classic bikes I'm unsure how much is too much.

The bike is fine up to about 50mph, above which there is enough vibration to make my hands and idiot itch. It's not too bad, I just have to loosen my grip a little bit and shift around on the seat. The handlebars have next to no twistgrip and the seat has seen better days.

If she should be whisper quiet and silky smooth, then something is amiss. If some robust vibration is to be expected then I'm happy it's normal.

Please don't suggest that I "simply get the engine on the bench and inspect the bottom end" - I don't know what I'm doing and don't have a workshop :-)

Sam.

[Black Sheep]

My A7 is pretty smooth. It sit happily at 65 mph (give or take) and you can ride it all day without white finger syndrome. It does vibrate - they all do Sir, but not that much.
First port of call is the head steady. If that's loose, vibration will be severe. When my Norton had a loose head steady, it vibrated the plates off the battery somewhat inconveniently 100 miles from home.

[LynnLegend]

My A7 is pretty smooth. It sit happily at 65 mph (give or take) and you can ride it all day without white finger syndrome. It does vibrate - they all do Sir, but not that much.
First port of call is the head steady. If that's loose, vibration will be severe. When my Norton had a loose head steady, it vibrated the plates off the battery somewhat inconveniently 100 miles from home.

One thought which crossed my mind is that between 50-55mph in 4th might just be a bad 'range' - I've never taken the bike above 55 so it may well smooth out beyond that.

Losing battery plates is inconvenient, how selfish of your bike to do that!

[jachenbach]

Let me start by saying my A10 is not yet in running condition. I have, however, owned a number of unit construction Triumphs and BSAs and a few Norton Commandos. All except the Commando vibrated quite noticeably (Commando smooths out around 2k rpm). If you have been riding modern counterbalanced bikes, then I expect you'll notice the vibration quite a bit. Heck, some folks complain about Moto Guzzi and BMW twin vibration. Guess they haven't traveled on an ironhead Sportster! I realize this answer is probably not much help, but really, what degree of vibration is objectionable/normal is rather subjective. I'm not aware of any sort of vibration meter with which it can be quantified.

[muskrat]

G'day LL.
My A7 is a lot less viby than my A10. My A7 develops a harmonic buzz at about 60mph so it's either above or below this (mostly above) that I cruise on.
Most bikes have a sweet spot. My rHonda is about 75+mph. Not good for the retention of the license but fun.
Cheers

[edboy]

hi muskrat,
if you over advance the ignition slightly [so the bikes hunting] and have a nice carb mixture, then why can you rev an a10 from 40 upto 80+ mph with virtually nil vibration.i found this out by chance the other day . i doubt the bottom end would last as long ticking over at around 50mph  but if i was racing i would try it out. i also wonder if this is how bsa road tests achieved 110mph.

[muskrat]

G'day Ed.
Depends on the grade of the fuel and the comp ratio. Hi octane fuel needs more advance, high comp needs less. The you factor in the balance factor. Oversize pistons, non genuine make, alters this.
You may have found your bikes sweet spot.
Cheers

[edboy]

hi muskrat, i believe your right and i will adjust carb to run leaner on lower settings. retarded ignition maybe the cause of vibrations at 50mph?