How smooth should an A7SS be?

[Tukig]

I was wondering how smooth (or rough) should an A7SS be at 60mph or above. Mine seems to vibrate more than my rose tinted memory remembers my 750 Bonnie or even my old B40 ever did. Is my mind playing tricks or is something much more sinister going on? The recent post on vibration prompted this query and I would be interested, and probably eventually worried, to hear other riders experiences. Ta very much.

[MG]

Hmm, my A7 is much smoother than the A10, especially at high revs. But it IS vibrating obviously. You got two pistons, big ends and conrods oscillating, as opposed to only one in a single like the B40, so I wouldn't be surprised if it was vibrating more. But more than a 750 Bonnie with it's bigger pistons and high compression? I would indeed be worried about that!

Cheers, Markus

[Tukig]

Thanks Markus, The bike is actually quite unpleasant above 60. So I knew I was correct - If in doubt.....worry. I'll probably wait until I have time and money for a look at the engine or until something goes bang, whichever is the sooner!

[muskrat]

G'day Tukig,
                I agree with Marcus. My '57SS before I molested it for racing was quite smooth at 60 +, almost as good as my '51. Now that it's the A10 cafe (10.5:1) and everything is balanced (even the rockers), it's only about 10% worse but not as bad as my XT500.
Cheers

[wilko]

Tight and dry primary chains cause horrible vibration?

[BSA_54A10]

As can out of balance clutch drums, out of balance wheels. bad timing , particularly if the points cam ring is out ( and a lot are ).
Then there is piston weight , it goes on and on and on.

Every engine will have a spot where most of the vibrations cancel themselves out. we call it a "sweet spot" it can and dose vary from bike to bike so the go is to find the rev range where you have the least vibrations and then adjust the gearing so that you are riding in your sweet spot most of the time.

[muskrat]

Your right again Trevor. The '51's is 50-60, the cafe is 90-100 so to keep my licence I stay in THIRD  LOL
Cheers

[Tukig]

Thank you all, I will start with having a look at the cheapest option first (mag cam ring). It starts really well though and is smooth up to about 50 but obviously worth a look as I presume the effects of any wear will be worse at higher revs. On the subject of revs... the bike does feel though its reving quite high for the indicated speed. whats the highest gearing I could practically fit. At present there is an 18 tooth engine sprocket and a 19 on the gearbox. I think this is standard. Just had another thought, perhaps my speedo is out and I am actually doing 90 mph which is why my fillings are falling out!

[Mosin]

Hi Tukig,

It seems to me that discussing amount of vibration on't internet is subjective to the point of not really being helpful at all. What may be of far more use to you it to get your leg over a few other A7 Shooting Stars and compare for yourself. Where abouts in the world are you? If you happen to be anywhere near North West England you are more than welcome to take my 1960 A7SS for a spin to give you a reference point. I am sure that other forum members would be equally happy to offer the same with their machines depending on your location.

Good luck,

Simon

[A10Boy]

I agree with all the above, but is it a rumbling vibration thru the pegs or a harsh white finger inducing vibration through the bars / seat?

[Triton Thrasher]

Thank you all, I will start with having a look at the cheapest option first (mag cam ring). It starts really well though and is smooth up to about 50 but obviously worth a look as I presume the effects of any wear will be worse at higher revs. On the subject of revs... the bike does feel though its reving quite high for the indicated speed. whats the highest gearing I could practically fit. At present there is an 18 tooth engine sprocket and a 19 on the gearbox. I think this is standard. Just had another thought, perhaps my speedo is out and I am actually doing 90 mph which is why my fillings are falling out!

Check the timing on both cylinders before you start randomly buying things like a cam ring.

Are the frame and engine bolts tight?

Check your speedo against those lit-up speed warning signs.

Gearing too high is the ruination of many a bike. If you have standard gearing there is probably not much room for improvement there.

[Mosin]

I came into work today on the A7SS and made a point of paying particular notice to vibration. Most of the journey was spent between 50 - 70mph in top gear. I was amazed by just how smooth it was and was certainly not in any way uncomfortable, either through the pegs or the bars. I could have quite happily ridden at those speeds all day without discomfort. Although I should stress that it is VERY rare that I ever take the bike up to 70, much prefering to sit at a more comfortable 60.

I'm not sure if that helps at all.

[Tukig]

Hello everyone,

Please excuse my lack of response, I've been away from the computer. Thanks for all the advice, especially the offers of a comparison ride. You are right, talking about vibration is probably like dancing about architecture (may be worth an arts council grant though). I live in the NE of Scotland about 25 miles W of Elgin if any of you kind people are close. However I have been working through some of your suggestions and the timing is indeed different on each cylinder. So.... closer examination revealed play in the points plate both in/out and side to side. I can't be sure but the cam ring may have also been "attacked" in the past. The Mag is now away for reconditioning thus pleasing the gods and making the sun shine while the bike is off the road. Still plenty of other things to tinker with and lots more queries to post (sorry! and thanks!). I'll let you know what difference the recon mag makes. I am nervously hopeful.

[fido]

I live near you but my bike is a longstroke A7 so not a valid comparison. I have a friend who lives near Aberlour though and he has a suitable bike if he's got it running properly.

[Tukig]

Thanks for the offer Fido. When the bikes up and running again it would be good to try a comparison. Looking at my last post I don't know where I live! It should be 25 miles EAST of Elgin, oh well, only 180 degrees out. Doesn't bode well for my timing.

In answer to another question: Its the harsh through the bars sort of vibe.