Vibration issue

[phil mcglassup]

I've just balanced my carbs in order to cure vibrations in the footrests and seat. The carbs needed minor adjustment but this hasn't improved the vibration problem.

The vibrations are only felt over about 3500 rpm, under this it is more or less vibe free. Also during acceleration there are no vibrations throughout the rev range. The large washer has already been fitted behind the exhaust mounting bolt and I've put a soft rubber washer underneath the front tank bolt which has stopped tank vibes.

I used the two jam jars with fluid method to balance the carbs and this was done with the engine at tickover speed. However, whenever the throttle was blipped, to ensure an accurate balance, the fluid levels in the jars changed quickly. Does this mean that at higher revs the carbs are out of balance ? Or is something else wrong, causing the vibes at higher revs ?

Your thoughts would be appreciated

[BBROWN1664]

With a carb tune or similar, the levels change when you blip the throttle as the vaccum changes. They should remain in balance though.

[phil mcglassup]

The fluid levels change during blipping of the throttle so that some of the fluid moved from one jar to the other. When back at tickover the fluid levels did not change or move (although they are at new, different levels afterwards)... should this happen ? It just appears to me that there is an imbalance higher up the rev range.

[misterjayb1]

Came from 09 xj6 to a foxeye (4th fzs6 iv owned). I was genuinely surprised at the level of vibes between the two. Pillion rider immediately spotted it thru the footrests. The xj was sewing machine smooth throughout the rev range. I just figure good fuel injection was the difference versus carbs. The current foxeye tach needle stays rock solid on idle so I just crack on and ride  .. ps arent carburettors usually balanced at a higher rpm rather than on idle??

[phil mcglassup]

Good point about balancing the carbs at idle. I followed the guide on the forum and it states that the process should be done at tickover. My previous bike, a gsx750f used to be balanced at 1800rpm.

I can understand that throttle bodies can be balanced more accurately and result in a smoother engine but I'm sure mine is as good as it will get....at tickover anyway 

One other thing, it has an aftermarket link pipe and silencer and the centrestand pushes against it when it is up. I'm wondering if this is causing some of the vibtation as the right peg vibes worse than the left !!

Also, there are very slight vibes in the handlebars but I read somewhere that as mine are a little bit bent, that is all it needs to set of vibrations in the bars 

[misterjayb1]

i have an aftermarket Silencer and link pipe on mine too. My last fzs was 3 bikes before this one so my memory is a little hazy.. I feel very little, if any vibes thru the bars.. The main complaint was from the pillion pegs and they are bolted directly to the subframe and perilously close to that exhaust can.. In future I may just leave her at home and ride in peace, vibes or not 

[phil mcglassup]

Mine's a single seat with no pillion footpegs ...therefore no missus on the back  ..so no problem there!!

Any other thoughts/suggestions/experiences/opinions anyone ? These vibrations are making the riding experience intolerable 

[darrsi]

Is there not a rubber bung stopping the centre stand metal from hitting the exhaust?

[phil mcglassup]

There is... but my link pipe is at a non-standard angle and I was wondering if that could cause vibes to travel from the exhaust to the frame via the centre stand. I might remove the centre stand anyway because I can't use it as the PO lowered the rear suspension 

[darrsi]

There is... but my link pipe is at a non-standard angle and I was wondering if that could cause vibes to travel from the exhaust to the frame via the centre stand. I might remove the centre stand anyway because I can't use it as the PO lowered the rear suspension 

Can you not wrap someone round the stand where it hits the exhaust, like a bit of rag or something, then take it for a quick spin and see if it makes any difference?

[Jules-C]

And check the centrestand inner or outer spring isn't broken

[Html33]

Check the bar ends and the internal weights are still in the bars. My missus CBR125 had them removed by previous owner when he put the gash grips on.
I could never notice it (or was used to it?) But the missus said when she rides her hands go numb.

Investigated, they were missing - Replaced them all

No more complaints (Well not about numb hands any way, still plenty of complaints )

[phil mcglassup]

Centre stand is fine.

The handlebars have the weights attached and an additional 25mm length of 20mm rebar added on (with hole in for fixing bolt) for good measure.

Might try filling the bars with lead shot and silicon sealant or sand, just to make sure  Would fixing some heavy weights to the outer edge of the footpegs help at all ?

I had a go on a fuel injected Triumph TT600 recently...and it was about the same as mine anyway, so maybe I'm expecting too much. It's just that previous bikes have been as smooth as silk all the way up the rev range even with no handlebar end weights !
 

[Kentish]

Lead shot? is there something we should no about you 

Anyway. You will be best of balancing the carbs with a proper balancer. Oh and fill the bars with rubber.....