Vibbey and sounds rough at 5-8k revs nc30

[Rick1138]

Hi all,

i ahve noticed that my bike seems to sound a bit rough at anything between 5k and 8k revs.

I get full power from the bike and it revs freely, however when i am sitting at say 65 in top i am usually at this rev band area, and i get a vibbey feel through the handlebars and foot pegs.

I am not sure if the bike is supposed to do this, but it makes my throttle hand go numb in the thumb and index finger faster than you would expect on a cramp sportsbike.

A guy on a local forum said the this was a common issue, and that it had been discussed on this forum, although using search function has netted me nowt.

Can anyone help as i hate my hands going numb after about 30 mins, and i don't like the bike feeling rough.

the airbox is clean and the chain is new, and adjusted properly, a friend said the front sprocket may be the cause of vibration but i don't know how.

Cheers for any help all.

[fumb]

Have you got standard bar ends fitted?

[Rick1138]

no they are oxford ones.

but i doubt that they would be the cause of vibration in the footrests aswell as handlebars.

why do lighter ones cause issues?

[fumb]

Well, bar ends are designed to take certain frequencies out of the bars and stop the 'viby' feel. Lighter ones may reduce this effect. Like you say though, it shouldn't effect your pegs.

A few quick thoughts... has the engine been out? been put back correctly with correct mounts and not fouling the frame?

Has the exhaust been mounted correctly? has it got rubber grommets bewteen the hanger and exhaust bolt?

work a quick glance maybe.

[Rick1138]

Yes these are all fine.

i had a small off earlier in the year and checked everything over after that and it had new suspension fitted so i checked clearances etc.

My first thought were that it could be needing its valve shims done as its just hot 25k miles on the clock.

My other idea was to check the carb balancing.

As the bike only gets used at weekends when i get a chance (only see GF at weekedns so time is split!), the carbs may be needing a clean, but before i go down that route i wanted to see if anyone had any other suggestions.

cheers

[CMSMJ1]

Simple answer is to change down a gear and rev thorugh the rough spots. I don't think it should vibrate bad enough to cause numbness though!!

Are your wheels balanced? Have you checked them since your little off?

[Rick1138]

i get numbness in my right hand on all bikes i have owned, just a fact of sportsbike riding position i assume.

Its not so rough as to affect the bikes ride, its just disconcerting. And as its getting to that stage of shims etc, i was just wondering if anyone had had a similar issue.

[Cammo]

My other idea was to check the carb balancing.

I think you're on the right track here.

I would guess that the fuelling is a bit fluffy at these revs, manifesting itself as vibration through the frame, etc. There doesn't have to be much to notice it, just the right frequency.

Is the jetting standard? The bikes do run lean in this exact rev range, you can cure it by raising the needles 0.5mm over standard height. I reckon doing this combined with a carb balance (and valve check for peace of mind - it's due!) will cure it. New plugs might help also, but only do them as a last resort.