Bouncing or "fluttering" from rear wheel.
 

My Son reports that he is getting a bouncing or fluttering sensation from the rear of his bike as if the tyre was leaving the road.

It only happens in certain conditions at around 50-60mph, and is around 2-3 times second.

Bike is an '08 plate with 1700 miles on the clock, it has been SORN since August 10, so has been stood around a lot.

Does anyone have any suggestions what this could be?

rear shock failure (unlikely at 1700 miles) or settings is the first thing that springs to my mind.

Re: bouncing or "fluttering" from rear
 

...or maybe a distortion of the rear tyre from standing?

Re: bouncing or "fluttering" from rear
 

most likely this, as it has been sat around for nearly 18 months. Take the back wheel (with tyre still on) to a tyre fitters and ask them to check.

Re: Bouncing or "fluttering" from rear wheel.
 

I'd say it's a lot easier to twiddle the adjusters before taking it down to a tyre place. I can't really see how they'd spot something that you can't. I don't think it'll be the tyre of its only doing it at a certain speed.

Re: Bouncing or "fluttering" from rear wheel.
 

Obvious, but check tyre pressures too.

Re: Bouncing or "fluttering" from rear wheel.
 

Pressure is 36psi, that should be okay shouldn't it?

I have mine set to 33psi front and 36psi rear so that sounds perfect.

As said before, check for alignment and distortion

Re: Bouncing or "fluttering" from rear wheel.
 

Car I'm using at the mo was off the road for 12 months .
All of its tyres were flat. It's very odd feeling at 70 ish were they have flat spotted , drive at 60 its fine .so can be were it was left .tried balancing .pumping them up harder. Still the same 2 months on

Re: Bouncing or "fluttering" from rear wheel.
 

Back end up on a stand, unbolt the rear caliper and hook out of the way with a bungee, slacken off the spindle to push the wheel forward, unhook the chain from the rear sprocket and push to the side, spin the wheel. Look for distortion of the tyre.

Going to a shop means taking the wheel our or paying them to do it so you may as well try it yourself first. If they had any sense the shop will simply eyeball it just as you can. The balance machine and fresh weights will not fix this if it's a flat/deformed tyre so if you go to a shop and they head straight for the machine be wary.

Re: Bouncing or "fluttering" from rear wheel.
 

Unless they spin it up on the machine and hold something near the tyre and eyeball it that way...

There is nothing stopping you doing the same with the back wheel off the ground on a paddock stand and spinning it up with the engine, just dont get near the chain or use anything sharp. If there is a lump or flat spot then you can gently let a bit of chalk rub the tyre to mark it but use a bit of caution/common sense working near a spinning tyre.