A2 KLE500 grinding noise between 4500-5500 revs

[jimbob92]

Hi,
Just a quick one really, had an A2 kle500 for about 6 months now, about 45,000 on the clock but been well maintained and has been running smoothly. BUT the past couple of times I've taken it out it's been making a strange grinding noise between 4500-5500 revs. It doesn't effect the acceleration or performance in any way and only happens when the bike's in gear. It's bloody irritating and it's got my dad baffled who's owned and worked on bikes for 35 years. Any ideas or advice greatly appreciated.
Cheers.

[tomh]

It's sounds like something is loose on the bike, going over most major bolts checking they are fully torqued out will help.

A loose swing arm pivot bolt caused a horrible grinding noise for me at higher rpm that I was convinced was coming from the engine.

[stinkwheel]

So always at the same rev speed?
In every gear?
Never when in neutral?

What about if it's in gear with the clutch pulled in?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[jimbob92]

It does it in neutral as well I've found, but i think I've found the problem, the header pipe is cracked right round underneath and seems to be blowing out at them revs, hopefully once I've sorted that it'll be gone.

[Benjamin_Breeg]

Did you sort this out?

Just my GPZ500 has developed a similar sounding noise at about 6500 rpm.
It happens in all gears, as well as with the clutch pulled in, but also happens in neutral.
I think I've tightened all major blots, but to no success.

Cheers.

[jimbob92]

The cracked header pipe was the problem, got it welded up and the noises stopped! thanks for suggestions everyone