I have a 1988 Yamaha FZ600 and whenever I am in gear and the

[Geoff M]

tachometer gets to around 6500 rpm's the bike? lets go of the gear and just rev's all the way up until I let off the gas.  Is this the Rev Limiter kicking in?  If it is doesn't that seem pretty low on the tachometer to be the limit?  Is there any way to take this off?

[u must be bored get a lif]

sounds like a tranny problem . that's  not how a rev limiter works

[YZF750R]

sounds like the clutch is slipping.

If it only happens in a specific gear, that gear may be worn out.