rev counter

[Curly]

hello
On the way home last night, i was in 5th gear when i noticed the rev counter drop to zero the back up 7000 revs. It did it once more about 5-10sec later. I did hold the bike at different revs to see if i could get it to repeat but its been fine since ?? Ive read about error codes but thought these showed when the bike was stationary ? any ideas ?
gen 1
cheers matt

[slappy]

Possibly sticking exup,  might need checking and lubing, be careful taking the bolts off, use plenty of  WD40 or similiar.

[RMT1983]

Definitely exup..................... Good luck mate!!!

[Curly]

Got home last night and the Rev counter is flicking to 7k at a standstill. So ex up confirmed. Had a look this morning and the centre nut on the pully had come loose Everything out, cleaned, re-lubed and back in. Job done, I hope