rev counter fluctuating

[johnA]

hello gents the rev counter on my gpz 1100 unitrack started fluctuating the other day while the engine revs were constant could anyone tell me if its a sign of the coils breaking down or is it just a problem with the rev counter. its not doing it all the way through the rev range just under 4000 revs with no noticeable miss firing.
many thanks for your help in advance john

[8 Valve Mark]

as the engine tickover is constant,it's likely a tachometer/drive problem.

[zed1015]

Electronic Tacho.
Might be a dodgy connection or needle dampener.

[johnA]

thanks for your replies gents.

[Al]

My J tacho ( same components but arranged differently on a different shaped board) had gone bonkers twice. In both cases it was caused by the live wire feed to the coil breaking. The tacho as you pointed out is fed from the coil so any interruption to the coil feed supply is going to have that effect. The tacho takes its signal before the coil is triggered so it may be a failing coil but my guess would be the wire that feeds the tacho itself, or as was stated above a failing 'tacho board' or needle / magnet combo.
AL

[johnA]

thanks for the info Al will get the tank off and check the wiring.