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Electronic tachometer strangeness

J

jforgo

New member
I have a 1982 R100RT, running a 400x18 Avon Roadrider in back. Bike has the stock 32/11 rear end, and 1.078 speedometer. I know the Motometer speedometers are not the pinnacle of accuracy, but I typically show about 4100 RPM at about 70 mph in fifth. This morning it was showing 5500 RPM at 70, and the tach needle was not being shaky. This afternoon the ratios were back to normal.
What is going on here?
 
Last edited:
You sure you weren't running in 4th gear? ;)

Could be a loose solder connection inside teh tach. If you are handy with a solder iron I would open the case and resolder all connections.

/Guenther
 
I have read that the higher RPM is caused by a faulty capacitor on the tachometer circuit board. Mine has temporarily jumped to higher RPM's; riding the bike seems to help that problem which indicates a connection problem to me. If I can't get the problem to repeat consistently, I work on ignoring it. Good luck!
 
Ya, I had thought I forgot to shift, too. Long days, not enough sleep can make me dingy, but 4thgear it was not.
 
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