Tacho problem - GS550?

[OzJavelin]

Not really electrical (mechanical?), but couldn't think of where else to put this?

The tach on my '79 GS550 is playing up - reading slow and moving slow. I've replaced it with the one from my "in-progress" '78 GS750. I'm looking at the unit and wondering if it can actually be repaired easily or if it's just easier to get another one?

Any thoughts/comments?

[mikenh]

Hi,

I know this is an old thread but I am having the same issue and ran into this:

http://www.motorcycleforum.com/showthread.php?t=94629

I am slowly getting a 1977 GS550 running again and have a slow tach. I will try this out and submit a follow up post. It may take a month or two as the bike is 200 miles away and worked on intermittently.

[Brendan W]

Is the needle jumping at any stage? If it is the most likely cause is wind up of the cable. I tore into my tacho and found a lot of interesting stuff, becoming an expert bezel crimper en route. It was unneccessary.
I should have attended to the cable first and maybe shot a little light lube into the tacho input spindle.
Magnets have been reported as 'going off'.