tac ratio

[fedders09]

I am in the final hours of putting my 79xs11 back together and i was gonna put on new gauges but im not sure of the ratios, its probably somehwere here but i havent found it yet so some help would be much appreciated, its been months since ive been able to ride and its gonna be the first time with all 4 cylinders! thanks everyone

[natemoen]

The tach is electronic and runs off the alt. The speed is some oddball ratio like 1.1 to 1 or something stupid like that

[3Phase]

Evenin', Fedders, are you going to use an aftermarket tach and drive it from one of the ignition coils?

Drive the tach signal from either of the two coil negative wires, the Orange or the Gray wire but not both! The ratio would be 1:1 because it's a wasted spark system and each coil fires once every 180 crankshaft degrees.

The stock tach doesn't really have a ratio that you can use because it's driven by the alternator, not the ignition. It counts the number of pulses from one of the three stator windings and converts it to DC to drive the needle.

[crazy steve]

As Nate said, the tach is driven off the alternator and uses frequency to indicate rpm. As to the speedo, the ratio is 2.9:1...

Here's a whole discussion about this....

http://www.xs11.com/forum/showthread...t=speedo+ratio

[natemoen]

As to the speedo, the ratio is 2.9:1..

Didnt think I had the right ratio but I didnt think I was that far off, its still a stupid ratio choice thought either way!

[chanley28]

follow up question

on a scale of 1-5 what is the difficulty of this job? I am a fairly new owner of a motorcycle, so if you were to put on a new gauge, would this be something I could figure out on my own, or should I leave this up to a dealership (which I would not want to do)?

[crazy steve]

on a scale of 1-5 what is the difficulty of this job? I am a fairly new owner of a motorcycle, so if you were to put on a new gauge, would this be something I could figure out on my own, or should I leave this up to a dealership (which I would not want to do)?

Custom work is rarely straightforward, so I'd say this could rate a 3. But it depends; first, finding a speedo with the proper ratio, next, does it come with a decent mounting setup? If the latter answer is yes, it may not be that bad. I wouldn't take it to a shop (and particularly a dealer) as this could be a 2-300 dollar bill too easily; custom work is never cheap. But my experiences with 'universal' items is that usually they fit everything sorta and nothing really well, so some custom work is usually needed to make it 'right'. Most aftermarket 'universal' gauges come with some sort handlebar mount, so if you think that will work on your bike, give it a shot...

[natemoen]

Also there are companies out there that do make ratio adapters for speedos if you need one. cost somewhere around 60 - 200 bucks from different sources.