1. 

   Bryce Member Premium Member

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   81 gsx250

   I'm hoping someone can help me out as I want to get a aftermarket tacho but need to find out what ratio gear drive I have. It's a 1981 gsx250 and my options are 1:4, 1:5 or 1:7

    

   Bryce, Feb 5, 2015

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2. 

   Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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   My Bike:

   1937 Royal Enfield 250, CF Moto 250 V5, Honda's XL250, CBR250, FT500 plus a few others.

   Clean the end of the tacho cable and wrap a piece of masking tape around it leaving a piece sticking out like a little flag. Take off necessary cover to get to nut on end of crankshaft and fit a socket on a fixed bar, then rotate the crank 10 times and count the turns of your tacho cable flag. This will give you a ratio, ie 10 crank turns to 2 cable turns = 5 : 1.

    

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   Murdo, Feb 6, 2015

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3. 

   Brett GSX Member

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   Hi Bryce. Tach ratio is 1:4. I tested the mechanical aftermarket one I bought against the electronic tach the guy before me had wired in, and RPM were identical.

    

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   Brett GSX, Mar 2, 2015

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4. 

   Bryce Member Premium Member

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   Thanks Brett! I have sold the bike since this post but cheers for the help.

    

   Bryce, Mar 2, 2015

   #4

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