Author Topic: ‘73 TX500 Speedo/tachometer ratio?  (Read 950 times)

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Offline bradcj85

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‘73 TX500 Speedo/tachometer ratio?
« on: February 16, 2018, 11:43:25 PM »
Swapping out for one a smaller sleeker look. But can’t seem to find clear indication on what the ratio is. Have seen 2:1 and 5:1. Anyone know for sure?

Offline dailydose1

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #1 on: February 16, 2018, 11:50:46 PM »
Speedo is 2:1 and tach is 5:1

unless someone else wants to chime in im 95% certain thats right

Offline CrouchyUK

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #2 on: February 17, 2018, 10:12:14 AM »
On a phone at the minute so if the link below does not work then search “tach ratio” here in the forum.  I never looked much at the speedo ratio, but the Rev counter ratios changed with the oil pump upgrades and were never those suggested above?

http://www.xs500forum.com/index.php?topic=1034.msg8988#msg8988
1975 Honda CB200T (2) - 1975 Yamaha XS500B (2) - 1976 Yamaha XS500C
1977 Yamaha RD400D - 1977 Yamaha XS500D - 1978 Honda CB550K - 1980 Honda CB400N
1980 Honda CB900FA - 2000 Kawasaki ZX6-RG2 - 2002 Suzuki GSX-R1000K2

Offline dailydose1

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #3 on: February 17, 2018, 07:10:08 PM »
I thought I read somewhere that dean said tach was 5:1 but maybe I was wrong. I have also seen this site:

http://mostynindustries.com.au/speedo-tacho-ratios

Offline CrouchyUK

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #4 on: February 17, 2018, 09:05:52 PM »
You were 95% sure!   ;)

All in the link I posted- later tacho's have the 3.038:1 ratio printed on the dial, early TX tacho's do not, but had a slower oil pump anyways so different ratio. 
1975 Honda CB200T (2) - 1975 Yamaha XS500B (2) - 1976 Yamaha XS500C
1977 Yamaha RD400D - 1977 Yamaha XS500D - 1978 Honda CB550K - 1980 Honda CB400N
1980 Honda CB900FA - 2000 Kawasaki ZX6-RG2 - 2002 Suzuki GSX-R1000K2

Offline dailydose1

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #5 on: February 17, 2018, 10:13:42 PM »
Hey at least im trying to help and be active on the board.....can't say the same for many others

bradcj85 I have a 2:1, 5:1 and the stock. I will try both and see what works when I get this bike running and can let you know. not sure how long that will be but hopefully soonish

Offline bradcj85

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #6 on: February 21, 2018, 02:38:14 PM »
Thanks guys.

@crouchy- the link you provided is talking to later TX models, more specifically the 78. As mine is a '73, is the ratio still 3.038?

Offline CrouchyUK

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #7 on: February 21, 2018, 06:19:51 PM »
No, I think we are reasonably sure that the C, D and E models used a 3.038:1 tacho.  But the earlier bikes had a slower oil pump, which is the same shaft as the tacho drive.  As per the link I gave- I tested a XS500B way back by rotating the engine a few times and measuring the output.  I got 4.10:1.

It will be interesting to see dailydose1 try his various ratios, as even if not correct it will check my own calculations.  I think the 5:1 comes from many other Yamaha models of the era- certainly the XS750 was 5:1 as were later Xs650's.....

1975 Honda CB200T (2) - 1975 Yamaha XS500B (2) - 1976 Yamaha XS500C
1977 Yamaha RD400D - 1977 Yamaha XS500D - 1978 Honda CB550K - 1980 Honda CB400N
1980 Honda CB900FA - 2000 Kawasaki ZX6-RG2 - 2002 Suzuki GSX-R1000K2

Offline dailydose1

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #8 on: February 23, 2018, 08:54:54 PM »
Any luck finding any 3:1 tach?

Offline nk140

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Re: ‘73 TX500 Speedo/tachometer ratio?
« Reply #9 on: April 16, 2018, 06:15:50 PM »
I just bought a 1:5 gauge for my 73 TX before reading on here. I will write back with results.  I am in the process of getting this basket case running.
« Last Edit: April 16, 2018, 06:19:05 PM by nk140 »