Re:tachometer v.s speed

[blacktrain]

hi,i installed a aftermarket tach as it was missing when i got the bike ,just went for ride at 70mph i was at 2,000 on tach does this sound about right  1997 ct

[WintrSol]

You are going to need the diameter of that tire, relative to the diameter of the stock tire. On Metz 880 tires, I get about 22mph per 1000rpm in top gear, so 66mph is about 3000rpm.

[Tourus]

      My 2000 Tourer @ 3000 rpm is going 65 mph very consistent
     Actual speed according to my GPS would be 63mph
     Stock tire size on front

[DGS65]

Does this tach have a cylinder setting?  I may be set incorrectly.   
I agree with the figures above this seems very low for 70 I think it should be more like 3500 or higher at 70 mph

[Fireman973]

75mph and I was at 3400rpm or there about stock 1999 IS.

[indybobm]

Because each spark plug fires on both compression and exhaust cycles you might need to set it for 3 cylinders? Just a thought

[LB]

2000 rpm = 45
2500 rpm = 55
3000 rpm = 65
3500 rpm = 75

Stock bike.

[John Schmidt]

Hook it up like an old dwell/tachometer gauge used to set points back before everything was solid state ignition(assuming you're over 60  ). One lead on the coil, one to ground, and I believe one to 12vdc. It's been quite a while since I've used one....a loooong while, so the connections mentioned might be a bit hazy. What does your aftermarket tach have for wiring, and are there instructions with it. I hooked an aftermarket tach up to my GL1200 restoration project, only used three wires. Don't try to hook it up using the OEM tach wiring, been there, done that....didn't work. My friend's Valk had an aftermarket on it and the first person to try and hook it up had it showing over 9k rpm at idle. If memory serves, I put one lead on the front coil under the tank, one to 12v and one to ground. Works great.

[blacktrain]

hi,  tires are front-150-80-17 rear-90B-16. put my gps on  at 70mph i was at 22-2300rpm seems the speedo reads about 4mph fast, i install a bosch -fst-7903 tach from jegs preformance. has a 4-6-8 cyl option i have it on 6 mabey i will try 4or 8cyl see what happens. says 600rpm at idle ,

[WintrSol]

I'd choose 4. A 4-6-8 tach set to 6 is assuming 3 sparks per revolution, which is what a 6-cyl car would provide, and when set to 4 it will expect 2 sparks per revolution. Since a single coil set on the Valk fires two times per revolution, that setting on the tach should show the correct rpm.

[blacktrain]

 yes sir , i set it to 4cyl will go for ride in a.m . let you know thanks

[blacktrain]

hi, that did it ,set it on 4cyl works great . thanks for the info