Modern Instruments On Vintage Daytona ?

Discussion in 'Vintage Classics' started by Gary Lovell, Jul 25, 2020.

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  1. Gary Lovell

    Gary Lovell New Member

    Jul 20, 2020
    The Villages, Fl.
    Has anyone tried using modern electronic tach / speedometer on our vintage Triumphs ?
    I have been told our speedometer is notoriously optimistic .
    I also wondered if the modern tach would work since it records the interruption of pulses at the coil .
    I’m not very good on electronics but this might be an interesting non permanent inexpensive choice to simply give a try - - .
    My eBay bike has me wondering about many items . Excellent rims and spokes , great seat, carb slides very nice , Dunlap K70 tires with good tread but tires checked all over that were made in Great Britain . Speedo works and says 6779 miles . Pistons new, bore too tight(.003 clearance) but obviously fresh +.020 .
    Thanks for reading . Gary from Florida
  2. EJT

    EJT New Member

    Nov 23, 2019
    Michigan US
    Have no idea where I saw it now but whit in the last day or so came across a website that was selling a electronic speedo kit that used a sensor at the rear wheel. Maybe used the original drive?
  3. BrianG

    BrianG New Member

    Jul 25, 2020
    West Sussex UK
    Hi Gary,
    Quote: "I have been told our speedometer is notoriously optimistic".

    I have a 1969 Daytona which was rebuilt in 2000 and had a new Smiths Tacho and Speedo fitted. In the UK we occasionally have temporary radar speed check signs mounted on street lamp posts that have large LED displays. These show that, for my speedo at least, it's accurate at 30 and 40 m.p.h. to within about 1 m.p.h., so they are not always unreliable. I also feel the tacho is correct within about 5% overall agreement with the speedo reading for the gearing. (Depends how much the vibration affects the needle position!)

    The overall accuracy can be affected quite significantly if you change the tyres for more modern metric profiles. Some can be an inch or more smaller in overall diameter, giving an optimistic reading. I know you have the K70s at present, so when I was looking for new tyres I looked for ones with the same diameter on the rear and fitted a Dunlop K82 (same tread pattern as the TT100 K81) on the rear which kept the speedo calibration the same.
  4. BrianG

    BrianG New Member

    Jul 25, 2020
    West Sussex UK
    I don't know if you are new to British bikes, but I forgot to say that as you have got the bike from eBay have you checked the age of the K70 tyres from the date code on the sidewalls? I would not recommend using tyres that are more than 10 years old as with age they can get very hard giving poor grip and can suffer unexpected cracking. If there is no date code then they are definitely more than 10 years old!
  5. Gary Lovell

    Gary Lovell New Member

    Jul 20, 2020
    The Villages, Fl.
    No date code on tires “ made in Great Britain “ last title was 1978 . Thanks for info .
  6. Yorkshireman

    Yorkshireman Crème de la Crème

    Dec 12, 2015
    Date codes are on all tyres as far as I know and look like this
    This tyre was made in the 47th week of 2020
    Haven’t got any British tyres, just French and German.
  7. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    appalachia usa
    #7 speedrattle, Jul 4, 2021
    Last edited: Jul 4, 2021
    your daytona's electrical system will be positive ground, and any modern electronic instruments will be negative ground. so long as the modern instrument is insulated from the frame, you can run it, if you remember to hook the feed and ground wires to the instrument in reverse. a dedicated pair of fused wires to the battery is least ambiguous.

    i have run an electronic speedhut GPS speedo/tach on a 1972 and a 1965 triumph bonneville, both converted to negative ground. it worked okay, but the GPS unit was picky about the vibration and kept shutting off. maybe a non-GPS unit would have worked better? other people run electronic clocks in their machines without any difficulty.
    • Agree Agree x 1
  8. Iron

    Iron Guest

    #8 Iron, Jul 21, 2021
    Last edited by a moderator: Jul 21, 2021
    As SR says above. Wiring to electronic speedo is pretty easy, some will need a permanent connection to positive and another positive from the ignition, then a negative connection. You'll need to think this through if you still have positive ground.
    The speedo can be a GPS but I've used magnets and a sensor.
    The magnets are picked up by the sensor and the speedo figures out how fast you are going by knowing the circumference of the wheel you are using and how many magnets you've put on the wheel. These are entered into the speedo once installed through an easily understood single button menu. I thought it would 'forget' the mileage if the battery was removed but it doesn't. I've no idea how it remembers but it does.
    You can see the magnets I've put into the rear sprocket. (Drilled some shallow holes and stuck the magnets in). You can also see the sensor on it's ugly bracket. (I'll sort that out when I reweld the joints on the sissy bar and include a bracket and grub screw to hold the sensor) But it gives you the idea.
    There's no reason to drill the sprocket or brake disc if it has some convenient places for the magnets. I've drilled the bolt heads on discs in some cases. The more magnets, the more accurate is the speedo as it can read changes quicker.
    They are miles better than the mechanical ones and they light up pretty when you turn the key. I go for the cheap ones at about £70 a pop that include brackets, magnets, sensor etc. But I'm not looking for dummy lights (neutral, indicators, gear selection etc) nor do I look for a rev counter (my ears work and I'm not racing) I just go for the basic speedo. I used to run without a speedo but with all the cameras about decided to have something that works and didn't rely on engine gearing or the correct speedo drive on the axle.


    This is on a T120V custom, I also have the same unit on a standard T140V but with the magnets in the bolts on the front disc.

    Bugger, just noticed I'm a year late. Soppy :rolleyes:
  9. Cyborgbot

    Cyborgbot Guest

    Modern instruments on a Triumph… A Sequential Prophet-5 would look very silly on a vintage Daytona and would be very hard to play whilst negotiating hairpins.

    Stick to vintage instruments like a harpsichord or harp for better safety and aesthetics.
    • Funny Funny x 3

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