Kph speedo

Twin Pots

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As with probably all Triumphs here in Oz my 1967 Bonneville is fitted with the correct 10 - 150 mph speedo. I finally got hold off a Kph speedo 10 - 190 from the US which I really wanted to fit as we ride to Kph here in Australia.
Supposedly renovated it turned out it was not. The US supplier was great and gave me a full refund inc postage and let me keep the speedo. I have never seen another Kph speedo for sale so I reckon this is quite a rare beast. This is an original Grey faced Smiths speedometer.
I took it to a local specialist who did a full rebuild. He did mention it had 1600 gears inside whilst the dial face said 1000. They stuck with the 1600 internal gears. I have now tried using the speedo with both 1.25:1 rear wheel drive and a 2:1 rear wheel gearbox drive. Neither seems to give anywhere near an accurate reading at the speedo. Does anyone out there have experience with the Kph speedo?
Do I need to return it and have the 1000 gear internals fitted to make it work? i have already spent $350 on the rebuild.
 

grandpaul

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Should have had him replace the gears on rebuild; too late, I know...
 

Rocky

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For what it's worth, Canada is metric too and all the old British bikes are in MPH on the speedo.
I don't think anyone here goes to the trouble of making the change to KPH and we don't seem to have any problems with sticking close to the speed limits - well..... fairly close BGRIN
The only answer for you is to have the speedo converted if you have tough cops and an accurate speedo is a must.
Otherwise, I would leave it since you've already spent a lot on it.
 

grandpaul

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Take it out following a second vehicle; lead vehicle gets up to 40 KPH and signals, holding it there for a kilometer or so. Remember the indication or mark speedo bezel with a grease pencil or crayon. Do the same for 80 and 120.

Take some wide clear cello tape and stick over the bezel, mark with permanent sharpie, with extrapolated intermediate markings as you wish.

Ba-ding-bing!
 

Rocky

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GP, you're a wizard!
That was going to be my next suggestion BGRIN

Up here, if we're in a 90 KPH zone all we do is multiply the 9 by 6 - 6x9 = 54 (54 MPH)
If we're in 100 KPH zone, multiply the 1 by 6 - 6x1 = 6 (60 MPH) and so on.
It's second nature to us now.
 

grandpaul

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By the time I finished cipherin' the maths, the cop would have pulled me over...
 

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Twin Pots

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Thanks for the replies. I had been using the original 150 speedo with markings but really wanted a Kph. Although listed in the Triumph parts catalogue there seems to be almost no information (read nil) for this speedo or where it was used. As I said it seems to be a very rare item so it would be good to get it working correctly.
 

harper6t

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Where are you located ?
I have a friend in Western Sydney who does up instruments, if the face is available its not a big issue to replace the face and change over the gears to get the correct ratio.
get back to me if you want his details
There are a stack of different options for the Smiths Shallow Magnetic speedo, so it could be a chore actually tracking down the correct dial to match your tacho dial, but there are people out there on the internet who make replacement dials, they are after all only screen printed on a metal disc with appropriate cutouts for the odometers.
It's my understanding that the odometers are ruled by the gears in the unit and the needle for the speed is set by varying the magnetism (adding or subtracting magenetism in the magnets on the shaft) and the fine adjustments are by varying the closeness of the speedcup to the magnet.

With 56 years riding experience you should have a fair idea of the approximate relative speeds anyway 100kph = 60 mph, 80 kph = 50 mph, 60 kph = 35 mph, 40kph = 25mph.
Not that these old speedos are going to be exact across the whole range in any case even when restored.
 

Twin Pots

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Thanks Harper, appreciate the info and offer of help. I am going to start by taking the speedo back to Ottos(specialist close to where I live) who I paid the $350 to fix it !! Mine currently geared to 1600 when I think it should be 1000 as shown on the dial face. I suspect Ottos can't get the gears which begs the question how do they fix a worn speedo. I do have the original the bike came with which has the 1000 gears but a shame to ruin a perfectly good speedo. It would be really helpful if you could ask your friend if he can get new 1000 gears for this instrument. A word of caution on accuracy, two weeks ago a friend in Melbourne received a speeding ticket for exceeding limit by 4 kmh.
At least with a digital speedo you can see the numerical speed but on a typical old Triumph speedo ( analogue too on my FJR 1300) that equates to 1 or 2mm of needle movement with no cruise control plus we all know bike speed can vary a few k's up and down in a split second, hardly a hanging offence and certainly not fair. Hands up all those with an old magnetic speedo that doesn't flicker 5 or 10 km either side of your speed.
Harper you also asked about condition of my speedo. It looks like new and works really well apart from not being at all accurate with the current 1600 gears. When I am doing 80kmh the speedo is reading 50kmh. Unless someone with far superior maths skills than me (so that would be a great many) tells me I am wrong I'm hoping 1000 gears would make it work properly
 

harper6t

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If at 80KPH its reading 50, then its reading correctly for Miles Per Hour at that point. Is it reading 35 at an actual 60kph ? if not it may not be a simple calibration error but something else.

The 1000 and 1600 are the number of turns of the cable for one of the units, 1000 turns per kilometre or 1600 turns per mile, this 1000 to 1600 is the approximate ratio between a kilometre and a mile
e.g. 1 mile = 1.60934 Kilometres.
The gearing only relates to the odometer. But as you have the 1600 gearing it would be a mph unit and I suspect the person working on it may have set it up to read miles per hour by the dial.

Apparently the main way to adjust these speedos is to change the strength of the hairspring which is attached to the shaft

The 2:1 drive is the correct one for your 190 kph/120mph speedo, the 1.25 :1 is for a 240kph /150mph speedo.

It's very difficult if not impossible to get one of these speedos to be reading correct all throughout its entire range and you may need to have them set it as correct for a particular speed
e.g. set to be correct at 100kph it reads 100, but at 80 it might read 78 and at 60 it might read 57.

Victoria is treacherous for speeding as they only allow 3kph before booking you no matter what speed limit, at least in NSW its normally 10% before they book you with the cameras and more when a policeman has to pull you over.
 

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It looks like new and works really well apart from not being at all accurate with the current 1600 gears. When I am doing 80kmh the speedo is reading 50kmh. Unless someone with far superior maths skills than me (so that would be a great many) tells me I am wrong I'm hoping 1000 gears would make it work properly
Twin Pots, your assumption is correct, mathematically. 50 kph is 5/8 (.625) of 80 kph, and a 1000 gear is 5/8 (.625) of a 1600 gear, so changing the gear should put things back in the proper range. However, I believe the gear teeth on the 1600 are smaller than the teeth on a 1000, so it would likely be a matter of also changing the gears that interact with the main gear.
 

Twin Pots

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Many thanks to both of you for taking the time to respond, I really appreciate it. I do like Greyfells answer ever so slightly more as it confirms what I hoped was happening. I now need to speak with Ottos and see how much they will sting me to correct the problem which they should have known the first time at $350. They are the experts , not me.
Harper, I would really like the contact details for the chap in Sydney who does this work.
3kph over at say 100kph, that's accuracy that only a robot could guarantee. That should be challenged in court as being inhumane. Never wanted to live in Victoria anyway and aren't the Victorian Police under investigation for corruption?
 

grandpaul

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I wonder how a "reasonable" judge would consider an honest request for leniency based on the mechanical limitations of an old speedometer on an old bike that isn't honking down the lane at 140KPH, but bimbling along at 55KPH when the speedo is reading 50 per the posted limit?
 

Twin Pots

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Exactly! I just hope its not me that puts it to the test. If anyone out there has contacts that can say whether or not these speedo gears can be purchased new it would be helpful. To differ the ratio they have to come in pairs, a normal straight cut gear and a helical type gear. The speedo is an original Grey faced Smiths SSM 5001/01.
Wishing you all safe & happy riding.
 

grandpaul

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The guy that used to do all my meters had a test rig. I mean, if you are going to pay $300, it darn well better do what you paid for it to do!
 

harper6t

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Many thanks to both of you for taking the time to respond, I really appreciate it. I do like Greyfells answer ever so slightly more as it confirms what I hoped was happening. I now need to speak with Ottos and see how much they will sting me to correct the problem which they should have known the first time at $350. They are the experts , not me.
Harper, I would really like the contact details for the chap in Sydney who does this work.
3kph over at say 100kph, that's accuracy that only a robot could guarantee. That should be challenged in court as being inhumane. Never wanted to live in Victoria anyway and aren't the Victorian Police under investigation for corruption?
My friend who does up instruments is
Peter Boros Ph 02 9920 6658
He has the test bench etc to set the speedo, but as he will tell you, if it is set to be accurate at 100, it may not be exact at 60, because of how these instruments work which is primitive because its relying on a spring and magnets and not gears as in a chronometric speedo. (see my previous posts - on a magnetic speedo the gears only control the odometers for miles travelled and not the indicated speed)There are other variables such as the rolling diameter of your tyre, so when he sets the speedo its at the specified revs of the drive cable as it was originally designed or as close as he can get it, but whether its absolutely accurate on the bike with whatever tyre and rive unit you have is an unknown.
It should however be a lot closer than you are quoting.

I think you might have to have to get the gears made up if you wanted new ones as they wouldn't be available from Smiths, there are companies who can make the gears but generally you would get a set from an otherwise wrecked instrument.
 

grandpaul

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Most of the good rebuilders have stashes of spare internal parts. I know Joel Levine could build any Smiths meter you asked for, at a price. Of course it drops significantly with a good core.
 

harper6t

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Most of the good rebuilders have stashes of spare internal parts. I know Joel Levine could build any Smiths meter you asked for, at a price. Of course it drops significantly with a good core.
Yes, a stock of spares is essential, I am storing the bulk of my friends japanese instrument spares and that is a couple of thousand instruments for just the ones he doesn't get to restore very often, not including the CB750, Z900 or GT750 units which are the bulk of his japanese bike work.