What tach do I need for my '52 International?

I'd like to procure a tach drive mag chain cover, or modify my stock cover to run a Chronometric tachometer on my '52 Model 30/International. I don't know if it's correct, but I do have an NOS Smiths bronze-bodied 1506/00 tach drive (same as the 70549) that I'd like to use. It's a reversing 1:1. Anyone know what tach might work with it? Thanks in adavnce.

Internally, chronometric speedos and tachos are the same, only without the odometer bit.
And the face changed...

So if it spins the right way, you can connect any speedo and see whats what.

Most of the tacho drives mounted on the timing case of old four strokes are geared two to one with respect to the timing gear, so the tacho itself has to be four to one to represent crankshaft revs. The tacho off an RG250 Suzuki has the correct looking rubber mount for an early racing bike, and the gearbox on the back of it is reversible by removing two screws and turning it over. Every chronometric tach I've ever used has been killed by vibration sooner or later. The Suzuki tach is rotating magnet and they really look the business. (they look like they belong on a 1955 Gilera.) Try to buy one with no 'S" on it's face, you can't get the unit apart to paint it out. You will find that the mount uses four small cap screws to hold it to a normal tear shaped tag mounted on the top of your forks. I've bought two of these so far, neither cost more than $50.

Would you possibly please post a photo of your inter, I'd love to see it !

Any of the std Inter parts suppliers should have the timing cover ye seek.
Interested how the tacho drive is driven off the magneto drive ??

Thanks Rohan. Is that the same cover that Paul Norman offers on the RacingNorton site? Looks pretty nice- let me know if you're interested in selling it.

Hi LC,

Maybe these blokes can help, have a look here http://www.pushrod-performance.co.uk/service4.htm

Webby

I sometimes kick myself for walking away from a bargain. A couple of years ago I was in a shop near my home looking at a lot of old motorcycle bits, and there was the racing tacho drive f or $40. I know that I should have bought, and I knew then, but I still walked away because I didbn't anticipate using it in the near future. Silly stuff.

acotrel said:

Most of the tacho drives mounted on the timing case of old four strokes are geared two to one with respect to the timing gear, so the tacho itself has to be four to one to represent crankshaft revs. The tacho off an RG250 Suzuki has the correct looking rubber mount for an early racing bike, and the gearbox on the back of it is reversible by removing two screws and turning it over. Every chronometric tach I've ever used has been killed by vibration sooner or later. The Suzuki tach is rotating magnet and they really look the business. (they look like they belong on a 1955 Gilera.) Try to buy one with no 'S" on it's face, you can't get the unit apart to paint it out. You will find that the mount uses four small cap screws to hold it to a normal tear shaped tag mounted on the top of your forks. I've bought two of these so far, neither cost more than $50.

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Acotrei - do you have a photo of your RG250 tacho face? Do you happen to know what year and model yours are from? Or is there a Suzuki part number stamped on the clock somewhere?

Dave

This is the one on my Seeley Commando 850:

This is the one on my two stroke:


1983 RG250 Gamma:
http://www.suzukicycles.org/photos/RG/R ... s7_750.jpg

The tacho and mount looks like it is off a fifties Italian TT machine. - Ring the wreckers, nobody wants them so they are cheap and they really look the part. Most people don't get close enough to notice the word 'Japan' and realise the fact that they red line at 12,000 RPM. I remember seeing that sort of mount and the tacho with the reversible rear gearbox way back in the old days on the really good racing bikes. Most young guys wouldn't recognise what they've been copied from by the Japanese. I am usually fanatical about never using obviously Japanese parts on my Seeley Norton, but I've made an exception with this, it is so correct in every other way. Pity the bezel doesn't screw off or I wouuld have painted out the Japanese markings with matt black paint. Don't buy one with the Suzuki 'S' on the face, it is too obvious to use on a classic bike. When I bought the second one, I showed it to a young guy who also races. He said ' it looks like a piece of shit'. After it had had the dirt removed from it, it looked like a million bucks to me ! The RGV250 tacho is electronic, so useless for your purposes.

Very useful information, Acotrei! Thanks for taking the trouble to post the pics.

Cheers, Dave

My pleasure, Dave. The RG250 tacho is the fifties European style. The Manx Norton had similar rubber 'O' ring suspension, but it was a deep conical shape, and you would be looking at up to $1800 for a replica. When you see the RG250 tacho on your bike you will be stoked. Note the shape of the mounting plate. The first one I bought fitted the standard mount on the Seeley Mk3 frame almost as if it was made for it. That European style tacho appeared on a lot of upgraded road racers in the sixties. They are the nicest thing I've found at the wreckers in recent years. - look so authentic !

Yeah- thanks for posting that! It is a pretty handsome looking tach. If I understand correctly, it will work with the 1:1 reversing Smiths tach drive?

I believe you need a 2:1 drive on the timing gears, which run at half crankshaft speed. The tacho itself is 4:1. If you unscrew the gearbox on the back of the unit, and turn it over and replace the screws, you can set the tacho up t o suit the situation where the cable rotation is in the wrong direction. I bought my first unit about ten years ago when I saw it by chance at a wreckers in Melbourne (Australia) . I recognised instantly what it is copied from, and I was absolutely stoked to get it. It looks so right on my Seeley. The standard commando drive is correct for that head. My other bike's motor has an H1 Kawasaki bottom end, and I reversed the little gearbox on the unit for that. If you go t o any wreckers , you are likely to find one, nobody would use them on a modern bike, and the classic guys wouldn't know a bout them. You can probably even buy a complete new one with the mount. It would be interesting to know where Suzuki sourced them.
If you have a look at the photos that I've posted you can see the profile of the tear-shaped plate which is used t o mount the unit. If y oumaske the plate t o fit under one of the caps on top of your forks, that would be the way to go - a very easy exercise . It needs to stand up at least about 45 degrees to the horizontal.

I hope you get as much pleasure out of those schmick tachos as I did, the look so authentic !

All my riding in suburbia on an old single (not Norton) is under 3000 rpm. ?
Doesn't even show on this tacho.... !

Nobody said you had to actually use it in anger, but your Inter should be able to rev to 6,500 without dropping its guts ! I never thought that a tacho on a road bike was used for anything in particular. The unit that I've described looks right - isn't that the most important attribute ? You can look at the cost in the same terms as the tubes of pain relief gel that you buy to help control the stiff neck you get from looking at your reflection in the shop windows as you ride by.

Rohan said:

All my riding in suburbia on an old single (not Norton) is under 3000 rpm. ?
Doesn't even show on this tacho.... !

Click to expand...

So long as the rev limit isn't under 3000, it'd be ok.

I've often thought it would be great fun to have a steam roller race.