Fitting -ve digital tacho to +ve electronic ignition.

[muskrat]

G'day all.
I didn't know if this would work but I gave it a go. I wanted to see what RPM the 51 A7 was doing at 60MPH, I could have done the maths with the gear ratios but that's no challenge for an electrickery dunce. I got a cheap Chinese unit off ebay   http://www.ebay.com.au/itm/Universal-Waterproof-Motorcycle-LED-Digital-Tachometer-Speedometer-Tacho-Gauge-/380999078077?pt=AU_Motorcycle_Parts_Accessories&hash=item58b55090bd
and as usual no instructions. So using a spare battery I found red = positive, Black = negative so that left green as the trigger. I wired red to an earth in the h/light shell, black to the ammeter and ran the green down to the coil (duel plug lead type). Started her up and touched the green to one side, nothing, then the other side and got a reading so that is the - side of the coil which takes the black box signal. Hooray I now know she idles at 750-800RPM. And I didn't blow a single fuse! Can't road test as I snapped the clutch cable on Sunday.

[RichardL]

Muskrat,

That is cool for pennies. I guess it helps that your bike is 12V and electronic ignition. Sooo, did you happen to notice that the color coding of the wires is in the item description? Also, if red was negative I would think it was a manufacturing error.

I wonder if it works with, what do you call it, "sacrificial spark" ignitions, where both cylinders fire every time?

Richard L.

[muskrat]

G'day Richard. You have to forget about which one is earth, just go with the + or -. On our bikes - is power and + is earth. The unit needed + in the red wire and - in the black.. So I suppose the power is doing a figure 8.
Cheers

[duTch]

   You lost me at 'dunce'..but I kicked back in at 'don't need clutch for road test'.......

 I thought a clutch was only needed at standstill-test...??


           

[muskrat]

The clutch comes in handy getting up my driveway. Everything has to work to leave my shed.
Cheers

[olev]

Richard has a point about wasted spark ignition.
A four stroke would have to multiply the sparks by 2 to get the proper revs.
Musky, does the A7 spark in both cylinders together?
If it does I'll fit one to my 2 stroke single.
hope the back is coming along ok.
cheers
 

[muskrat]

G'day olev. Yes mate both plugs fire every rev.
Never weller.
Cheers.

[Angus]

Yes, for some reason I wanted to know what the tickover was and the speed in gears so bought one of these
http://www.ebay.co.uk/itm/Spark-Plugs-Engine-Digital-Tach-Hour-Meter-Tachometer-Gauge-Motorcycle-Boat-ATV-/291083825562?pt=UK_Motorcycle_Parts_13&hash=item43c5f2b19a
It seam to bit slow to catch up but worked 'Ok'
so
A7 tickover750-800rpm (snap Muskrat), can not recall the RPM in gears but I had been taking it very easy until then
A10 tickover 900-1000 could not get it to slow down without stalling, could be the suspected mag problem that will be fixed this winter

[Greybeard]

...Everything has to work to leave my shed.

Great picture! Love the mail box.

[muskrat]

G'day all.
Just did it's first highway run. Standard gearing sprockets at 60mph she was reading 3850rpm. I wasn't far out with my original guestamate of 4000.
Now that it's satisfied my curiosity I'll leave the wiring on the bike (quick connector) as it's good for tune ups, it'll live on my A65.
Cheers

[beezermacc]

On the subject of digital clocks, now that chronometric clocks cost as much as a house in London, I've been playing with clocks too. I found the digital speedo superb as it can be calibrated very accurately after removing the original speedo cable from the gearbox and fitting an electronic cable instead, on the gearbox, not the front wheel where (IMO) they always look a bit tacky.
http://www.a7a10.net/forum/index.php?topic=8867.0 Not had as much luck with the tacho which is a bit random as I'm still using a magneto. Just bought the tacho as used by Musky for £9.99 off ebay and may experiment with this and a coil / disi conversion which I've used before.

[bsa-bill]

removing the original speedo cable from the gearbox and fitting an electronic cable instead, on the gearbox,

HI beezermac I bought the Tacho as  I have Pazon ignition so worth a gamble at the price, a matching speedo would be nice tho so I'm wondering how you worked the pickup from the gearbox, any chance of a pic please.

And while I'm on me knees begging, any chance of any of you putting up a pic or two of the tacho wiring and where you took the signal from. ( took a screen snip of the advert for the wiring and forgot to save it from clipboard to file, PC seems to save to cloud unless you intervene, would have a look in that cloud someday but frightened I  get struck by lightening from a big finger  )

[muskrat]

G'day Bill. The green trigger wire goes to the - side of the coil for +ve, the same side as the wire from the black box top photo.
There are types that use a wire wound around the spark plug lead to get the signal, should work with a magy.
Cheers

[beezermacc]

Hi Bsa - Bill. The cable is supplied by digital speedos. http://www.digital-speedos.co.uk/bsa--triumph-cable-drive-adapter-1123-p.asp. It just fits onto the gearbox in the same way the speedo cable would normally fit. Presumably it works in the same way as a magnetic pickup on the front wheel. The speedo comes with instructions for the front wheel magnetic system but you just substitute the gearbox cable instead and calibrate the speedo as though it had 16 magnets on the front wheel. I tried using the front wheel magnetic system but it was cr4p! However, the substitute gearbox cable is excellent.

[bsa-bill]

Cheers beezermac - think I'll need to talk to Santa, might get a good price for the Smiths unit I use tho.
Cheers Muskrat too