dmplatt said:
That is one nice looking bike. Great job.
Can anyone tell me how to check the voltages to the tach. And also, do you HAVE to have a scope to check the signal from the coils?
In addition, which wires are which?
It's strange that the signal works fine upto about 5 or 6k, then goes to heck. Maybe it's the TYPE of capacitor? Is there a resistor type filter I can put on the wire to filter the noise?
Thanks
Dave
Hi Dave,
Thanks.
I understand that you are trying to fix this, because Suzuki-tachos doesn't come cheep.8O buying a used one makes now sense either because they have often the same problem.....
If you want to check electrical signals you must have SOMETHING to measure with, it doesn't absolutely have to be an oscilloscope.
You could have borrowed mine, but it's a far way to Tampa..... :roll:
One way is to connect another tacho (an instrument with tacho-function or just another tacho) that you know is working and see if it works on your bike.
If the bike is running as it should, the signal itself is probably OK down at the ignition coil, and otherwise the bike wouldn't run. The problem with the signal could more likely be that it is distored by something on the way up to the tacho.
The tacho has a 12V supply, you can measure the voltage with a multimeter, connect it as close to the tachoboard as possible. Fasten the multimeter on the bike, take it for a spin, so you don't have to rev it up on the driveway and take the readings.
I don't have a wiring diagram for the 750, but the signal wire is connected to one of the coils.
You could also build your own new tachoboard if you know that the tachometer itself is OK.
There is the possibility that the tachometer itself has a bad connection or that the instrument coil is damaged somehow, and the vibrations are causing the bouncing...?
i.e.
http://cache.national.com/ds/LM/LM2907.pdf Look at page 10
the chip is about $3 and mayby you can use the old circuitboard?
or
as I wrote before, you can change parts by chance, the tacho board has not much parts, a couple of resistors, two electrolyte capacitors, two thantal capacitors, one diode and a special IC marked ND SM014.
Check the board for cracks as well.
I could not found the special IC anywhere and it probably contains some OP-Amplifiers, it could be that this IC was destroyed on my first tacho.
It should be possible to mount an extra filter on the tacho input, but I don't know where to get them, check with your local electronic dealer.
I wish you Good Luck, I know this can be very tiring and frustreting to find what is wrong, remember the days two years ago, but as the tacho finally worked it was woth it!
