I like voiding warranty's, not that Ebay really has them
I should warn you that I am not an electronics specialist.
Got onto ebay and purchased the cheapest analogue rev counter I could find.
Then started to pull it apart, I very gingerly pulled off the face and removed 2 bolts off the back.
I used a small screw driver and spent about 15 mins slowly working around at the metal lens clamp from the back, so I would not damage it too much and I could re-use it.
And now here is the circuit board
The switch you see on there has 3 positions too choose between 4 cylinder, 6 & 8 four stroke engines.
Now the biggest problem is that a 2 stroke single cylinder fires once per revolution, a four stroke 4 cylinder fires twice per revolution, a 6 cylinder 4 stroke fires 3 times per revolution, and an 8 cylinder fire 4 times per revolution.
So on the 4 cylinder setting the rev gauge would only be reading half of what the engine its actually doing. the 6th and 8th would be worse
Below the switch you will see that there is 3 resistors, 1 each for each setting.
Now, my plan was to measure the OHM of each resistor, my theory is I could replace the resistor on the 4 cylinder setting (or the 6 or 8 would work) for either a higher OHM or lesser OHM, measure the others Ohms on 6 and 8 to decide if it needs to be higher or lower, then get a potentiometer/trim pot (adjustable resistor) that would be as close as possible as to what you need (the electronics store people should be able to push you in the right direction), if you choose the wrong one it will be extremely hard to tune.
now placing in the potentiometer is easy-ish, they have 3 legs to solder, but a resistor has 2, to fix this you joint the middle leg to any 1 of the outer outer legs, so it has 2.
Then you remove the resistor that you are using and replace it with the potentiometer.
BUT LUCKY ME, if you look in the picture, below the switch and below the resistors you will see there is a potentiometer already there, looks like the master potentiometer so to speak.
So what I did was wire the rev counter to my car (four cylinder four stroke), had the guage set on the 4 cylinder setting and adjusted the potentiometer so that the gauge read twice the rpm of the car guage, it was an educate guess that it would adjust the needle read out, but it did.
PLEASE CORRECT ME IF THE ABOVE IS WRONG, I would hate to send people on the wrong track.
I would like to say I know very little about electronics
Anyway the gauge in action
There is three main wires to make it function (just like most after market gauges) 1 wire goes to the 12v+ one 12v- and the last one goes on the black terminal on the coil.
And there is two other wires, that is just for the light.
Next thing for me to do, re-assemble with silicone to make it weather tight, and make a custom mount.
I may make a new face for it and re calibrate it to make more of a 12,000 RPM reader.
Could someone tell me what sort of revs to see out of these Dio engines? worked and standard...
all fun and games, thanks for watching
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