Modifying tach signal?
 

I'm having a hard time finding a tach that will work with the twin in my bike. I know Shindy makes a nice electronic tach but are a bit pricey. The only other tach besides the crusty Drag Specialties mini tach will work but only read up to 8k is a Apexi tach. This is HMT so I can't see spending 2-300 dollars for a tach. My question is there anyway I could reduce the signal the tach is seeing by half since tach like Autometer and whatnot usually only at four cylinders and go up from there. Could I install resistor between the wiring from the tach to the coil? I mean what is on the inside of a aftermarket tach that adjust the signal from when you switch from 4 to 6 or 8 cylinder?

Re: Modifying tach signal?
 

sorry dad

Re: Modifying tach signal?
 

She can adjust my signal any day. Hell i'm redlining just looking at her. 8)

Re: Modifying tach signal?
 

Use a frequency divider latch type circuit.

http://www.electronics-tutorials.ws/...r/count_1.html

Takes pulses in and gives half the pulses out.

Re: Modifying tach signal?
 

so this could also be used on a 2 stroke? i really want a tach for my scooter, but i dont want to spend a ---- load on it either.

Re: Modifying tach signal?
 

Yep, you could filter down the signal from the engine, and shape it up into a square wave for the flip flop. One it's a square wave of the proper voltage (logic levels are 0 to 5vdc), you can do just about anything with it. As long as you find a tach that can read that same square wave, you are good to go. Even if the tach has to have a larger signal, you can amplify the square wave

Craig

Re: Modifying tach signal?
 

if you set input on 4cyl with a tach redline of 8k, a single cyl 2-stroke could fire 16k rpm and register as a 4cyl spinning 8k

same with super duper rev happy cars. 4cyl that revs 12k+ set to 8 cyl on tach and it reads 14k as 7k on the 8cyl setting

Re: Modifying tach signal?
 

My electronic skills kicked the bucket after I left the air force nearly ten years ago. Can you actually buy one or do you have to build it? The schematic almost looks like a relay type circuit with the four ternimals it would have. Enlighten us Craig on where we would find a frequency divider latch type circuit.

Re: Modifying tach signal?
 

just get and ebay tach they always advratise 1,2,3,4,6,8 cyc engine's it works on them all

Re: Modifying tach signal?
 

i just want one of my cheap CDM tach's to work on my CDM scooter. the most RPM it will ever see should be about 12k and thats a ways down the road. stock is about 8.5-9k.

someone help a nog out, i can solder things together, but i really know nothing about how they work