another question on the tach/calibration...?

Question

on the tach/dwell/voltmeter(sears model no.161.216500) it says ":for 4 cyl.engine double 8 cyl scale": could i just multiply by 16 on the 8 cyl scale to get a single cyl reading? im just using it to check my timming at idle and full advance on my xl 600r

Answer 1

This is an interesting question. Those meters were designed back with the old distributor and points systems, and I believe were hooked to the coil. So, with a V8 the meter probably counted 8 pulses and knew the engine had turned twice. With a 4 cylinder it counted 4 pulses for two turns, therefore the reading would only be half as high, so, with a 4 cylinder you double the 8 cylinder scale. Your Honda bike is triggered from the crankshaft every rotation not from a cam driven distributor (1/2 crank speed), so, like a 4 cylinder car every 4 pulses will equal two turns. Therefore, unless I am mistaken, you can read your bikes RPM by doubling the 8 cylinder scale. Try it and see if it seems acurate, normal bike idle is approx. 1200 rpm.

EDIT: I made a mistake, on your bike 2 pulses equals two turns, so, you should multiply the 8 cylinder scale by 4 , that should work, uummm... I am not responsible for any death or injury incurred during your experiment.

Answer 2

geo46er...You're making my head spin with all those calculations LOL

inquiring mind...Your previous question, I thought you just wanted to hook up a tach.
But since you're just checking the timing, you don't need a tach.
A dwell meter just reads how long the points are open and calculates the point gap. In other words, a dwell meter is used to adjust the point gap, not the timing (and that bike doesn't have points).
The timing is checked / adjusted with a timing light.
Idle is slow RPMs, you don't need a tach to measure that.
Full advance is high RPMs, the advancer on motorcycles is usually full, at 1/3 of the RPM range.
Just rev the motor and check the timing with a timing light.

Answer 3

Multiply by 8.