Timing Light with Tac

jbennett77 · Oct 9, 2015

Will the tach on a digital timing light work on a two cylinder? Appreciate any help.

Mike M · Oct 9, 2015

I have an auto style tach dwell meter and have used it before. But I forget exactly what I had to do ? I think it involved using the 4 cyl. setting and either dividing it by 2 or multiplying it by 2 ? Or it was the 8cyl. setting you had to divide for a 4 cyl. so I had to divide more for a 2 cyl. ? Easy enough to check out on one you pretty much know is close to good.

Mark Aden · Oct 9, 2015

it will work fine, timing light reads off one plug wire and tach will read same no matter how many cyl engine its hooked to

Mike M · Oct 9, 2015

I was wondering about those timing light ones as I do not have one of those types.
But I think you could run into problems depending on what machine and ignition type it has. Some systems fire on compression and exhaust strokes and some only fire on compression. Might throw it off.

forty40 · Oct 9, 2015

(quoted from post at 13:01:41 10/09/15) I was wondering about those timing light ones as I do not have one of those types.
But I think you could run into problems depending on what machine and ignition type it has. Some systems fire on compression and exhaust strokes and some only fire on compression. Might throw it off.

Since the dist turns at crank speed and fires every revolution, I switch mine to two cycle and it seems to work OK.

Pete in MD · Oct 9, 2015

The dist./mag turns at 1/2 crankshaft speed.

jjvb · Oct 10, 2015

I used mine directly on my 620 and it worked fine.

forty40 · Oct 10, 2015

(quoted from post at 15:19:40 10/09/15)

(quoted from post at 13:01:41 10/09/15) I was wondering about those timing light ones as I do not have one of those types.
But I think you could run into problems depending on what machine and ignition type it has. Some systems fire on compression and exhaust strokes and some only fire on compression. Might throw it off.

Click to expand...

Since the dist turns at crank speed and fires every revolution, I switch mine to two cycle and it seems to work OK.

Whoops full speed internet disinformation. Dist is 1/2 speed only, I do put the tach on 2cycle

jbennett77 · Oct 10, 2015

Thanks for the help. Got one coming.

skip33652 · Oct 10, 2015

Pete, all the A B D G H tractors have a magneto that fires everytime piston goes to tdc. in other words turns the same speed as crankshaft. later distributors were driven off cam at 1/2 crankshaft speed . you can use any timing light but speed will be double and timing will be half.Paul

PushnFords · Oct 16, 2015

I've been having trouble with getting a consistent rpm reading on a 520. I have a digital multi meter that has an inductive pickup but the readings fluctuate a lot...I don't know if it is the solid core wires affecting it or not. So then I tried hooking the multi meter to the coil using the alligator clips...same issue. I also have an inductive digital tach (Smart Tach) that I use on small engines but it will only read sometimes then shuts off and I have to restart it. My automotive dwell/tach/volt meter won't read low enough to set the low idle.

I have no idea what the low idle is...none of the readings I did manage to get match the tractor's tach. I tried to get the high idle set pretty close to 1460 and I think that is more accurate. I'm interested to hear how yours works for you?

Timing Light with Tac

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