Using a timing light

[3or4wheels]

I'm trying to time an 83 R with a Snap-on MT1261A Timing light but using the tach function the rpm on the light is giving a very high reading.
Do I have to divide this reading by 2,4 or what's going on?Is this light compatable for a 2 stroke?
At best and between the fluctuations that the light gives out,it looks like the engine timing is slightly retarded with the stator timing marks aligned.
Is this normal for Honda to set the timing on the "safe side" ?
I have minimal instructions and experience with this light,so if anyone could explane me the features this thing has it would be greatly appreciated.

[El Camexican]

I suspect that that tool is for 4 strokes. What I do on my engines is set-up a degree wheel and indicator and set the indicator to TDC (mounting the wheel is the hard part, spacers, foot pegs, brake, etc.). Pull the plug wire and throw a spare plug in it. Turn the engine slowly by hand and note the location of the indicator when the plug sparks. Adjust as required. I doubt you have an advance function on that engine, so no worries there. However, if you have timing marks I would think that you can just use the spark method to set them to the marks. Good luck. (NOTE: Don't try to use a multimeter for this)

[wonderboy]

I think (key word being think) that you do need to divide by two.

The light triggers using the clamp around the plug wire, correct? Think if you were on a car engine, the plug only fires every other revolution of the crank (well, on most old cars anyway). On your R, you are firing on every revolution. The light is thinking that you are having two revs of the crank for every firing, so the RPMs it is reading out is double.

I think you have to do the same for some four strokes as well, depending on where the CDI gets triggered. On machines like the 350X, the CDI trigger is on the flywheel, which means it gets triggered on every revolution of the crank. What this gives you is just an extra spark at the top of the exhaust stroke, which doesn't do anything (for the engine) but it would give a double reading on a timing light tach that doesn't have a setting for 2 stroke.

As for the timing advance, the R and X CDI box takes care of that. It does advance the timing, but it does this elecronically, as opposed to some of the older machines (like a 200 Big Red) which has a CDI trigger run off the cam with a mechanical advance mechanism built into it.

[El Camexican]

I think (key word being think) that you do need to divide by two.

The light triggers using the clamp around the plug wire, correct? Think if you were on a car engine, the plug only fires every other revolution of the crank (well, on most old cars anyway). On your R, you are firing on every revolution. The light is thinking that you are having two revs of the crank for every firing, so the RPMs it is reading out is double.

What Frank says

[3or4wheels]

Tried again today but is was impossible to lower the revs to where the tach showed 2600 revs (2 x 1300 rpm for idle)
so I set what seemed to be a reasonable idle then increased the advance on the light by 1 or 2 degrees, which as
explained in some instructions I found,eliminated the fluctuations on the light and the timing marks then appeared to be
aligned.If this then means that the timing is 1 or 2 degrees retarded I'm not sure ??????

[El Camexican]

Tried again today but is was impossible to lower the revs to where the tach showed 2600 revs (2 x 1300 rpm for idle)
so I set what seemed to be a reasonable idle then increased the advance on the light by 1 or 2 degrees, which as
explained in some instructions I found,eliminated the fluctuations on the light and the timing marks then appeared to be
aligned.If this then means that the timing is 1 or 2 degrees retarded I'm not sure ??????

Any chance of you posting a video of this?