Hi all,
I bought a hardline tach for tuning purposes and wrapped the pickup around the plug wire...
It is idling at about 1200 rpms which seems pretty good...I know that you can go down to around 1000 but that seems really low sound wise...

Anyway the tach can be set for 1 single pulse per rev (2-stroke), 1 pulse per 2 revs or 2 pulses per 1 rev...

I currently have it set for 1 pulse per rev and it seems right but I remember hearing we have a wasted spark on our bikes...

If I set it at the other 2 settings it seems to double my revs....what do you guys think?
Thanks!

Our 4 stroke engine only fires every other stoke.....and it only needs a spark once every two revolutions - but that would require having the spark controlled by the camshaft.  In the old days that is how they used to do it.....have the points working off the end of the camshaft.

In this modern age they just use the crankshaft to drive an electric pulse (without points) on each revolution....and the extra spark occurs just as the exhaust valves are closing in preparation for the next intake stroke, and the extra spark does nothing.  This is not only common on motorcycles.....cars and lawn mowers do it as well.

Yep....the tach needs to be set for a spark every revolution....just as it would be if the engine was a 2 stroke.  

Bubba wrote on 12/20/13 at 09:01:00:

Then he musta' explained it wrong... ...