Join Date: Apr 2002
Location: Long Island NY
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Dumb Universal M4-30 question
I am trying to check on my tachometer's reading, using a non-contacting optical tachometer. I attached a reflective spot to one point on the lower belt pulley, below and to the right of the water pump housing.
The reading I am getting is about 2X what my tachometer reads. So at idle the tach reads about 800 RPM and the optical device reads 1600 RPM.
I don't think my idle speed is that fast.
I realize I have no idea what is attached to this pulley, inside the engine. Is it the crankshaft? Or a camshaft that might be running at 2X the engine speed?
Added info: the pulley I am looking at with the optical tach has 3 flat "feet" each of which has a sturdy threaded hole in the flat part. Was this meant for a power take off in its previous life as a tractor engine before marinizing? If so, this must be the crankshaft?
Does anyone know? Is there a better place to stick a reflective spot?
Fluctuat nec mergitur
Last edited by pegasus1457; 07-04-2009 at 12:45 PM.
Reason: more info added