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greg737 · May 1st, 2015, 08:26 AM

I was told when I bought my EX-250 (back in 2007) that the cam chain tensioner has to work harder at some engine RPMs because of the engine's firing order (this info came from an aerospace engineer/math-nerd type).

The inline-2-cylinder, 180 degree crankshaft architecture of the EX-250 results in a "big-bang" engine: the two power pulses are only 180 degrees apart then there's nothing for the next 540 degrees of engine rotation. At low RPMs this really yanks the cam chain around a lot.

Like the OP in this thread noticed, the cam chain tensioner has to work really hard down at idle RPM to about 2.5k RPM to counteract the cam chain "lash" induced by the big-bang nature of this engine.

In the higher RPM range the cam chain tensioner doesn't get worked as hard because the inertia of the cam chain itself dampens out the "lash".

May 1st, 2015, 08:26 AM	#27
greg737 - Name: - Location: - Join Date: May 2009 Motorcycle(s): - Posts: A lot.	I was told when I bought my EX-250 (back in 2007) that the cam chain tensioner has to work harder at some engine RPMs because of the engine's firing order (this info came from an aerospace engineer/math-nerd type). The inline-2-cylinder, 180 degree crankshaft architecture of the EX-250 results in a "big-bang" engine: the two power pulses are only 180 degrees apart then there's nothing for the next 540 degrees of engine rotation. At low RPMs this really yanks the cam chain around a lot. Like the OP in this thread noticed, the cam chain tensioner has to work really hard down at idle RPM to about 2.5k RPM to counteract the cam chain "lash" induced by the big-bang nature of this engine. In the higher RPM range the cam chain tensioner doesn't get worked as hard because the inertia of the cam chain itself dampens out the "lash".