Quote:
Originally Posted by greg737
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".
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That actually makes a lot of sense, thank you for sharing! The manual tensioner is on it's way and for giggles the next two YouTube videos I make will involve doing your own valve adjustment and how to remove and clean the OEM tensioner, both of which I didn't really find good conclusive videos on (the valve adjustment videos had either good valve adjustment instructions or good valve cover removal instructions, but not both in my opinion). I'll be sure to mention that fact when I do the tensioner video. That's good info to have and know.