INSIDE LOOK / NEW 121ci VVT M8 Engine / TEAR DOWN
Master Tech Miller Master Tech Miller
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 Published On Oct 24, 2023

VVT being the well known change to the new 121ci from Harley-Davidson, but what else is new?
Well a new 4-5/8" Stroke Flywheel, new piston, new cylinder heads, new intake manifold & throttlebody, new larger fuel injectors, new cylinders, new breather system, new lighter counter balancer, new shift drum design & more!!!!

I was down in Sydney for some updated training on the Revolution-Max engine for the Pan-America & Sportster S line up however I took full advantage of being able to fully tear down & inspect the new 121ci M8 engine while I was there.

I am really excited for what the future holds for this engine! Tuning will be an a great learning curve & I can't wait to get involved with that.

I was able to cc the combustion chamber which came in at 86cc. That is 2cc less than the original M8 engine at 88cc.

I was pushed for time & couldn't get to measuring the complete specs of the cam. All I focused on was the intake valve (rear cylinder) & total lift (rear cylinder).
The cam specs I was able to measure with no oil pressure in the cam phaser (unofficially) were ;
.519" Lift
Intake valve opens 7 BTDC
Intake valve closes 2 ABDC

It must be noted that when we were doing the degree wheel inspections, that the cam phaser had no oil pressure so I can not be sure exactly where 0 is on the phaser as some of the valve spring seat pressure may have been advancing or retarding the cam when I was taking the measurements.
Once the official specs are published by H-D I will post them.

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