A few days ago I was revisiting a Motorcycle Classics magazine article from the July/Aug 2015 issue which featured Laf Young's restored 1986 VFR750F. In it, the author spoke to the transition to gear-driven cams for the 2d-gen Interceptor make-over.
"Driving camshafts by gear isn't without its own issues. Gear lash can make accurate valve timing more difficult, and timing gears are noisy. To get around the lash issue, Honda used a spring mounted "scissor" gear system — essentially two gears side-by-side and slightly offset — on the cam drive gears, offsetting the teeth by roughly half of the pitch. This allowed the lash to be entirely taken up by the tension of the two teeth resting together. The gear-driven cams went on to be a key feature of the later VFR750R."
I've just completed mechanical checks on Project 39, a '93 VFR750, which required removal of the cam gears in order to change the valve shims during the adjustment procedure. In the above photo, the removed cam gear is no longer under spring tension so the offset is clearly visible.
"Driving camshafts by gear isn't without its own issues. Gear lash can make accurate valve timing more difficult, and timing gears are noisy. To get around the lash issue, Honda used a spring mounted "scissor" gear system — essentially two gears side-by-side and slightly offset — on the cam drive gears, offsetting the teeth by roughly half of the pitch. This allowed the lash to be entirely taken up by the tension of the two teeth resting together. The gear-driven cams went on to be a key feature of the later VFR750R."
I've just completed mechanical checks on Project 39, a '93 VFR750, which required removal of the cam gears in order to change the valve shims during the adjustment procedure. In the above photo, the removed cam gear is no longer under spring tension so the offset is clearly visible.
(Right) Here, the cam gear is back in place and the scissor gears are back in alignment.
This is an example of yet another hidden bit of technology which make our VFRs a bit more special than the rest.
This is an example of yet another hidden bit of technology which make our VFRs a bit more special than the rest.
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