Thread: gear drive cam

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Without opening a can of worms as to the merits of gear/chain/belt drives, can someone explain why gear drives with two idlers have one gear larger than the other?

The crank turns twice to the cam's single revolution. Intake stroke is one crank revolution, exhaust stroke is another.

Hi 36. Thanks for the reply. I was unclear with my question. I was specifically referring to the idler gears.

Hi 36. I was unclear in my question. I specifically meant why are there two sized idler gears? The crank and cam gear sizing makes sense to me.

As per the Pete Jackson installation instructions:

“In normal operation, power is transmitted through the “POWER IDLER” gear (the bigger one) to the camshaft gear. The “REVERSE IDLER” (the smaller one) gear is rotating under no-load and must have sufficient clearance. The sole purpose of the “REVERSE IDLER” gear is to prevent the “POWER IDLER” gear from being disengaged whenever the crankshaft gear rotates backwards, as occurs each time the engine is switched off.”

And there you have it….

So then I guess there's no magic to it going smaller. They're probably just saving a few bucks of expensive gear steel by making it smaller. Thanks.

buy a good chain set like rollmaster many companys put there name on there timming sets there are about the best . i used many chain sets with big power builds and used belts drives i like the most if in the budget .i do not care much for the way the 4 gears set ups work or the transfer of harmonics they put threw the engine as a matter of fact the 4 stroke events can not be as smooth is many think the 3 gear setups like milodon and donovan sell is a better way then the free floating idler set up. if you have a thing about gears then 3 gear set up is a better way. with out knowing what your building or if any power adders it would be hard to tell you what i would use