Big Bore vs. Stroker
Since the advent of the very affordable Hot Rods Stroker Cranks, I have gotten lots of questions, and read lots of thread titles, with the question of which was a better way to go: Big Bore vs Stroker.
The answer has been:
Within the amount of bore or stroke change we are talking about in these engines, you should pick whichever one you either want to replace, or need to replace. Because at these levels of change, it is merely a matter of ultimate displacement increase as to what the engine will perform like, as opposed to one changing your engine into a big bore/short stroke screamer, and the other into a long stroke stump pulling tractor.
At these levels, it is pretty much cc's of displacement change, and that's it. So it would be up to what someone either likes more, or has to change out of necessity.
The graph that follows is for comparison. They aren't apples to apples, but it's the best I've got to show.
The RED lines are from Venom’s TRX as a 477cc / 99mm bore setup (stock is 96mm).
The BLUE lines from Venom’s TRX right now as a 471cc stock bore 3mm stroker.
Included are the A/FR runs for clarity of what's going on in the bottom of the RPM band. I try to jet for an average A\FR between 13 & 14:1. The blue runs at 477cc are way too rich from the accelerator pump shot until the pump shot is burned off at around 7000 RPM. Once the air/fuel ratio comes up into good, so does the power curve. I didn't tune that out of the accelerator pump shot during my dyno testing because nailing the throttle in top gear, at low RPM, where the engine would take the longest to burn off a pump shot, isn't representative of how it works during actual riding conditions. Now, for comparison, I wish I had turned down the accelerator pump shot. As I said, not apples to apples, but close enough to compare a 3mm bore vs 3mm stroke comparison.
This should help some in making a decision.
Also, Venom doesn't recommend running ANY kind of a Stroker Crank unless you have it trued + welded + balanced to the weight of whatever piston you are running.