What do you consider to be big power?
The reality of high power NA bikes is they generally suck on the street. This is largely do to the fact that once you near the 240hp mark, the cams needed to support that power at rather large. In the typical cruising and low rpm range they tend to do what’s call cam surge. So when trying to sustain a constant rpm, the engine surges up and down a few hundred rpm making for a jerky ride.
With N.A. bikes making over 240hp the compression ratio is usually right on the edge of the limits of 93 pump gas. Catch a bad tank of fuel, and you could potentially run in to some costly repairs.
Nearing the 250 and up HP range and you’re talking about a substantial increase in displacement. A larger engine coupled with high compression and they tend to have a hard time staying cool specially in the southern states.
Also, on the topic of large displacement, you’re usually talking about a sizable increase in stroke. This causes two issues. One: the big end of the rods have much more extreme of an angle to them. This puts a lot more load on the rod bearing causing the bearing to wear much faster. This also makes stroker motors more susceptible to spinning rod bearings. If you’ve followed motorcycle forum for sale sections, or are on sales pages on Facebook, if someone’s selling a stroker crank, it’s usually under one of two circumstances. It’s a good deal because it has one or more spun rod journals, but can be repaired. Or it just came back from being repaired because it spun a rod bearing.
The other common problem with large stroker motors excessive wear to the thrust sides of the pistons. Because of the extreme rod angle and traveling so far down in the bore, the pistons tend to rock in bore.
Lastly, most of the stroker cranks on the market are re-welds unless you’re willing to drop some major coin on a billet crank. The camshafts also tend to be re-welds too. The welded portions are notorious for failing and causing expensive repairs. That why I insisted on using billet camshafts for my Warhead package that I install on some of my turbo builds.
IMO Making “big power” NA yeilds the lowest HP per dollar spent. Going off carpenter racing’s website $5300 will get you 230-240hp. The next step is the 265hp package for $12,000!!! Or you could spring for the 290hp package for $16,000. You’d have to absolutely hate money to spend that much for so little power in comparison to going turbo. Take one of my turbo kits for example. For less then $4k and a weekend in the garage you can bolt on 260hp on a stock motor on 93 pump gas. Buy a $45 can of e98, and jump the hp to 300hp just by pouring in fuel and switching the map.
But if that instant torque, is enough to make you refuse going turbo, I can always get you set up with a supercharger.
