I don't often build the 750 with Wiseco pistons, mostly because their cost is high enough to scare off the potential owners. In years past, this cost was almost warranted. Today, I am not so sure.
Last Fall I was requested to build a Wiseco 836 for someone, and one of the rings in the kit came with a void in it: as soon as it was spread for installation, it broke in half. I had to buy a new set, then Wiseco was supposed to refund the cost after I sent back the failed ring. This added almost 2 weeks to the engine build, and I never got my $35 back, either.
In December I bought another Wiseco 836 kit for another build. After waiting for 5 weeks to get it bored at the machine shop, they discovered one of the pistons was undersized by almost .002" (!). I contacted them, sent it back with the dimensions of the other pistons in the set, and about 2 weeks and 4 days later got another piston. I took that one to the shop and it matched: they bored the engine and I got it back after 8 weeks (had to wait in line again). Today, I went to assemble this engine top end and: THERE IS NO OILING HOLES IN THE PISTON PIN BOSSES, on this replacement piston. How the $#@! can this be considered "quality"?
For a living, I design, build, and program machinery that inspects parts just like these with cameras, lasers, and all sorts of computerized gizmos. It is so commonplace now that I can't believe that a company like this one doesn't use this sort of tech to inspect things like voids in ring castings and (missing) drilled holes. I say this because if they did, these problems would not be happening: this machinery makes 100% inspections, 100% of the time, no errors, all day, every day.
I have used about a dozen of those "cheapie" 836 low-compression kits from Thailand (Cruzinimage on eBay) in the last couple of years. Every piston is within a few ten-thousandths of an inch from the others in every kit, and so far none have varied more than .0004" from any other among all of them. This is Honda-like piston quality. I think the same folks who make the superior pistons from Z1 Enterprises may also make these (Z1 pistons do have a better finish, though). This is indeed good value.
Wiseco: while they might make 4 HP more than the low-compression variety, stand ready to have to deal with this if you go that route.
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Update 7/3: I contacted Wiseco about getting another piston, and they told me to "run the piston the way it is, we don't put oil holes in for the wristpins now". WHAT!? Then I tried to explain how the other 3 pistons have oil holes: he responded with "Just mix them together, they will be fine." This is pure bovine excrement.
These people, at least this guy in their Customer Service Department, are off-the-wall. A non-oiled wristpin in a 10,000 RPM engine will seize in a matter of minutes. There is no other oil path into these pistons for the pin.
IMO: Avoid Wiseco...
