I thought I was running 37:1 in the Ruima, and had a brain fart of 640z in a gallon so I broke in, and ran at 74:1 for almost 800 miles till Batts smelled my fart. Most kits run at 50:1 as a standard mix ratio. Most tuners run at 37-38:1 cause of high rpm's. It's more about the bearings than the piston/Cyl.. The oil tends to fall out of the mix anyway settling in the lower case. It gets slung out like a centrifuge from the crank