I bought a used 84 that already had that kit on it. The yamahopper had been knocked over onto its left side at some point in its past. When that happened it broke off the brass oil injection nipple going into the side of carb. Someone half ass rigged it and it was not staying put. I drilled out the broken stub still in the carb and managed to get what's left of nipple to press tightly back into carb. After that I surmised it would be smart to have a look at the cylinder. The kit has been soft seized (with lots of scoring) and still runs good. Hits 30-32 consistently with all else completely stock. Truth be known the broken injection nipple was probably the reason the kit was installed to begin with. Anyway I purchased a second identical kit and have yet to put it on. The kits are hit or miss. Some research found that there are porosity issues within the bore of some castings. All in all worth the money if you get a good one. Like Graham said, they are not bolt on and need cleaned up. (edited)