We had these made just over a year ago! These run on 87-93 octane! Regular pump gas. 10-5-1 comp, the stock is 9-8-1 a little extra compression with this kit. Bolt-on ready. No modifications are required! (Please check out our other listing for other Honda ATC Models! Atc200 atc200e and atc200es ) Pre-bored and honed to 63.00mm Comes with every seal and gasket to rebuild your top end! We have been running one of these on a atc185s 3 wheeler for over 1 year now! hard! No issues! We recommend a certified mechanic to do your rebuild!! These will fit the atc185s 1981 1982 and 1983 also the Honda atc200s 1983 1984 1985 1986. THESE ARE THE CORRECT CYLINDERS!. NO HOLE FOR CAM CHAIN ADJUSTER! (Look at last photo) Don't be fooled by other sellers. These are brand new and first listed Here on ebay! . Honda ATC 185s 200s Cylinder And Piston New with gaskets!