Tweet
I previously stated that I had bought a spare cylinder block from Andreas for use as a proto-type to determine how big a bore the XS block would accomodate and still be streetable. I have removed the stock sleeves and the bare block is on the way to Advanced sleeves in Ohio for machining and installation of 3.275 O.D. sleeves that will accomodate 78 mm pistons which will fetch 1311cc's. This bore size will still leave a wall thickness of .102 which is ample for a street bike. With this sleeve you could go to a 79 mm bore but that would leave the sleeves at only .0825 thick, too thin for me. You could (might) go to the next larger sleeve which has an O.D. of 3.42 however with that one you would be unable to use the stock "O" rings at the bottom of the sleeves which could cause an oil control problem in a street bike. The 3.42 sleeve would also require a case clean up which requires disassembly of the bottom end and I don't want to go through that again, at least not now. In a drag race only application the 3.42 sleeve would work but for a street bike it would ultimately seep/weep oil. For my application, the 3.275 O.D. sleeve will work out nicely. Last winter as some of you know I put a Wiseco 1179 kit in my Special and wish now I had gone the after market sleeve route but at time I had been told that the XS block would not accomodate larger replacement sleeves however that information was bogus. I had also been told by Yamaha tech in California and by the Yamaha dealer in St. Louis that the stock sleeves could only be removed by boring them out but that was also bogus as 45 minutes in an oven @ 450 degrees was all it took for them to slide out on their own just like my old FJ. Of course a 78 mm bore requires custom pistons and a one off head gasket but Wiseco, J&E and some others will make anything you want. I'm actually more than a little surprised that the stock XS block will accomodate these larger sleeves because of all the misinformation I have gotten regarding this modification however I shouldn't be as the XS was over engineered form the git go. The most diffulcult part of this whole deal will be making myself a base gasket but then again I might be able to trim up a stock one to make it fit, I can only hope. Thirteen hundred and eleven cc's, sounds good to me.
And folks can get the required head gasket and new rings from Cometic/Wiseco as needed. You would be the one to tell whether it's okay to use the wrist pins that come with the kit vs. getting new ones?? Looking forward to seeing the finalized project, and a list of any other mods added to this, like cams and such!?
Comment