Big Bore Kit

Hi Josh: Maybe they work alright (aftermarket big bore kits) but as a Service manager at a Yamaha dealer for longer than it seems, I get suspicious about the usefulness of these big bore kits. In certain engines, the increase of the bore alone can achieve some substantial seat of the pants gains. Usually though, I would expect to see better results with a bigger displacement increase over multiple cylinders. I may be wrong here, but I think that a solid top end (oversize or not) coupled with a proven set up package is what you should be looking for on a streetable SR. Perform a leak down test on your unit to get a feel on the state of affairs of your engine as it is. Then you can decide if it is worth tearing down to spruce it up. As far as my unit goes, it has approx 39,000 km on it. I have no combustion build up and decent compression. I have added a freer flowing muffler to the stock header pipe. I have installed a K&N air filter. (The stock filter flows about the same as a shop rag!) I also re-jetted the carb. There may be better and more aggressive ways to set up an SR (cams, full exhaust systems etc...), however I have been riding motorcycles all my life and continue to return home after every ride with a grin on my face and the motorcycle is as reliable as ever. I can supply more detail as to the jetting etc... however sometimes it is better to work off of a general idea for your set up and jet to suit. (different mufflers, air filters etc... may require entirely different jetting set ups) Anyhow, anyone else may pipe in here at any time...
Talk to you soon,
G man