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If anyone has a stock IN and EX valve guide handy, would you plz measure the overall length of each and post the numbers here? Either 256 or 447 is OK. However, if you have both 256 and 447 examples I'm also interested if they differ? Thanks in advance.

Carb settings can be really difficult to establish and the following info relates to a very hot 447 street engine (750, 10.8 c.r., Megacycle 30 cam, Lillie head, Jemco exhaust) using 34MM flatslides. This setup supports 69 RWHP at 8000 and has good street manners. 190 mains 25 pilots @1.5...

This bike belongs to my friend Tony in San Diego. It's all Shell - frame, glass, etc. - and performs as well as it looks. Suspension, brakes, etc. are all top of the line bits. Wheels are alloy 19" and roll on Maxxis flat track race rubber. The engine is a fresh 750 with all the mods...

I am rebuilding an early, pre-1975 256 series race engine and the crankshaft cam chain sprocket is in bad shape. Yamaha no longer "supports" this bit. The Yamaha part number is 2561154900. It is a press on sprocket and looks like a smaller version of the sprocket on the camshaft. If anyone...

I've had several people email me asking about what they should expect in terms of added flow in a ported vs. stock, unported head. I don't claim the modified head tested here is the best ever, but it is a very good one and provides a useful comparison for anyone looking for real numbers to...

Here's some great info for anyone contemplating building a long rod engine. This one uses CR500 rods, but Michael Morse suggests that the KX500 rods may also be suitable (with appropriate modifications, of course). Check it out. Craig The quest for the ultimate XS 750 dirt track engine...