I had just read that John Underwood (xsjohn) was killed in a tragic car accident several days ago during a heavy rain storm. He was in a head-on collision with an SUV.
For those who don’t know of XSJohn, he designed and made adjustable needles for the BS34 Carburetors found on 1980+ xs650s. If you have worked with these carbs, you’ll find them very limited in adjustment/jetting compared to the BS38s. His expertise in these carbs have brought them up to be great performers, especially with exhaust and air filter modifications.
His ad on eBay claims major increase in performance, smoothness, torque and starting. Lowers head and cylinder temperatures 20 degrees and vastly improves performance and cruising smoothness. Better balanced cylinder temperatures with custom turned needles for each cylinder. Mileage 49-53.
Personally, I’m not sure of all these claims, but I do believe in them. After an exhaust mod on my 1980 xs650SG, I could not get the jetting right. So I ordered a set of his needles. Before he sent them to me he emailed me asking for details on my setup. Satisfaction was his goal over profit. He gave me great advice and with his needles I got my bike running great. This was about a month ago.
John was very passionate about the XS650 and will be missed by many.
Mike (aka grepper)