xs11 79 special number 2 cyl is cold

[LenB]

Hey BigalG - learning about your experiences have been very valuable to me. We're experiencing some sustained hot temperatures up here (as are many locales) and my 80G recently got a bad case of the stumbles, missing and running like crap when it got hot. Slow stop/start city riding didn't help any. First thing coming to mind was some form of fuel starvation, but it didn't seem to be limited to a particular cylinder. So, off come the float bowls, and, while there was some fine rusty sediment, no larger chunks of crud were found. Am rebuilding the petcocks and installing in-line filters anyway. It appears to come down to the choice of plugs. Was running NGK BPR5-ES plugs (good setup for cooler spring/fall/evenings) which seem to be too hot for these conditions and swapped them out with NGK BPR6EIX Iridium units. Took the bike on a road test designed to recreate the previous problems and it ran nice and smooth, lotsa power and even idle. As these are cruel and unusual weather circumstances for this neck-of-the-woods, we'll see how it keeps running. May switch to cooler plugs yet (BPR7EIX) if necessary but so far, so good.

Update - Still dropping cylinders, regardless of operating temperature. Had a look in the tank and it didn't look good - lots of rust! New plugs were helpful but not the ultimate solution. Time for a proper tank flush - going to try the vinegar / Marvel Mystery Oil route. (electrolysis looks dangerous if not done properly) Also still rebuilding petcocks, installing in-line filters and cleaning the float bowls (again). Trying to avoid removing the carbs completely if I can help it.