My 92 GS500 (which I believe sat for over a year before I picked it up) is finally running decently well at idle. Now I am having problems with the mid-range. If I give it light, even throttle in first gear, it will pull smoothly from about 2.5K to 4K rpm. It will not climb above 4k without more throttle. If I then roll on a bit more, it hesitates, then lurches forward between about 4K and 5.5K. If I go WOT, it gets a bit smoother above 6K, but still a bit lurchy.

If I give it medium throttle from the start, it pulls hard but is lurchy through the whole range above about 3k. WOT is similar. It hesitates, then jumps forward hard, then hesitates, then jumps, etc.

I am a noob with carbs, but from searching the site, it sounds like this is most likely a problem with the jet needle range. Currently the bike is bone stock, 100%. I have not played with the jetting, so I am assuming that this is stock. There are no washers under the jet needle seat. I rebuilt the carbs and cleaned thoroughly with carb cleaner and many passes through an ultrasonic cleaner. Float height is almost dead on. Spark plugs look perfect, PO claimed to have replaced and gapped them right before I picked it up, although I have not checked the gaps. PO also claimed to have checked and adjusted valve clearances within the last year he had it, although I have not checked them myself. I checked for vacuum leaks after the carb rebuild, did not find any. There is a slight oil leak from around the valve cover, very slight and did not affect idle when spraying with WD40. Diaphragms also looked good, and I will check again next time I have the tank off.

So, what are the expert opinions on this? I will put a go-pro on the tank and take a video of several pulls to show the problem.

stock air filter?

Quote from: HPP8140 on July 15, 2015, 10:22:09 AM
stock air filter?

Yup. I pulled it out and blasted it from the outside with compressed air the other day, didn't seem to do much, visually. I have not tried running it without the filter in a while, maybe I will try that.