OK, I just rebuilt my Hitachi on my EA82. It's really not bad. I took everything out and cleaned it, one thing at a time. Take 1 jet out at a time, clean it, spray carb cleaner through the holes, and when you replace the accelerator pump, DONT forget to put the little ball bearing (check valve) in!!!! I also replaced the O rings on the venturis, (sounds scary but really not) and I took out what I think was the idle solenoid, it was full of corrosion, cleaned, let dry and put back in carb. It runs like a whole new car! I also shortened my throttle return spring, it wasn't tight enough and would idle up when I took my foot off the throttle, or pushed in the clutch. I'd be happy to walk you through a rebuild, I think it will fix your issues...Oh, I also had a bad base gasket...