I've been posting for a couple of weeks on the QT50 I'm working on, so some of ya'll know the deal, not going to drag all the boring details in again. Tried pretty much all the suggestions from before and got some results. It cranks on the first try, idles smooth as silk and runs OK. Same problem, won't go past 20, starts bogging down. Was wondering though, and I need some input, I did swap carbs. out. I have a 1980 QT50 that I've been using for parts, that carb. was in pretty damn good shape. Somehow oil got in it when it sat for all those years and preserved pretty much everything. The 1983 QT50 that I'm rebuilding, its' carb. was totally trashed. All the gas inside it varnished, well, you get the picture. I pretty much put the 80 carb on the 83 one I'm rebuilding. Question: could that be my problem, wrong carb. set up? All pieces, I mean ALL, fit and interchange. In fact, I did use a part or two off of the 83 carb and put it on the 80 carb. From what I've researched, these two engines should be exact. Both are 49cc, both used Mikuni carbs, all threads, needles, bowls, etc. etc. are exact. Was wondering maybe, for EPA reasons, Yamaha made a suttle change in their design from 80 to 83? Did a plug chop, has a brand new plug, and it's dark. Too rich. Maybe I should put the 1983 main jet on with the 1980 carb? They are both identical. This 83 I'm working on has only 200 original miles, can't believe it would be something mechanical. I blew out the intake pipe with carb cleaner, no avail. One thing I did notice, when on the stand, breather off, wide open throttle, small amounts of gas droplets will come out of the air intake. Got a feeling the master is too big, just hard to believe because this is the original factory set up.
Anyway, thanks in advance for any input.