I joined mostly to solve this problem! 2 stroke Yamaha QT 50

unclejack857

Ok, I am in the Vintage Japanese Motorcycle Yahoo Group and I was referred here by one of your members. I recently purchased 2 1980 Yamaha QT 50 2 stroke mopeds. I was riding one of them and for some unknown reason it just quit. I pushed it home and proceeded to check spark and fuel flow. Checked out. I then took of the carb. and cleaned it. Put the carb. back on and now all it wants to do is go WOT (Wide Open Throttle) I have cleaned and tore this carb. apart at least 10 times. I even took off the carb. off the other moped and EVERYTHING looked exactly the same! Only thing I did on the WOT moped was change the clip setting for the needle valve. I finally got frustrated after probably 15 hours of messing around and I switched the carb. from the WOT moped to the non WOT moped that runs good. When I did this it still went straight to WOT!, even with the carb off of the good running moped! I then put the WOT carb on the other moped and it is doing the same thing! I now have 2 mopeds that will start on the first kick but go immediately to WOT! When I put the original carb. back on the original moped that runs good, it runs good! I hope this all makes sense as I know it long and probably confusing, so ask questions if need be! I'd pay good money to know what's wrong! Thanks in advance !! Jack

jayel · Posted: Tue Aug 05, 2008 5:22 pm Post subject:

sound like you have the slide hooked up wrong check this site http://www.mopedriders.org/viewforum.php?f=2
lots of info on the QT's and manuals in the repair section btw I also have a 1980 Qt good little scooter

unclejack857 · Posted: Tue Aug 05, 2008 9:04 pm Post subject:

Thanks, but I believe I have it right, but who knows!!?? As far as I know their is only one way for the slide to go in for the throttle to move the slide freely up and down. I believe I have the notches lined up correctly. I was talking to a guy today that seemed pretty sure that I have an air leak somewhere. So, I guess I'm going to try that route next! Thanks! Jack

Steve Searles · Posted: Wed Aug 06, 2008 7:06 am Post subject:

I would have to look at it but.... maybe the cable end is not seating properly up into the slide. Surely you have the clip that goes over the needle before you put the spring in. That holds the needle down. It is something simple if both bikes are doing it. I have done 100's of QT-50 carbs.

unclejack857 · Posted: Thu Aug 07, 2008 6:04 pm Post subject:

Thanks Steve, I went out today and put the original carb. back on the bike that originally wasn't going WOT. It runs and idles good. The other bike still immediately goes WOT as soon as it's started. The clip and spring look like they are the same as the bike that's running good! I THINK the cable is seating properly in the slide. Any way I could tell? I don't think the slide is sticking at all as the throttle moves back and fourth smoothly at the throttle handgrip. Although, their is a very small bur I noticed on the side of the slide. Probably due to me putting it in their wrong the first time and having to work at getting it out! Any help is greatly appreciated as always!!!!!!! Thanks again!! Jack Confused