Yamaha QT 50 won't start!

unclejack857 · Posted: Sat Aug 09, 2008 6:09 pm Post subject: Yamaha QT 50 won't start!

Hello, I have a 1980 Yamaha QT 50 2 stroke moped that I can't get started unless I use ether. It is getting gas via the gas line from the petcock and it has really good spark. I can get it to run with ether but it immediately goes WOT! I started it with ether and sprayed ether on and around the intake and carb and it only changed the rpms just a little. I originally tore the carb apart to clean it after it just quit while I was riding it. Know it won't start at all! Crying or Very sad

Any ideas? Thanks! Jack

jayel · Posted: Sun Aug 10, 2008 6:19 am Post subject:

using ether is really hard on a engine washes the cylinder wall down, if you have fuel and spark and the timing didn't change that leaves compression you probably need a new set of rings

unclejack857 · Posted: Mon Aug 11, 2008 9:05 am Post subject:

Compression seems good but I don't have a tester. I have 2 QT 50s and I held my thumb over the plug holes on both. Felt good on both. Is their any adjustments I may have made to the carb. that would keep it from starting? I did adjust the clip on the needle a couple notches. Thanks, Jack

unclejack857 · Posted: Mon Aug 11, 2008 1:15 pm Post subject:

I did do a compression test. I borrowed my brother's tester. If I used it correctly both my QT 50s have the same amount of compression. One runs very good and the other won't start! Any ideas from anyone? Thanks as always! Jack

jayel · Posted: Mon Aug 11, 2008 1:21 pm Post subject:

put the clip back in the middle and put in a new spark plug, air mix screw in to touch and then out 1&1/2 turn

unclejack857 · Posted: Mon Aug 11, 2008 2:09 pm Post subject:

I switched my carbs. I put the good running bike's carb. on my not running bike to see what happened. Same thing! Won't start unless I use carb. cleaner. It then goes WOT, but I'm guessing that's due to the carb. cleaner? I'm baffled once again! I would almost think somehow it's not getting fuel to the cylinder? I checked the sparkplug and it doesn't seem to be wet at all!? I know I got fuel to the carb. Any ideas? Thanks as always! Jack Crying or Very sad

unclejack857 · Posted: Thu Aug 14, 2008 7:07 am Post subject:

Fixed it! (lol) I had a very small metal burr on the inside of the carb. body that was causing the slide to stick! I got smart and had a friend of mine work the throttle while I watched the slide. Wasn't moving! So, I sanded the burr and problem fixed! Runs great now after my 10 carb. cleanings! (that's originally what I thought it was) Anyway, runs great, for now, anyways!! Jack bike