Idles but won't throttle (SOMETIMES??) 04 Zuma

[ejlundberg]

So my YW50S is acting a bit funny..

It started a few months back (but I haven't had time to get into it until recently). On my way home, it died out, then when I got it started, it would bog down under throttle. Happened fairly quickly.

Now, I have changed the air filter, cleaned the entire carb, changed the spark plug, ran inspection on the petcock, and taken off the muffler to check for clog.

But HERE is the part that might mean something. It works sometimes? After I changed out the spark plug, it ran beautifully, seemingly faster than ever. I took it around for a test and about 7-8 blocks away, I stopped at a red light, and when I tried to throttle back up... nothing. Bogging down again.

Same thing happened when I took the muffler off. Initially, it was still bogging down.. then, 5 minutes later, I started it up again. This time it ran for a minute or so before I turned it off because its too loud for the city.

What is making my old Zuma behave like this?

P.S. I'm a newb.

[humanshield]

Unless you COMPLETELY drained the tank and used FRESHLY purchased gasoline from a good gas station, put into a verified clean and moisture free gasoline container....I would say water in the tank.

OR....

You have more junk in the fuel system (float bowl / jets) and it needs to be cleaned again.

[gsx600racer]

First, when you say you removed the muffler, did you remove the whole thing ?

If so you will destroy the piston and ruin the engine.

Second, +1 to what humanshield suggested.

[ejlundberg]

I've heard mixed reviews on damage from removing the muffler but it don't believe I could have caused any damage in the short amount of time that I tested it. This did happen when it started to get warm out in spring so possibly water from condensation in the tank that I didn't clean out. I'll swap out the gas tomorrow.

['O'Verse]

Either change out or add a fuel filter coming from your tank. Helps catch most of the bigger debris before it has a chance of entering the carb. Injector cleaner like sea foam won't hurt. Both Relatively cheap. Also give your reeds a look over

[AtariGuy]

Make sure the gas tank is clean and get fresh gas/oil. Then check fuel flow from the tank through the petcock, filter, and through the float valve in the carb. Ask me about that float valve some time...

Then make sure your carb/jets/etc is sparkling clean. If that don't help, start checking your spark. Let us know what you find

[ejlundberg]

(Exhaust pipe back on, changed the gas). Pulled the brand new spark plug. Was fouled.. another new one, turned it on and just tested it for a second, runs great. Too rich or air leak (or other)? What should I do next?