my qt50


i have a 1980 yamaha qt50,and i need help i bought a new needle valve for it and put it in but when i ride it it'll start moving really goood and get movin fast but all of a suddon it boggs way down some times stalls but then it some time after bogging it takes off again or stalls whats wrong? cause i need help.

Re: my qt50

First, is that the float needle valve and why did you need a new needle valve? Check the obvious: throttle cable moves freely in the casing (no kinks or corrosion), slide holding the needle moves smoothly within the carb body (must be clean and it sometimes helps to smear a little gas on the slide to help lubricate it) and carb must be clean internally paying particular attention to jet passages, Also, is the float clear of any obstructions which might prevent it from mving up and down freely?

Re: my qt50

the symptom sounds exactly like it's on the edge of running out of gas.. you wouldn't be the first person around here to dump some fuel in the tank and find that the problem mysteriously disappears.

other than that, turn the tank's fuel valve off, pull the fuel line off the carburetor and then drain about a cup of fuel into a container. Fuel flow should be a thick, steady stream.

Re: my qt50

i needed a new float needle valve because when i got the bike the needle valve had hardly no rubber on the end.

Re: my qt50

mikehailwood /

i needed a new float needle valve because when i got the bike it didn't run and i checked the needle valve and it had no rubber on the end.

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