speed problems

i have a qt50 1979 and i replaced the jet for more speed so i upsized it to a #75 jet. But instead of gaining speed i lost speed. Some one told me to mess with the air/fuel screw but i don’t want to mess it up can someone give me more info on the air/fuel screw and tell me how to ajust it to the right setting? THax

Re: speed problems

you can't cure problems caused by a jet that's too big by turning some screws.. nothing regulates fuel flow at wide open throttle except the main jet size. If your air intake is wide open and the mixture is still rich you need a smaller main jet.

power is where there's barely enough fuel.. you gotta run almost too lean. Extra fuel cools everything down, slows combustion and wastes fuel and can cause misfires.

People are afraid of overheating their engines and tend to use and recommend jets that are way too big. This drowns the engine in fuel and kills power, but it's safe from overheating. Chances are you need a main jet that is smaller than any jet that anyone around here will recommend.

There's only one way to tune your bike.. to get carburation and ignition timing correct. You have to study and understand what's going on inside the average two-stroke engine and then learn to do plug chops and to properly read spark plugs. Taking other people's advice is easy.. but it has strict limits when it comes to tuning your bike.

Re: speed problems

well what size do u recomend i get for my qt50

Re: speed problems

i wouldn't even try to recommend a jet .. unless maybe if you weigh the same as me, we have the same bike and they have the same milage, with the same gearing, same exhaust system and port timing, we ride the same roads in the same climate and at the same altitude.. and your idea of performance is the same as mine..

I'd rather guess your shoe size .. hmm.. lets see.. Go buy some 10 1/2 D's .. i think they will fit perfect :)

Re: speed problems

your funny ahaha

Re: speed problems

George Smith /

id go back to the stock jet and see what it does if ya need more fuel go more if you need less go less......but stock is always a good place to start :P

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