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1972 Yamaha 125 AT1


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I just picked up a Yamaha 125 AT1. I need some info on it. It has no spark just want to know where to start. Its in good shape for the year and every thing seems to be there. I don't know to much about the older bike. This might be a dumb question but does the battery have to have a charge for it to get spark. And is this bike worth anything

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well I got it to run but it reved out so I shut it down. I noticed that the slide in the carb is not moving freely. When you open it all the way it will not come back down. I cleaned it up and it is still sticking at the top and will not come back down. what would make it do this. I also would like to know what is the meaning of a torque induction and what would the mix be if I just premix it. I would appreciate any info on this bike not to familiar with the old two smokers

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Clean the carb again and check that the throttle cable is smooth and free. If the slide is sticking that should be an easy fix. Torque induction was the reed valve for that year I think. Don't premix unless you remove or disconnect the pump. I'd leave it alone, the oil injection was pretty reliable.

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"Torque Induction" was the term Yamaha used for reed valve induction at the time. Most 2 strokes had the intake controlled by the piston skirt in the early '70's, so reed valves were an innovation that allowed the bike to retain good torque characteristics, while still allowing decent top end power. It wasn't long before all 2 stroke dirt bikes had reed valves.

As far as your slide sticking - are you sure the needle is falling into the needle jet when you slide it together? Maybe check you're slide for dents ... :banana:?

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