motorcycle repair question, any mechanics?

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eject911

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i have this yamaha 750, i think 1983, and i need an opinion on the starter

i do not have a battery for it, so i tried jumping it from my truck, but the motor does not turn fast enough, it seems that it turns harder past one cylinder then better over the other, then again barely turns over the first one. i thought it was the cables but...

then i borrowed one of those battery jumpers from my buddy, AND i had the jumper cables connected on my truck, and still exactly the same scenario, not even a little bit better.

i took both spark pugs out, and the engine turns fine that way, of course it does not have to make compression.

so can the starter just be "weak" like that?

thanks
 
Personally, I would first make sure it is a 12 volt ignition, and not 6 volt. Many of the older yamahas had 6 volt systems.

Secondly, the ignition will not run without a battery. Meaning, it is a closed loop system, so buying a new battery is the first step because it will not run when you remove the battery cable..

Third, it is unlikely that you have a weak starter. Starters typically fail when their primary or secondary winding fails... One thing to check the starter cable, and all grounding wires, however. Any one of these being bad will create the condition you are describing..

Finally, if you try a new batter and it still does not work, and this is a motorcycle that has been sitting for a while, my guess would be that is it increased piston friction. Meaning, replace the oil, pour a little down the cylinder, and turn it over a couple times without the spark plug. If that still does not fix the issue, then chances are you have a faulty set of rings on one of the pistons...

Good Luck and I Hope this Helps..
 
that or it just needs a battery which is cheap and can get just about anywhere try yahoo local type in motorcycle battery should get you a local place to buy one
 
Yes, the starter motor can be weak.
Remove the starter motor from the bike.
Hold the motor firmly in one hand.
Attach the (-) jumper to the body of the motor (where the mounting bolt holes are).
When you touch the (+) jumper to the terminal of the motor, it should spin with enough torque to want to jump out of your hand.
If it feels weak, replace it, or get it rebuilt at an electric motor repair shop (approx $150).
 
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