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Old 08-05-2008, 12:50 PM   #1
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Default What's wrong

I have two questions,

I have a little honda 125 dirt bike. It is spewing blue smoke when I start it. Are the piston rings shot do you think? What do I need to do to fix them? Is it difficult and worth doing?

Next, when I pull the front brake it starts trying to turn the engine over like I am pushing the start button. What in the world? Where do I look to fix that?
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Old 08-05-2008, 01:15 PM   #2
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Do you get smoke all the time, or just on startup? Smoke on startup, as I recall, comes from worn valve guides -- the oil seeps into the cylinders when the bike is parked.

As for the brake issue, you need to check the lever to see if anything is hitting the start button when you pull in the lever. If not, take the switch housing apart and see if there is anything inside that is capable of moving the switch. Clean it all out and pack with dielectric grease.
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Old 08-05-2008, 01:53 PM   #3
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The starting when pulling-in the brake could also be a miswired brake, or a frayed/shorted wiring harness.

Good Luck.
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Old 08-05-2008, 02:02 PM   #4
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The smoking is likely caused by bad valves/guides and/or bad piston/rings. If the smoking goes away it likely just rings. If you have no experience on small engines it's probably more trouble than it's worth to fix. But replacing the piston/rings is not a difficult task. I did it years ago on my wife's CB125 while using one of those Clymer manuals.

As far as the electrical goes you probably have a wire somewhere that has worn off its insultation or is broken. These conditions can cause very strange effects. You should open up the handle grips and inspect the wiring for broken or frayed wires. A manual would have a wiring diagram to ease the task.

There are no easy internet answers for these sorts of problems. You have to be willing to roll your sleeves up or pay the $70 per hour shop time plus parts. You're looking at several hundred dollars to fix a bike worth hardly that.
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Old 08-05-2008, 04:18 PM   #5

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Get some JC Whitney "Piston Seal". I comes in toothpaste tubes, and if you squirt a whole buch down the sparkplug hole, it'll quit smoking. Worked on my '51 Nash Ambassador.
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