Vintage Dirt Bike Q & A

I have a mt125. I'll start it and run it for about a block or 2 then it will just quit. Has anyone experienced this, or know what it may be?

Not specific to the MT125 but it is a pretty common problem. Could be one of several things, dirty filters or sticky floats. I have had a couple of bikes do this when the air vent on the gas cap got plugged and it would pull a vacuum after it ran for a short time.

You can pretty much get a good idea of what the problem is by just carrying the right size wrench to remove the drain plug from the float bowl. When the engine quits just shut off the petcock, remove the plug and catch what gas comes out in a small cup. If it is dry, turn on the petcock and see how fast the gas comes out. If the flow of gas is slow, remove the gas cap and check flow again. If the flow of gas is still slow, you will have to remove the petcock bowl and petcock because there is a small filter INSIDE the tank.

Rick

Will,

I would ride it until it stopped, then immediately check for spark. It could be several things in the ignition if you are not getting spark. I don't know it that bike had points, or CDI. Either could need repair/replacement. The Japanese coils back the were slightly better than junk. A bad coil will often work fine until it gets hot, and will then malfunction. I have had this happen. I always check spark first, since it's easy to check.

If you have spark, then takes Rick's advice and move to the gas side of the equation.

Mark