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I was recently lucky enough to score a Yamaha 125 DT 1978 motorcycle for free off of Craigslist. It had been sitting in the barn for some time ( the last time it was registered was 2008.) and the guy didn't know too much about it as it was a project bike that he had taken on that he no longer have time for.

From all outward appearances it looks like it ran out of gas and was placed in the barn as all of the parts are there and it doesn't look like that it was torn into at all.

The back tire will not move and the chain is tighter than hell and I'm about to remove the back tire and see if maybe that has something to do with it.. (by being bound up too tightly.) I've tried to find videos and blogs about how/where to find out what is causing the engine to not turn over but I have been unable to locate anything that has been very direct or to the point that I could understand.

I'm mechanically inclined but being this is my first motorcycle I don't know where to start. ( any and all comments are welcome. I appreciate your time, effort and energy everybody, thank you!) :,)

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If the engine is siezed, I've had pretty good luck with removing the spark plug(s) and filling the cylinder with PB Blaster from a bulk can. (Not the spray; that would work too, but far too expensive.)

Keep refilling (funnel will help) and wait and wait and have a lot of patience.

If the situation is too far gone, a complete teardown and cylinder refinishing/new rings would be the only solution. Verify that the engine is truly siezed, as there could be a transmission problem as well exhibiting the same symptoms. But my guess on a bike that old and not used is that the rings have rusted to the cylinder walls.

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As Steve says, after sitting for that long it's likely that the engine will have siezed.

If it were me, with a project like that, I'd be tempted to completely strip down and rebuild the engine, and use it as a great opportunity to learn...

I'd suggest the following:

  • Remove the back wheel
  • Remove the chain. Leave it to soak in suitable oil for a while to free up the links
  • Remove the gearbox/transmission. Check whether that turns freely. You'll almost certainly need to change the clutch too...
  • Remove the engine, and investigate it's condition. Remove manifolds, plugs, etc, pour penetrating fluid down the plug holes (as per Steve's suggestion). Leave overnight, then try to turn it by hand using a breaker bar or long spanner.
  • If you still can't get it to turn, start to strip it down fully.
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