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How to determine if motor work was done?

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I'm buying an XR400, current owner claims the previous owner had the motor bored along with a few other things.

Obviously the only positive way to confirm this without having documents is to take the motor apart. Are there other tell tale signs that would indicate that the motor has at least been apart?

Wear on fasteners?

Marks on the cases or jug from being clamped on a machine for boring?

If the bike runs good, maybe I could use the type of exhaust(XRs Only slip on) and jetting (Yamaha pumper carb) to determine the motor size based on previously documented conversions?

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Best thing is wear on fasteners and aftermarket gaskets. Second best would be the current jetting, but that is a hit and miss. Some shops will sometimes mark the engine as their work, but rarely.

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Should be obvious signs of new head and base gaskets if the engine has been tore down recently. As for the bore job. Is it a .010" or 0.20" oversize job to clean up a worn cylinder or a displacement increase bore job? The clean up bore job will yield very little displacement thus power increase.

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Realistically speaking, unless the PO can show receipts, you have only his word until such time as it might be necessary to get inside the engine.

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Realistically speaking, unless the PO can show receipts, you have only his word until such time as it might be necessary to get inside the engine.

That's what I'm thinking. The guy I'm buying from did not have the work done. The person he bought the bike from did. I have no reason to doubt the guy, he was very straightforward and honest throughout, and everything else he told me about the bike so far jives with condition.

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