sheamuz wrote:necessary to replace the crank seals when pulling down the bottom end or only when replacing the crank. How can you tell if they are in good condition.

They are so cheap, it would be silly to not replace them. You'll kick yourself later when you button things back up only to find the crank seals leak. That goes for any seal on a engine when you rebuild it. IMO

And like Andy said - nut off with gun is ok. Use a torque wrench when tightening. I would also recommend a new nut, just to be safe.
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Andre E. Benguerel
1996 Honda NSR250R
Daijiro Kato/Fortuna Replica #74

2000 Honda RS250R (NX5)
2008 Honda RS250R (NXA)
AFM Expert #430