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I've got a '75 Honda CB750k. The oil drain plug under the bike has gotten stripped out. It stays in fine still, but leaks oil slowly. Is there any place I can get an oversize drain plug to fix this? I've looked all over and can find the exact same size but nothing slightly oversize.

You could try wrapping the threads with plumbers tape.

I would try the teflon plumber's tape, wrapped around a Fumoto valve. That way you only have to mess with it once! Liquid thread sealer MIGHT work, as well, but the problem is oil dripping down from the pan and contaimanating the material...

If possible, do it the "right" way: remove the oil pan, re-tap to a larger known size, reinstall oil pan with new gasket.

If it's leaking the threads are buggered, steel bolt too tight into aluminum; the aluminum will always lose. Teflon tape might help the leak but won't help the real problem, which is buggered aluminum threads. It is caused by overtightening.

The only right way to fix it is with a Heli-coil. It is a steel spring-like insert that goes into the aluminum, allows the bolt threads to have steel-on-steel contact and your problem is gone. It involves re-tapping the pan, and installing the heli-coil. You can get/order one for your bolt at a good auto parts store (napa etc). It comes as a kit with the proper tap and the heli-coil.

It's the only real good way to put a steel fastener into aluminum. Most race/aircraft applications use them from the factory to prevent this from happening.

Using teflon plumber's tape is risky as you might end up with a piece dislodging and plugging up an oil gallery.

The best fix is a heli-coil. Check with your mechanic. With a heli-coil you'll end up with stronger threads than original. Still, use a torque wrench in the future if possible and replace the crush washer at each oil change, this saves much wear on the threads.

Thanks for the info - I'll check out the heli-coil.

Have you tried making a rubber washer that goes onto the bolt snug to see if that would help? Just a thought.

SkullMan wrote:Have you tried making a rubber washer that goes onto the bolt snug to see if that would help? Just a thought.

The oil gets really really hot, so unless you've got rubber specifically designed for it, that'll just melt right off.