GS750 oil pan plug sizes

[Scudder]

Got an 1978 gs750 oil pan plug off ebay. Much to my surprise the plug from my old pan is too small for this new pan. Does anyone have any ideas on this? Did some 1978's have a larger diameter plug?

Scudder

[blowerbike]

i thinks you bought a pan that has been tapped to a larger size..
i have not seen any difference in size myself from 77-86 550-1150.
someone correct me if i'm wrong.

[Scudder]

Thanks. That make more sense. Back to the drawing board.

Scudder

[BassCliff]

Hi,

Why not go to the auto parts store and get an oversized plug that fits? Seems like a simple solution. If the pan is good, just get a plug that fits.


Thank you for your indulgence,

BassCliff

[bwringer]

It's possible that someone Helicoiled the pan and the Helicoil came out with the old drain plug, which they often do.

Do the threads look sharp and freshly cut and definitely a lot bigger, or just stripped out and the next oversize drain plug put in?

If you have the pan in hand, a decent machine shop should be able to put in a permanent steel thread insert that will end the problem forever. The stock drain plug thread is 14mm diameter X 1.25 pitch, which is the same as the common spark plug thread, so there are plenty of inserts available.

The problem is finding a decent machine shop...