I was wondering if anyone on here knows what the thread size and tap size for the chaincase on a 1990 flstc, the thread on mine is in need of a bit of a clean up.

 

mick

I don't know what size for your model bike,,, but,, if your thread is stripped, (or about fucked),, you will need to install an insert of some kind.. You could just drill and tap a larger hole, and buy a new drain plug , (with magnet), to suite.. My advice would be a solid insert , commonly called a Timesert,, that will fit your original drain plug.. As it is your primary oil drain hole , it wont be to difficult , as it is vertical, and good access to drill and tap. Google "installing a timsert" ,, it will show you all the do's and dont's ...
If you go the Timesert way,, when installing the insert , put some red Loctite on its threads ..

After you finish the job,, buy some cheap oil and flush the bottom of the primary and drain hole out , to remove any metal pieces from your drilling and tapping that may be have gone up into the primary area !! Hope this helps ...

thanks for the info markwoumla, I have to pull the outer chaincase to replace the stator ect so I can do the drain hole thread while the outer cover is off the bike.

mick

gas presure plug taperd thread