Crush washer

[yamrider1]

Hi everyone.
Ok so here goes. Does anyone one have a definitive answer as to which way up the oil drain plug crush washer is fitted. One side has a flat surface and one side has a cone shaped side. I've tried googling it but there are many that say flat side to sump and cone/tapered side to head of sump bolt so the steel head of the bolt does the actual crushing and not the soft aluminium of the sump. Others say the other way round so the taper on the washer crushes into the sump top threads to form a good seal. I must admit I have never been in favour of crushing anything into an aluminium thread so have always gone with the flat surface side of the washer to the sump.
I know this may be an age old question but I am interested as to which way is the correct way.
Regards,
Glyn.

 

[Isleoman]

I may never know as I’ve never taken mine off over hundreds of thousands of miles and oil changes every 3000. Never changed the ones in my cars or trucks either.

I’m livin on the edge societal collapse with this radical approach.

I suspect it makes no difference.

It’s gonna get crushed either way you place it.

 

[Vic 09 FZ1]

I may never know as I’ve never taken mine off over hundreds of thousands of miles and oil changes every 3000. Never changed the ones in my cars or trucks either.

I’m livin on the edge societal collapse with this radical approach.

I suspect it makes no difference.

It’s gonna get crushed either way you place it.

When i was a youngster i did this same thing (reused old washer)with all my car oil changes ..and (sadly ) at the same age i wouldve done the same with my bike(s) too…if i ever changed the oil on them lol….now i change the washer (on both auto and bike) and ive concluded out of frustration of contradicting online sources . …That which ever way that doesnt leak for you is the right way lol. For me i put the flat against the housing /pan cause it seems to make more sense to as that side doesn't rotate and more apt to lay flat and seal …but this is a guess and has worked so far for me

 

[Eff-Zed-1]

Every crush washer I've removed on Yamaha had the flat surface seated against the bolt. But I personally swap to Honda crush washers on all my Yamaha bikes. Only exception is on the final drive on the FJR that has a Dowty washer on it.

 

[CobaltFZ1]

You can change the crush washer? LOL! Who knew?