Ummm. How? It has already been established that the O-ring last for up to (8) oil changes. The gaskets last (1) one. That was my point. O-rings don't cost $80 like (8) gaskets do. I understand aftermarket ones, but the MoCo very easily could fabricate ALL derby covers to use an O-ring and save the user money. Hence, my Gomer statement.

 

Yes, but the flat gaskets are from after-market derby covers & they're made by a variety of vendors/suppliers so, unless you swap, the o-ring is std...still agree to disagree on both points. That's your prerogative so...do what you believe saves your pocketbook, but let others choose how/what they want to maintain their rides w/o the snarky comments.

These forums are for help vs. cyber playground bullies...

 

You can use the same flat gasket a bunch of times too.

Just use the right gasket for the job...

 

Some people you just can't reach.... Harley Davidson is the maker of Derby covers that do not allow an O-ring. They are the same company that supplies the stock covers. What is so difficult to understand?
And just because you don't understand something, doesn't mean someone is being "snarky". I just might mean someone is trying to make you understand. Please don't lecture just because you don't agree on something.

 

I have at least 6 or 7 different derby covers sitting in a box in my garage, all built by HD from the parts and accessories catalog for my twin cams, all of them take an o-ring. As a matter of fact the only derby covers I've seen that don't are either from early twin cams or evo and older bikes, or aftermarket parts offered from an outside manufacturer....

 

Then you may not want to order the Harley Davidson Motor Co. derby cover, part # 25338-99A. This requires a gasket Part # 25416-99C in lieu of the O-ring on your other covers.
http://www.harley-davidson.com/store...04-2533899a--1

 

Interesting. What derby covers do you have?

I looked real quick and didn't see one 99-2015 derby listed that didn't take the flat gasket.
They may have gone strictly to o-ring with the narrow-primary but I could not confirm.

 

My flat gasket is on its 4th tour. Dunno if I'll get 8 changes out of it but if handled/installed with reasonable care these are a multi-use item too.

Whatever you use, just have a spare on hand and use the seal thats in service until it does leak,, then change it and order a new spare. "O"-rings in particular are very durable.

 

 

​​​​​​​Whew! Glad that finally got cleared up! Haven't had a stock derby cover in a long time. So... good advice. If you do not want to line the MoCo's pockets, stick with the OEM cover!