When I changed my Derby cover I used the one on the left.

 

+1 my bike is a 2006 and on it's second orange o-ring. Only because I was stupid and tossed out a perfectly good one changing my primary factory fill at 500 miles. If you torque the derby screws to 100 INCH LBS in a star pattern you won't damage the gasket. Be sure to index your derby cover to it's original position. I scribed an arrow on the inside of mine indicating the top hole.

 

Same here. My pops sent mine out for etching ande I used his extra until mine came back. I have had 3 covers on there and they all worked with the frisbee.

 

When I changed my derby cover to the willie g skull cover, my 04 FXDLI had the one on the left on it. I reused it, when I took off the original cover the gasket stay on perfectly.

Jay

 

yea ive got flat one on my 2001 fxdl been on and off several times works great

 

I use the one on the left also. have it on my '06 WG and also one on my '07 UC. I replaced it on the first primary service, and have re-used it many times. it replaces the o-ring with no problems.

 

It appears that you could use either one with perfectly acceptable results. I two have reused my o-ring type a bunch o'times with no problems.

 

Question about the o ring type, they original derby cover has a grove for the gasket and the other covers I have seen do not ??? Do you just put the gasket back into the grove on the primary side and not worry about the cover ?

 

The newer bikes like I think 07(?) and up stock derby covers that have an o ring groove in them. These are the ones that require the o ring. The accessory covers are the 06(?) and older style that don't have the o ring groove and use the flat frisby gasket. You can't use the o ring with the non o ring covers.
My 08 fatbob does not have an o ring groove in the primary. It is just a flat surface that the o ring or flat gasket can mate up to depending on which cover you have.

 

My 08 Fat Bob has the groove for the o ring, I tried the other gasket when I switched to a denim black cover and torqued the bolts to 100 lbs, but it still leaked and had to switch back to the other chrome cover