i'm seeing a fair amount of fuel pump issues lately as our beloved buells continue to age gracefully. several on-going discussions on this board as well. the removal/replacement/upgrade/cross-over scenarios have been well covered but there continues to be consistent questions regarding the O-rings. everything you can possibly need to know to source same.
ALL XB MODEL FUEL PUMP FRAME TO PUMP MOUNTING O-RINGS
1-factory part # is P0121.02A8 SUPERSEDED by same # with an A as suffix. the A means nothing. just a vendor tracer. both part numbers reference the same identical part. still available in unlimited dealer quantities as of 3-22-2017
2-available thru many aftermarket suppliers such as OringsandMore.com IMPORTANT: any replacement ABSOLUTELY must be either nitrile or viton or it will leak like hell in short order.
O-RING SIZE IS: 3 inches ID-------3/16th inches thickness. these are the 2 dimensions you will need to source any aftermarket replacements
3-OringsandMore.com great source and priced right. their part # is 151V.
4-i keep O-rings in stock. dealer retail is approx. $6.20 each.....my cost $3 each. if you get stuck PM me and i'll send you some.
NOTE: each ring must be lightly coated with either recommended silicone O-ring lube or a light grease prior to assembly. and carefully tighten the bolts in sequence as to not crack the pump housing.
hope this info helps.