Need to understand that there are two different warranties involved. There is the regular POS 2 year warranty that supposedly covers everything. Then there is an Emission Systems Warranty that just covers the stuff that affects emissions. If you remove a cat or tamper in any way with the emission system (SERT/PCIII/ etc.) the emission system warranty is toast. However, that does not void the rest of your regular warranty. Read the Magnusson-Moss Warranty Act of 1975. Sure, you may have to consult with an attorney to get the MoCo to comply with the law. That's true any time you deal with less than honorable companies or people.
BTW - Do you really think a dealer is going to pull your mufflers and look up your headpipe with a flashlight to make sure you didn't remove the cat? I'd be surprised if very many of them outside of California even know there is a cat. If you don't tell them, or ask them to do it for you, I wouldn't sweat it. If you're really worried about the warranty, then don't drill the cat out, just change headpipes to the non-cat version and save the originals. If the engine blows up, swap the pipes before you call the dealer to come haul it away.
Jerry
HARLEY-DAVIDSON EMISSION CONTROL SYSTEM WARRANTY
The following warranty applies to the emission control system and is in addition to the LIMITED WARRANTY, and NOISE CONTROL SYSTEM WARRANTY.
Harley-Davidson Motor Company warrants to the first owner and each subsequent owner that this vehicle is designed and built so as to conform at the time of sale with applicable regulations of the U.S. Federal Environmental Protection Agency at the time of manufacture and that it is free from defects in materials and workmanship which cause this motorcycle not to meet U.S. Environmental Protection Agency Standards within 5 years or 18,641 miles (30,000 kilometers) whichever occurs first.
The warranty period shall begin on the date the motorcycle is delivered to the first retail purchaser or, if the motorcycle is placed in service as a demonstrator or company vehicle prior to sale at retail, on the date it is first placed in service.
THE FOLLOWING ITEMS ARE NOT COVERED BY THE EMISSION CONTROL SYSTEM WARRANTY
1. Failures which arise as a result of misuse, alterations, accident or non-performance of maintenance as specified in the Owner’s Manual.
2. The replacement of parts (such as spark plugs, fuel and oil filters, etc.) used in required maintenance.
3. Loss of time, inconvenience, loss of motorcycle use or other consequential damages.
4. Any motorcycle on which the odometer mileage has been changed so that the mileage cannot be determined.
RECOMMENDATIONS FOR REQUIRED MAINTENANCE
IT IS RECOMMENDED THAT ANY EMISSION SYSTEM MAINTENANCE BE PERFORMED BY AN AUTHORIZED HARLEYDAVIDSON DEALER USING GENUINE HARLEY-DAVIDSON REPLACEMENT PARTS. THE MAINTENANCE, REPLACEMENT OR REPAIR OF THE EMISSION CONTROL SYSTEM MAY BE PERFORMED BY ANY OTHER QUALIFIED SERVICE OUTLET OR INDIVIDUAL. NON-GENUINE PARTS MAY BE USED ONLY IF SUCH PARTS ARE CERTIFIED TO COMPLY WITH U.S. ENVIRONMENTAL PROTECTION AGENCY STANDARDS.
Harley-Davidson Motor Company, P.O. Box 653 Milwaukee, Wisconsin 53201, U.S.A.