Please read this......and anything else you might find on the Act online, this is just one place to get an idea of your rights
The Magnuson Moss warranty act in short says that a warranty must be clearly written and understandable by an average person. Also any statements that are ambiguous are held agaisnt the drafter of the warranty, NOT the consumer.
It states that the burdon of proof falls on the manufacturer to prove that something you did DIRECTLY effected the part or parts being warrantied for failure.
This basically means that they CAN NOT void your entire warranty based on the replacement of any part. They can ONLY void it on parts that are directly affected by the part you replaced.
A few examples
If you change your exhaust, and you can show that the air fuel ratio was corrected and/or within a range that would NOT cause a failure the warranty on your motor cannot be voided unless stated so in the warranty. They obviously can void it on any part of the exhaust affected by the parts changed.
If you change your brake lines, and your motor blows... they can not void the warranty on the motor. Even to the point of changing motor parts. they have to prove it CAUSED the failure. Example being you put an aftermarket slipper clutch in PROPERLY, and the pistons seize. Mechanically one cannot effect the other if installed properly, and thus the only voided part of your bike is the clutch... nothing more.
KNOW YOUR RIGHTS, and cover your ass. Dont let anyone try to tell you your warranty is voided when you take it in to a dealer, and you know there is no way anything you did caused the failure.
If they do, and refuse to work on it, escalate the problem to a higher office. It WILL get remedied.