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  1. #1

    Higher compression heads with cat

    I have a high compression head that i will put on in the winter, but i still have the cat in my 2005 GP1300R. Is it necessary to put in the D plate too ( I have that too but i have to find it and it looks to be a lot more work than changing the head ) or just a good thing to do eventually ?

  2. #2
    007GPR08's Avatar
    Join Date
    Apr 2009
    Do you have to? No. But since a shaved head will raise cylinder temps you're best off removing the cat to help keep temps down. Besides the cat won't last forever anyway & will eventually come apart. Put the D plate in is my advice. If you can't find it then order a new one...they are fairly cheap.

  3. #3

  4. #4

    Join Date
    Jan 2006
    Texas City, Texas
    As stated, the cat con will eventually go bad. The cat con not only provides back pressure to aid in exhaust scavageing (which the "D" plate compensates for) it also generates heat. High heat is needed for the stinger pipe to operate as designed.

    Many people have reported a loss of about 50 top end rpms when they went from the cat con to the "D" plate presumeably because the pipe was a tad to cool. To compensate for this loss of rpms, some have taken one of the two cooling water return lines that goes from the head to the exhaust pipe and rerouted one of them over board. This lack of cooling water to the exhaust pipe allows the pipe to get hotter and back to original operating temperature.

    Just remember that replaceing the head and the cat con are two seperate actions that both effect how your engine operates . It is best to mod the head first, along with the changes that will be made with your fuel injection and test with an aftermarket tach to determine your best rpms, THEN replace the cat con to see how your best rpms were effected. If you have lost any rpms, dump some water overboard as prescribed.

  5. #5
    silver93t's Avatar
    Join Date
    Jun 2012
    I have a d plate for sale in the classifieds.

  6. #6
    have one of those somewhere in the deepest depths of my garage, saw it last spring

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