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  1. #1
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    Yamaha 1100 vs 1200 exhaust question

    Does anyone know if using a Yami 1100 expansion chamber on a 1200 motor will increase bottom end power or top end RPM? I have heard there is supposed to be a performance increase but I'm looking for more information.
    Thanks
    James
    1996 XP All the usual mods
    http://www.pwctoday.com/showthread.p...17#post4380117

    1996 WaveBlaster II 1200 conversion in progress
    http://www.pwctoday.com/showthread.php?t=477231

  2. #2
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Yamaha 1100 vs 1200 exhaust question

    The stinger size is a bit smaller on the 1100. I'm pretty sure in 99 they they reduced it to 1100 size on the 1200. It helps give a bit more top end.
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  3. #3
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    Re: Yamaha 1100 vs 1200 exhaust question

    Quote Originally Posted by Myself View Post
    The stinger size is a bit smaller on the 1100. I'm pretty sure in 99 they they reduced it to 1100 size on the 1200. It helps give a bit more top end.
    I think your right, I just looked up the part numbers and the part number for the 1100 (63M-41121-00-94) is the same as the 99 GP1200 part number
    The 97/98 GP1200 part number is 65U-41121-00-94.

    I think I also read somewhere that the the 63M chamber only has two water injection ports at the end of the inner chamber where the 65U has three water injection ports.
    Can anyone confirm?
    1996 XP All the usual mods
    http://www.pwctoday.com/showthread.p...17#post4380117

    1996 WaveBlaster II 1200 conversion in progress
    http://www.pwctoday.com/showthread.php?t=477231

  4. #4
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    Re: Yamaha 1100 vs 1200 exhaust question

    So I found some more information but just as confused as ever....
    I have heard from racers back in the day that running a 1100 pipe was a popular mod. GroupK, who I highly respect, saysrunning an 1100 pipe on a 1200 requires race gas. The 99 GP1200's use the 1100 pipe with pump gas but I also read that the Riva CDI is only for use on 97-98 GP1200's which make me wonder if the 99 GP1200's also have different timing curves that make it possible to run on pump gas????

    Anyone know if the 99GP1200's use a different timing curve than previous 1200's?
    1996 XP All the usual mods
    http://www.pwctoday.com/showthread.p...17#post4380117

    1996 WaveBlaster II 1200 conversion in progress
    http://www.pwctoday.com/showthread.php?t=477231

  5. #5
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    Re: Yamaha 1100 vs 1200 exhaust question

    I am not aware of any difference between them besides the exhaust.

  6. #6
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    Re: Yamaha 1100 vs 1200 exhaust question

    if i remember the grey color pipe was only in the 1100 and works fine but if you put the grey to the 1200 65u motor there is detonation on the pistons i think that all the gp1200 and suv and xl1200 using the same pipe color blue . tim judge using grey color pipe in their motors but i never discuss if is using race gas .

  7. #7
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    Re: Yamaha 1100 vs 1200 exhaust question

    iptamenos, I got you message but your inbox is full
    1996 XP All the usual mods
    http://www.pwctoday.com/showthread.p...17#post4380117

    1996 WaveBlaster II 1200 conversion in progress
    http://www.pwctoday.com/showthread.php?t=477231

  8. #8
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    Re: Yamaha 1100 vs 1200 exhaust question

    No on the timing curves theory as ALL 1200s use the same cdi including jet boats.

  9. #9
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    Re: Yamaha 1100 vs 1200 exhaust question

    All 1100 are silver 63M pipe.
    97 GP1200 is silver 65U.
    98 GP1200 is blue 65U.
    99 GP1200 is blue 63M.

    63M pipe can safely be run on the 1200, no mods or race gas required.

  10. #10
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    Re: Yamaha 1100 vs 1200 exhaust question

    Quote Originally Posted by SkiSwede View Post
    All 1100 are silver 63M pipe.
    97 GP1200 is silver 65U.
    98 GP1200 is blue 65U.
    99 GP1200 is blue 63M.

    63M pipe can safely be run on the 1200, no mods or race gas required.
    From what I have learned you are correct.

    IMO, The 63M pipe can be used with 41cc (or bigger) domes but higher compression or advanced timing (Riva CDI) and 63M pipe requires race gas.
    1996 XP All the usual mods
    http://www.pwctoday.com/showthread.p...17#post4380117

    1996 WaveBlaster II 1200 conversion in progress
    http://www.pwctoday.com/showthread.php?t=477231

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