Results 1 to 8 of 8
  1. #1

    Head compression comparison #'s 06 GPR 1300

    Did a search and found conflicting info. Understanding that #3 compression is lower than 1 & 2, what is everyone going with, the same in all three, or lower in #3? Are their reliability issues with say going 150/45cc in all 3?


  2. #2
    milling the stock head will keep the same variance with number 3 being slightly lower.
    a milled OEM head will put you in the 145, 145, 142... +-...

  3. #3
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Location
    Minden, Nevada, United States
    Posts
    10,664
    +1
    11
    We drop compression on #3 on the 03' to current EFI ski's because of the ECU not dropping the timing like the 00'-02' CDI ignition ski's.

  4. #4
    Quote Originally Posted by WATER WOODY View Post
    We drop compression on #3 on the 03' to current EFI ski's because of the ECU not dropping the timing like the 00'-02' CDI ignition ski's.
    woods, I thought the head was designed for lower compression in that cylinder???

  5. #5
    Woody..bummer! I was afraid of that. I know some guys are runnin an extra gasket in #3 to help w/deto.. So, what's the deal, if I use the standard 150 across the board like most folks, (and reep the benefits of higher compression in #3) and since I have a FF exhaust & D-plate to cut temps, if I make sure I go w/ min. 91/92 Octane, do you think I'm OK (?)

    BTW, I'm runnin a cooler plug.

    I guess too, if these aftermarket guys are sellin this stuff w/o warning folks, hell....I'm gonna suuuuuuuuuuuuuuuuuu

    PS, maybe if I set my controller always on the rich side... .

  6. #6
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Location
    Minden, Nevada, United States
    Posts
    10,664
    +1
    11
    You need to drop compression on #3 at 5 psi less

  7. #7
    Quote Originally Posted by WATER WOODY View Post
    You need to drop compression on #3 at 5 psi less
    hmm thats weird, my #3 is less by a few #`s and as far as i know it was just milled

  8. #8
    Happily Self-Employed WFO's Avatar
    Join Date
    Nov 2005
    Location
    Houston, Texas
    Posts
    12,801
    +1
    450
    Quote Originally Posted by WATER WOODY View Post
    You need to drop compression on #3 at 5 psi less
    +1

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Yamaha GP1200R burning pistons with R&D head? Compression to high?
    By Quottro in forum Yamaha PWC Performance (2-stroke)
    Replies: 8
    Last Post: 11-06-2011, 06:17 PM
  2. 720 Stock head compression 150?
    By vshockey10 in forum 2-Stroke Performance
    Replies: 3
    Last Post: 04-28-2010, 02:46 PM
  3. riva head only 135 compression
    By MB VIP in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 08-12-2007, 12:30 AM
  4. 48cc dome on 1300 head = ? compression
    By NateGP1300R in forum Yamaha PWC Performance (2-stroke)
    Replies: 6
    Last Post: 05-31-2006, 06:42 AM
  5. head compression, keyway..?
    By titi0314 in forum Yamaha PWC Performance (2-stroke)
    Replies: 9
    Last Post: 04-06-2006, 10:12 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •