Results 1 to 4 of 4
  1. #1

    Join Date
    Apr 2012
    Spring hill, Florida

    99 gp 1200 rebuild and mod

    I'm new to forum and I need some help deciding on some performance mods. I'm in the middle of rebuilding top end and switching ski to premix. I was thinking about the following mods:m
    aftermarket head
    aftermarket spark arresters
    d plate
    what are your thoughts on those mods?
    Any additional mods?
    the ski is a 99 gp1200 non power valve

  2. #2
    Flying Scotsman's Avatar
    Join Date
    May 2006
    No D plate on GP thats for GPr .
    Head with domes,yes.
    Reeds are expensive but nice they give a little throttle response.
    Flame arrestors,yes.
    Porting the cylinders is expensive but well worth the $$
    Increasing displacement with big pistons also expensive but worth the $$$.
    Dial the hull in to get the nose out of the water then dial in the impeller so you turn 6800 rpm or so and your good to go.If you have a stock CDI you need to stay off the rev limiter.

  3. #3
    whats the problem with the rev limmiter and the stock cdi? isnt it just a ignition cut?

  4. #4
    when i just re built mine i did 1mm over sized pistons, went to 40:1 premix, a light port, shaved the stock head to 140 psi, and together with my worx intake grate and sponsons and 97 gp ride plate with 2 shims at the back, i get 107kph all day every day on gps at aprox 6900-7000 (on dash).. which keeps me happy

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. 98' GP 1200 Rebuild. help
    By rebelchild41 in forum Yamaha Old School Skis
    Replies: 4
    Last Post: 07-10-2010, 07:13 PM
  2. 2004 RXP - Rebuild / Mod Suggestions
    By RMcElarney in forum 4-Tec Performance
    Replies: 5
    Last Post: 06-30-2010, 04:22 PM
  3. need advice on xl 1200 rebuild
    By Jasond in forum Yamaha PWC Performance (2-stroke)
    Replies: 7
    Last Post: 01-08-2010, 06:21 PM
  4. XL 1200 rebuild
    By wojo14 in forum Yamaha Projects & Build Threads
    Replies: 6
    Last Post: 08-12-2009, 07:08 PM
  5. I need to rebuild GP 1200
    By GYTWYPT in forum Yamaha Old School Skis
    Replies: 73
    Last Post: 03-16-2008, 01:36 PM

Posting Permissions

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