Page 1 of 2 1 2 LastLast
Results 1 to 10 of 16
  1. #1

    piston matching?

    I am putting together a top end for a 1200pv. I have seen quite a few for sale with pistons. these cylinders do not neet plating this would save money. should I have the ones I got and replate and use 3 new matching pistons or can I mix and match. seems like balance might be a problem


  2. #2
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    Location
    League City, Texas
    Posts
    16,066
    +1
    23
    Is this going to be a heavily modded motor? or mostly stock motor?
    Are you talking about mixing OEM Yamaha pistons and Pro-X or Wiseco pistons?

    I would keep all the pistons alike in brand

  3. #3
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    Location
    League City, Texas
    Posts
    16,066
    +1
    23
    Now, I'll say this.....for the motor I built for my GP1200R, I was looking for harmony in the motor I built. But I had alot of bolt on mods...reeds, 46mm carbs, 150 psi compression, flame arrestors, HO pump, dynafly impeller ect.....yada yada yada...

    now, I had a trued and welded crank. So, just to picky, just me, it probably was not necessary, I purchased 5 Pro-x pistons. 5 sets of wrist pin bearings.

    I weighed all 5 and kept the 3 closest in weight together. I also kept the 3 wrist pin bearings closest in weight together. I then kept the other two as spares.

    Not sure if it was really needed for my mostly stock non-ported setup, but I wanted to extract every little bit of possibly precision gain I could from my motor as I was aiming for a personal goal to see how fast I could stretch my motor in a non ported setup. Well, after 160 or 180 hours later, the motor was still in perfect condition when I sold it. I have pics of the 100 hour inspection and I stayed on top of the preventative maintenence like an shoe made of an eggshell.....so

    it depends on what your trying to do. If this is a stock motor, recreational motor, I would still try to atleast keep the brands of pistons the same.

    Also search the forum and do some bulletproofing modifications that help give longevity to your motor. If it is a GPR, don't forget to reinforce the tunnel. Be meticulous when assembling your engine. torque everything to spec also.

    ask questions, we are here to help.

  4. #4
    Lake Mead Bum & BTLS Mark starflight's Avatar
    Join Date
    May 2007
    Location
    Boulder City, NV
    Posts
    3,364
    +1
    1
    Just curious, how much did the weights vary on the pistons and bearings?

  5. #5
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    Location
    League City, Texas
    Posts
    16,066
    +1
    23
    the bearings didn't vary hardly if any.....

    The pistons if I remember correctly varied from .3 - 1.5 grams apart. Not much it sounds, but when that rotational mass is moving, it weighs much more

    I used a shipping scale to do this
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	CIMG1867.JPG 
Views:	50 
Size:	1.87 MB 
ID:	107887  

  6. #6
    CHICKA WAH WAH bren's Avatar
    Join Date
    Sep 2007
    Location
    Cairns, Australia
    Posts
    595
    that weight check / match is a bloody good idea !

    I was just thinking (yes it hurt) if the suppliers would weight match them if you asked them. Mind you, could you trust their scales !!

  7. #7
    Lake Mead Bum & BTLS Mark starflight's Avatar
    Join Date
    May 2007
    Location
    Boulder City, NV
    Posts
    3,364
    +1
    1
    Quote Originally Posted by RX951 View Post
    the bearings didn't vary hardly if any.....

    The pistons if I remember correctly varied from .3 - 1.5 grams apart. Not much it sounds, but when that rotational mass is moving, it weighs much more

    I used a shipping scale to do this
    Thanks for the info! Never would have thought about that. Makes sense.

  8. #8
    I know that Lowell always balances the pistons on his motors so they are all exactly the same weight. Don't know how much difference it makes but there must be something to it.

  9. #9
    I asked a friend who had a ski repair shop about balancing the engine and he had never heard of such a thing. when I was a kid i boared a 455 pontiac .30 over and had the rotating assembly ballanced. you weigh the rods pistons and rings. to ballance you simply grind the rod a bit. I assume the crank in a two stroke is balanced before or during assembly. I wonder if you could simply grind on the piston to lighten them

  10. #10
    kind of off topic but I read about tunnel reinforcement. Is it that important for a rec gpr 1200

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Rebuilding a 97' gp1200 piston matching
    By mking in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 10-19-2013, 07:02 AM
  2. Replies: 1
    Last Post: 02-12-2013, 11:18 AM
  3. Why do you have to match pistons like this??
    By darrengee in forum Yamaha PWC Performance (2-stroke)
    Replies: 5
    Last Post: 05-06-2009, 02:29 PM
  4. WTB GP1200R PV cylinder/matching piston
    By tfergusonracing in forum Yamaha Classifieds
    Replies: 3
    Last Post: 03-26-2009, 01:42 AM
  5. WTB Ready to use cylinder and matching piston for 2001 GP1200R
    By RetiredWW in forum Yamaha Classifieds
    Replies: 4
    Last Post: 09-14-2008, 08:50 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
  •