Results 1 to 6 of 6
  1. #1

    Join Date
    Aug 2009
    Location
    McKinney, TX
    Posts
    124
    +1
    1

    Rebuilt 1300 compression

    Just purchased a rebuilt 1300 motor and did a bench test on the compression. Numbers were 118, 126, 122 with a snap on gauge. Question- with 0 hours on the motor, do those numbers mean much or will they change and maybe level out after break in? Stock oem new pistons with oem cylinders with 10 hours on them, stock head. Everything looks and feels great but the numbers are throwing me off??? Thoughts?


  2. #2
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
    Join Date
    Nov 2005
    Posts
    6,194
    +1
    536
    Quote Originally Posted by richte18 View Post
    Just purchased a rebuilt 1300 motor and did a bench test on the compression. Numbers were 118, 126, 122 with a snap on gauge. Question- with 0 hours on the motor, do those numbers mean much or will they change and maybe level out after break in? Stock oem new pistons with oem cylinders with 10 hours on them, stock head. Everything looks and feels great but the numbers are throwing me off??? Thoughts?
    when the motor breaks in compression will go up.

  3. #3
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Location
    Minden, Nevada, United States
    Posts
    10,664
    +1
    11
    What was the cranking rpm when you did the test?
    Was the throttle wide open?

  4. #4

    Join Date
    Aug 2009
    Location
    McKinney, TX
    Posts
    124
    +1
    1
    It was a bench test with a fresh battery direct to the starter. It was spinning over very easily. No exhaust manifold on or anything installed on the intake side of the block.

  5. #5
    WATER WOODY's Avatar
    Join Date
    Aug 2005
    Location
    Minden, Nevada, United States
    Posts
    10,664
    +1
    11
    Test it again when the motor is in.

  6. #6

    Join Date
    Aug 2009
    Location
    McKinney, TX
    Posts
    124
    +1
    1
    I realized the head has some pitting on the cylinder with low compression which I believe is causing the lower than normal reading. Any way to salvage the head? It's stock.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. SOLD Rebuilt 1300 Reeds with Riva Boyessen stuffers
    By FXSlowKroozer in forum Yamaha 2 Stroke Skis
    Replies: 0
    Last Post: 01-26-2015, 10:10 AM
  2. bought 780 rebuilt no compression
    By johnnyrod in forum Polaris How To & FAQs
    Replies: 4
    Last Post: 07-24-2008, 10:52 PM
  3. What compression will 35cc domes produce in a 1300?
    By NateGP1300R in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 05-16-2007, 09:42 AM
  4. 1300 no compression rear cylinder
    By OCFZR in forum Yamaha PWC Performance (2-stroke)
    Replies: 25
    Last Post: 08-31-2006, 08:05 AM
  5. 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

Posting Permissions

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