Page 1 of 2 1 2 LastLast
Results 1 to 10 of 11
  1. #1
    Chine Walker
    Join Date
    Nov 2006
    Posts
    598

    Is it normal for the cylinders not to be the same size?

    While looking at my 1300 cylinders, I noticed the middle (#2) cylinder had a different bore #. Cylinders 1 & 3 have a "12" stamped on them and #2 has a "14 on it. Is this normal? As per the manual the #'s fit within the green piston group.
    On a seperate topic; would it make sense, while building a custom motor, to use different bore cylinder/piston set for each cylinder, since it seems that each cylinder runs at different temps and air/fuel ratios? What I'm trying to ask is, would it make sense to have different cylinder to piston clearance #'s for each of the 3 cylinders, since they don't seem to burn fuel the same?
    Thanks,
    jp
    Last edited by jpa1300; 08-20-2007 at 10:14 PM.


  2. #2
    Tennessee's Avatar
    Join Date
    Dec 2005
    Location
    Mt. Juliet, Tn
    Posts
    502
    +1
    2
    The tolerences are so close once the cyl. is finished they measure it and fit the correct piston in it. I think there is only something like .002" difference from the largest to smallest available.

  3. #3
    Chine Walker
    Join Date
    Nov 2006
    Posts
    598
    So it really wouldn't make much of a difference playing with the clearance factor in a custom rebuild.
    Thanks,
    jp

  4. #4
    Tennessee's Avatar
    Join Date
    Dec 2005
    Location
    Mt. Juliet, Tn
    Posts
    502
    +1
    2
    I think it is pretty important. I had a brand new motor with the wrong size piston in a hole and it only made it 11 minutes. I did the install and Riva was still able to get it replaced under warranty since it was obvious. I would say too tight and you will have trouble. A little loose might be ok, but not good for performance.

  5. #5
    Chine Walker
    Join Date
    Nov 2006
    Posts
    598
    Tennessee:
    I wonder what the magic combo within Ymaha's tolerance range works best. The book states specific piston groups for specified cylinders (depending on what's stamped on the cylinder); I've read some posts that recomend the smallest piston group for the largest cylinder groups. I believe the thinking behind this was yamaha's very tight tolerances and the different expansion rates between the forged aluminum pistons and the Nikasil cylinders. The author of the post felt the tight Yamaha tolerance would promote sticking a piston easily should you run into a lean or lubrication issue.
    I new to the 2 stroke motor and I'm trying to get a grasp on how to read the proper air/fuel ratio. Plug readings give me trouble due to the oil variable(not to mention reading the piston wash patern, which is totally new to me).
    On a 4 stroke, I have an easier time reading the plugs, plus I have a wide band O2 sensor that helps me obtain the right AFR data.
    The odd thing is that my second hobby is tuning air cooled 4 stroke motors which coincidentaly have the same piston/cylinder material combo (forged Mahle pistons with Nikasil lined cylinders). Those motors are usually built on the "loose" side due to the different thermal expansion rates.
    Regards,
    jp

  6. #6
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    Location
    United States
    Posts
    11,875
    +1
    30
    Match the pistons to the cylinders both oem and Pro-X come in different sizes to match the cylinder #s and it is common to have different numbers.

  7. #7
    Chine Walker
    Join Date
    Nov 2006
    Posts
    598
    Thanks Bill.

    jp

  8. #8

  9. #9
    Duke's Avatar
    Join Date
    Jul 2006
    Location
    Florida
    Posts
    10,004
    +1
    406
    Quote Originally Posted by TennesseeRXP View Post
    The tolerences are so close once the cyl. is finished they measure it and fit the correct piston in it. I think there is only something like .002" difference from the largest to smallest available.
    Actually its more like .0006 not .002. Barely over a half a thousandths between smallest to largest.

  10. #10
    Moderator OsideBill's Avatar
    Join Date
    Mar 2006
    Location
    United States
    Posts
    11,875
    +1
    30
    The 1200R manual shows the cylinder numbers to be 80.0XX where you replace the X with the number of the cylinder ie: #12 cylinder is 80.012mm. So the cylinders range from 0-18 or 80.000-80.018mm or 3.1496-3.1503 inches for a total variance of .0007 inches
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	GPR piston size.jpg 
Views:	40 
Size:	73.3 KB 
ID:	35859  
    Last edited by OsideBill; 08-21-2007 at 10:17 AM.

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. Replies: 3
    Last Post: 08-25-2016, 09:59 AM
  2. Replies: 9
    Last Post: 07-02-2016, 07:56 PM
  3. Replies: 6
    Last Post: 09-06-2013, 06:02 AM
  4. Hot water from the PUMP while on hose, Is it normal for a 300lx??
    By cphillips1982 in forum Kawasaki Open Discussion
    Replies: 11
    Last Post: 03-18-2012, 01:44 AM
  5. FORT… INJECTOR TREATMENT is it safe for the GPR ?
    By spaceman in forum Yamaha PWC Performance (2-stroke)
    Replies: 6
    Last Post: 12-12-2008, 11:55 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
  •