Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12
  1. #1

    Join Date
    Aug 2013
    Location
    Atl Ga
    Posts
    4

    Dropped a Power Valve time for complete rebuild

    First time poster long time reader looking for advice. I have a 2000 800xl that has dropped the pv on the front cylinder. Yes I have the clips, however never bothered installing them, guess I'm paying for it now. I have completely disassembled the motor including splitting the case. Head appears to still be good, not sure if piston and cylinder can be reused. Crank is in need of new bearings on front connecting rod, all other parts of crank appear to be okay. My thoughts were to send crank to crank works per all the recommendations on here. I have a few questions. First is it okay to reuse a case that has deep scratches in it? Scratches are from the connecting rod not having enough clearance after bearing failure. There are no holes or cracks in it, hoping to sand rough spots and reuse. Cylinder has some scratches on the lower 3/4 of it detectable with finger, not deep but still there, is there a way to remove without re-plating? Piston as a few spots on the top edge from contacting the pv well above the rings, can I just replace the rings with a slight loss of compression or does it have to be replaced? Do you reuse wrist pin and bearings or replace? Trying to keep the rebuild cost at a min. Sorry for all the questions as I know I'm in over my head. Any thought or recommendations would g be greatly appreciated. Click image for larger version. 

Name:	2013-08-08_22-58-57_628.jpg 
Views:	51 
Size:	45.6 KB 
ID:	309742Click image for larger version. 

Name:	2013-08-08_22-59-19_994.jpg 
Views:	51 
Size:	81.7 KB 
ID:	309743Click image for larger version. 

Name:	2013-08-08_22-52-47_178.jpg 
Views:	58 
Size:	43.2 KB 
ID:	309741


  2. #2
    Banned User
    Join Date
    Aug 2011
    Posts
    5,049
    +1
    238
    Ouch break open your wallet!

  3. #3

    Join Date
    Aug 2013
    Location
    Atl Ga
    Posts
    4
    Thanks.... Figure I'll start at the bottom and work my way up, assuming I can reuse the crank case.

  4. #4
    I definitely would not reuse the piston. I'd be surprised if the top ring would be able to float free if chunks of the power valve got pinched between the piston and the head. You also may have stress cracks in the piston body which could let go when you got it under speed and power. I don't think scratches in the case would cause much of an issue but make sure that none are really cracks.

  5. #5
    You could get a good used oem piston in the classifieds around $50, also a good used cylinder or replate yours. Pin and bearing could be reusable, just have to inspect it and make shure they were not damaged. I buy oem parts at partzilla, they offer deep Discounts.

    Aftermarket gaskets are ok, but I dont trust aftermaket seals. Just my opinion

  6. #6

    Join Date
    Aug 2013
    Location
    Atl Ga
    Posts
    4
    Thanks for all the advice. I have purchased an oem pistion, still need to get rings. Hoped to ship crank out Fri but had issue removing flywheel. Is there any difference in power valves between the 800,1200, or 1300?

  7. #7
    YudLuz2's Avatar
    Join Date
    Jun 2005
    Location
    Flowood MS
    Posts
    1,647
    +1
    110
    Waveeater clips don't keep your valves from falling down in your motor. The only thing they will do is to keep your pin from sliding out of your power valve. Even if that happens its still impossible for the pin or the valve to drop down into your motor. The valves fall into your motor only when they break at the stem of the valve. This usually happens because the stem is worn at the base, causing the valve to go deeper into your cylinder until it catches the piston. Then it breaks the valve off and it falls into the cylinder. Due to the wear at the stem, powervalves need to be removed and inspected for wear. Anything over 100 hours on the older version valves probably need to be replaced. Anytime one continue's to break valves in one cylinder, that cylinder needs replaced due to wear in the powervalve slot. The slot in the power valve of the cylinder can't be replaced. Anytime you have a cylinder renicked, or its salt water unit, the slot will wear on the cylinder quicker. Once the cylinder part gets worn it will eat up your power valve pretty quick, its the one thing that makes the Yamaha power valve motor a high risk for failures.
    Last edited by YudLuz2; 08-10-2013 at 10:59 PM.

  8. #8

    Join Date
    Aug 2013
    Location
    Atl Ga
    Posts
    4
    That makes since as to why there was no sign of the pin or shaft in the crank case. Ski is strictly used in freshwater with close to 150 hrs. I was planning on doing a cylinder exchange, hopefully they check pv tolerances.

  9. #9
    TexasZ's Avatar
    Join Date
    May 2012
    Location
    Near San Antonio, Texas
    Posts
    460
    +1
    34
    Quote Originally Posted by YudLuz2 View Post
    Waveeater clips don't keep your valves from falling down in your motor. The only thing they will do is to keep your pin from sliding out of your power valve. Even if that happens its still impossible for the pin or the valve to drop down into your motor. The valves fall into your motor only when they break at the stem of the valve. This usually happens because the stem is worn at the base, causing the valve to go deeper into your cylinder until it catches the piston. Then it breaks the valve off and it falls into the cylinder. Due to the wear at the stem, powervalves need to be removed and inspected for wear. Anything over 100 hours on the older version valves probably need to be replaced. Anytime on continue to break valves in one cylinder, that cylinder needs replaced due to wear in the powervalve slot. The slot in the power valve of the cylinder can't be replaced. Anytime you have a cylinder renicked, or its salt water unit, the slot will wear on the cylinder quicker. Once the cylinder part gets worn it will eat up your power valve pretty quick, its the one thing that makes the Yamaha power valve motor a high risk for failures.
    Thanks for the clear and easy to understand info!

  10. #10

    Join Date
    Jan 2006
    Location
    Texas City, Texas
    Posts
    1,249
    +1
    15
    Quote Originally Posted by YudLuz2 View Post
    ......... Anytime you have a cylinder renicked, or its salt water unit, the slot will wear on the cylinder quicker. Once the cylinder part gets worn it will eat up your power valve pretty quick, its the one thing that makes the Yamaha power valve motor a high risk for failures.
    You make an interesting point. Do you suspect the same thing happens with gas valves? I've lost 2 gas valves through the years and have at least 400 hours on these ported 1200 cylinders. I just figured that it was metal fatigue on the valve stems. Fortunately, no damage was done either to the cylinders or pistons due to the valve design.

    All of my cylinders have been renicked and run exclusively in salt water.

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. WTB Power Valve cut for 1390
    By smacota1 in forum Yamaha Classifieds
    Replies: 12
    Last Post: 08-11-2010, 06:56 PM
  2. WTB Power Valve Motor for GP1200r 01
    By chris1200 in forum Yamaha Classifieds
    Replies: 1
    Last Post: 06-05-2009, 04:39 PM
  3. dropped mag power valve
    By winterstick in forum Yamaha PWC Performance (2-stroke)
    Replies: 7
    Last Post: 10-05-2007, 11:04 AM
  4. HELP ! 94 B1 Blaster, Time For Motor Rebuild ?
    By Blasterguy in forum Yamaha Old School Skis
    Replies: 36
    Last Post: 09-13-2007, 01:15 PM
  5. HELP ! 94 B1 Blaster, Time For Motor Rebuild ?
    By Blasterguy in forum Yamaha PWC Performance (2-stroke)
    Replies: 4
    Last Post: 08-26-2007, 03:30 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
  •