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  1. #1

    Replacing crank seals for the first time.

    Found a small air leak in front cranks seal so I decided to replace all seals and base gasket. I have been doing my own maintenance for years, rebuilt carbs, and jet pumps but never split cases so this is new to me. Attached is some pictures of what I have seen. Any comments or concerns? Engine was running ok except for the occasional running away on the trailer which is the reason I thought there was an air leak.
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  2. #2
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  3. #3
    gp1200270's Avatar
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    Hard to tell by the pics.Everything looks ok but the questions I would go through.
    1.did you check compression before you pulled it?
    2.why did you blow the front seal.
    3.how many hours on the motor.
    4.when was the last time the carbs were rebuilt/cleaned out.

    I have replaced seals all around on a few of my skis.Just take your time and make sure the seals go in the same way as the old ones.Clean,rebuild carbs,check all of your wiring.I did have my rear seal blow one time due to a leak in one of my carb needle.Hope this helps you out.

  4. #4
    Myself's Avatar
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    Make sure there is no up and down play in the rod bearings. You should also hone those cylinders and put on some new rings as I can see the blow-by on the piston skirts. Common on an older engine that's never been rebuilt. Piston wash pattern looks great. Go ahead and clean/inspect carbs but maintain the exact settings you have now. When you re-assemble the bottom end with 3-bond or Yama-bond sealant you should also smear a little around the areas the seals lay in. It helps keep them glued in place during a backfire should you ever have one. Now would also be a great time right before honing to clean up Yamahas terrible sleeve to cylinder port matching and chamfer the port edges.

  5. #5
    Thank you both for the great advise. The last time I checked the compression was winter of 2012, I did not run the ski at all this past summer because I knew I had to rebuild the intermediate housing and I knew I was developing an air leak somewhere. The only one i found was a small seep from the mag crank seal. I want to say that the reading i got were 108M, 110C, 110P. I last rebuilt carbs 3 seasons ago. So far this winter I have rebuilt pump, rebuilt intermediate housing, sealed pump shoe with kit, done Oside Bill's drill out return mod, and removed cleaned gas tank.
    I have new mikuni kits, N&S's, and rings on the way. Engine has 120 hours, it was showing small signs of an air leak so that's why I took it apart. I also think it is possible that the carb base gaskets and or intake gasket was leaking as I reused everything when I rebuilt carbs 3 years ago.
    I have a few other questions, 1. Can i hone the cylinder myself? What do i need? 2. Do I need to clean up the pistons? If so how and with what? 3. I left the head on the cylinder when I split the cases, what are your thoughts on not replacing head gasket if I didnt remove the head?4. I assembled the cases a few days ago but used waaaay too much 3 bond, so I split cases again to clean everything up again. Can I reuse the new crank seals? or do i have to buy new ones again. OEM is what I had purchased.

  6. #6
    Myself's Avatar
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    Yes, just re-use your new seals. The excessive sealant wouldn't have hurt anything. A utility blade held perpendicular to the piston tops and used with a scraping motion will clean all the carbon off BUT the ring grooves will also need cleaned out after that too. Are you putting in new rings?.....you should. The head needs to come off and gasket replaced. Those cylinders need to be honed and it cant be done with the head on. You should be able to stop by any auto, motorcycle, or mower repair shop and give somebody a $20 to hone those for you. Or spend the $20 on a hone from Auto Zone and watch a couple Youtube vids on how to do it yourself.

  7. #7
    Yes i have new rings, what's the best method to clean the ring grooves? I have a friend from work that is suuuuper picky and is a great mechanic that said he will hone cylinders for me. I have seen his work and completely trust him. Thank you for talking me into honing. Now just need to buy a new head gasket and that that wierd looing oring type gasket.

  8. #8
    What is the best method to clean up pistons?

  9. #9
    Myself's Avatar
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    I use a utility blade held perpendicular to the piston top and scrape all the carbon off. Then i use a fine wire wheel to finish. I use a piece of 220 grit wet sandpaper folded over to clean out the ring grooves. Finally give it all a good bath and blow dry with compressed air.

  10. #10
    Good bath in water? I'm guessing the pistons are not steel?

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