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  1. #21
    they sure as shit had ecu and electrical problems that would render them useless or event totaled at $1300 an ecu ...

    Quote Originally Posted by cjk6119 View Post
    The problems with Yamaha heads cracking, is that just related to the supercharged engines or both, naturally aspirated and supercharged are having problems with their heads?

    Engines that are detonating will tend to overheat, because the boundary layer of gases gets interrupted against the cylinder head and heat gets transferred from the combustion chamber into the cylinder head. This might be from not using the correct octane level.

    You know what's interesting here is, when Honda had a ski on the market it seemed to be problem free for the most part. They did not have a pattern of heads cracking, clutches breaking down and they ran a turbo chargers on their engines, and for the most part was trouble free with that setup. It looked to be a very reliable platform to build on.

    CJ

  2. #22
    dcuhpw's Avatar
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    Quote Originally Posted by big john View Post
    IMO the most likely cause is shutting the motor off after a hard hot run without allowing it to cool off by letting it idle around for a few minutes, or restarting a hot motor and blasting it with cold water. water does circulate thru the head before the thermostat opens, but when it reaches temp it allows maximum water flow to cool the motor. ive always idled/low rpm for a couple minutes to bring the engines down after a hot run, almost 300 hours between two ski and no cracked heads. remember that the motor drains out when its not running and that head is hot af with nothing in it to absorb the heat. everyone know not to pour cold water into a hot engine
    YES, I completely agree. Older kawi ultras have the same issue. Interestingly enough, here on Guam were water temps never dip below about 82 there have been no reports of cracked heads from either the Yami or Kawi dealerships (I know the lead techs).

  3. #23
    Hmmm yea here in seabrook when I ride the water is 75 for a couple of weeks then goes to 80+ and I don’t hear about many heads cracking.

  4. #24
    John F.'s Avatar
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    Quote Originally Posted by seabrook View Post
    Hmmm yea here in seabrook when I ride the water is 75 for a couple of weeks then goes to 80+ and I don’t hear about many heads cracking.
    I ride in the same area as you and have had 3 heads crack and my friend I ride with has had at least 1 head crack as well.
    We both do proper warm up and cool down of the skis and monitor engine temps.
    I believe there is a of casting flaw in some of these heads.

  5. #25
    Quote Originally Posted by John F. View Post
    I ride in the same area as you and have had 3 heads crack and my friend I ride with has had at least 1 head crack as well.
    We both do proper warm up and cool down of the skis and monitor engine temps.
    I believe there is a of casting flaw in some of these heads.
    I'm on the casting flaw train. I ride I the same area as speeder and have had my fzr since 2009 and running 15psi boost since 2012. The only wild card is my heavily modded cooling system. I keep things running really quite cool.


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