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  1. #11
    I expect over 90% to be between 2 and 3.


  2. #12
    GODOSIDIS's Avatar
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    Quote Originally Posted by Subtlesoldier View Post
    I expect over 90% to be between 2 and 3.
    And we all expect your theory..

  3. #13
    www.eastcoastpwc.net Scott's Avatar
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    Quote Originally Posted by GODOSIDIS View Post
    And we all expect your theory..
    I spoke with J on the phone about this. His theory makes complete sense. Ill let him come forward with his explanation.

    Chris,

    no cracked heads on your end?

  4. #14
    copy and paste from my site

    This is a theory not something that can be proven right or wrong:

    I was talking to Waz one night about the head cracking issue I think several months ago and just some of the things we thought it could be. I dont think either one of us were convinced it was detonation or just detonation because to many were starting to turn up. Somewhere during the conversation we were talking about temperature and how the head should be regulated or would be better regulated. We discussed adding a thermostat but nothing more was ever said about it on this end.

    So day before yesterday I start looking at the flow path for cooling because I have an unnamed project brewing, I was looking at IC routing and trying to figure out how to cool the turbo or from where to get the water. Basically I was studying the drawing and then I saw something in the flow and thought "damn I bet that is causing the heads to crack"

    Look at the flow into the head and try and picture the temp difference as the water enters the head. One side feeds directly from the pump and the other goes through the stator and the oil cooler before entering the head. So the temp difference will vary greatly and probably more so the cooler the water is. Also, picture where the water enters the head and where the cracks are happening. I believe the head is under constant stress between cylinder 2 and 3. This stress is not catastrophic but it is enough to eventually crack the head. At least that is my theory for now.

    I expect the data to support this also, but I dont know for sure. It may just be poor casting I have no clue and I am just suggesting this. Thanks to Waz for planting the idea about temp and unregulated temps. Hell, maybe he already thought of this and I just didnt catch it till a couple of days ago.

    So there are my thoughts. If true, this is an easy fix. Just equalize the temp as it enters the head or preheat it I should say. Then there is always the fact after shutoff you are hitting a hot piece of aluminum with cool water everytime you start, but the same thing happens with a 15f.

    If I remember correctly the 15f enters from the center and does not dual feed or at least the mixture combines before entering the head. That is why I want to see a 15f head to confirm. I cant see my lx head as it sits in the hull.



    So possible choices are a log that combines the two sides then splits and feeds the head.

    Remove the stator to oil cooler line and let that feed one side and let the oil cooler be only on the other line

    or come up with your own way. Like I said this is a theory. Remember this the colder the water you ride in the greater the heat transfer and the greater the temp difference is going in to the two sides.

    I didnt see where the two sides on the 250 were connected. At least I could not get light to shine through.

  5. #15
    Interesting and well thought out. If you look closely at the Pic Scott provide in Post Number 6 you can see he is not running the PMR9B spark plug. Looks like a CR9EK. Many have said here the KAWs tend to run a little on the hot side anyway (by inherent design). Do PMR9B's run cooler? If this is so could be an easy way to lower head temps???

  6. #16
    Take the time to smile sirbreaksalot's Avatar
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    Quote Originally Posted by Subtlesoldier View Post
    copy and paste from my site

    This is a theory not something that can be proven right or wrong:

    I was talking to Waz one night about the head cracking issue I think several months ago and just some of the things we thought it could be. I dont think either one of us were convinced it was detonation or just detonation because to many were starting to turn up. Somewhere during the conversation we were talking about temperature and how the head should be regulated or would be better regulated. We discussed adding a thermostat but nothing more was ever said about it on this end.

    So day before yesterday I start looking at the flow path for cooling because I have an unnamed project brewing, I was looking at IC routing and trying to figure out how to cool the turbo or from where to get the water. Basically I was studying the drawing and then I saw something in the flow and thought "damn I bet that is causing the heads to crack"

    Look at the flow into the head and try and picture the temp difference as the water enters the head. One side feeds directly from the pump and the other goes through the stator and the oil cooler before entering the head. So the temp difference will vary greatly and probably more so the cooler the water is. Also, picture where the water enters the head and where the cracks are happening. I believe the head is under constant stress between cylinder 2 and 3. This stress is not catastrophic but it is enough to eventually crack the head. At least that is my theory for now.

    I expect the data to support this also, but I dont know for sure. It may just be poor casting I have no clue and I am just suggesting this. Thanks to Waz for planting the idea about temp and unregulated temps. Hell, maybe he already thought of this and I just didnt catch it till a couple of days ago.

    So there are my thoughts. If true, this is an easy fix. Just equalize the temp as it enters the head or preheat it I should say. Then there is always the fact after shutoff you are hitting a hot piece of aluminum with cool water everytime you start, but the same thing happens with a 15f.

    If I remember correctly the 15f enters from the center and does not dual feed or at least the mixture combines before entering the head. That is why I want to see a 15f head to confirm. I cant see my lx head as it sits in the hull.



    So possible choices are a log that combines the two sides then splits and feeds the head.

    Remove the stator to oil cooler line and let that feed one side and let the oil cooler be only on the other line

    or come up with your own way. Like I said this is a theory. Remember this the colder the water you ride in the greater the heat transfer and the greater the temp difference is going in to the two sides.

    I didnt see where the two sides on the 250 were connected. At least I could not get light to shine through.
    Hey this theory works for me anyway
    and I know of at least 1 other crazy scientist as well

    Just imagine you being the heat soaked alloy cylinder head after a 5 min WOT run.
    You pull up and chat or have a 5 min break ( more heat soak with NO water supply)
    then you start the ski and tip freezing cold water onto the lovely hot alloy material

    Personally after being in the automotive mechanical field (for 24yr's)
    would say that this type of rapid tempreture cycling will only lead to cold cracking !!

    hey cars run thermostats for a reason .... Why
    to maintain a internal temperature to promote less wear and durability

    what do we do every time we stop and then restart.

    tip cold water on the stinking hot cylinder head..makes not so good sence to me

    I have a inline remote Thermostat I want to play with on my ski one day
    (it a GANN product )I use them on cars at work for other reasons
    fits on the exit water hose and controls water flow, if the water is too cold it closes


    If this theory is remotely true ,boy racers or just people that do a lot of wot-stop -sit- restart riding could see the most cracking ( possibly the colder water seasons could in crease cracking head )

    I dont believe the different cylinder temperature from a different plug has any affect on it
    not saying impossible , just to me the cold water theory/water flow is a bigger potential issue

    anyway I am going back to my lab to make more home brew :yay2:

  7. #17
    Moderator DrewNJ's Avatar
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    Interesting read guys..

    So my first thought would be what about moving the cooling for the output shaft cover to the other cooling feed line to the head?

    So one feed line would go to the oil cooler then the head and the other cooling line would go to the output cover then to the head. Dunno how much heat is in that cover though...

  8. #18
    www.eastcoastpwc.net Scott's Avatar
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    Re: 250/260 heads cracking

    Quote Originally Posted by john belton
    Interesting and well thought out. If you look closely at the Pic Scott provide in Post Number 6 you can see he is not running the PMR9B spark plug. Looks like a CR9EK. Many have said here the KAWs tend to run a little on the hot side anyway (by inherent design). Do PMR9B's run cooler? If this is so could be an easy way to lower head temps???
    Man your good. Your 100% correct

    Sent from my iPhone using Tapatalk

  9. #19
    JET250's Avatar
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    just like any high performance athlete, you should have a warm up and cool down period.

  10. #20
    Quote Originally Posted by Subtlesoldier View Post
    copy and paste from my site

    This is a theory not something that can be proven right or wrong:

    I was talking to Waz one night about the head cracking issue I think several months ago and just some of the things we thought it could be. I dont think either one of us were convinced it was detonation or just detonation because to many were starting to turn up. Somewhere during the conversation we were talking about temperature and how the head should be regulated or would be better regulated. We discussed adding a thermostat but nothing more was ever said about it on this end.

    So day before yesterday I start looking at the flow path for cooling because I have an unnamed project brewing, I was looking at IC routing and trying to figure out how to cool the turbo or from where to get the water. Basically I was studying the drawing and then I saw something in the flow and thought "damn I bet that is causing the heads to crack"

    Look at the flow into the head and try and picture the temp difference as the water enters the head. One side feeds directly from the pump and the other goes through the stator and the oil cooler before entering the head. So the temp difference will vary greatly and probably more so the cooler the water is. Also, picture where the water enters the head and where the cracks are happening. I believe the head is under constant stress between cylinder 2 and 3. This stress is not catastrophic but it is enough to eventually crack the head. At least that is my theory for now.

    I expect the data to support this also, but I dont know for sure. It may just be poor casting I have no clue and I am just suggesting this. Thanks to Waz for planting the idea about temp and unregulated temps. Hell, maybe he already thought of this and I just didnt catch it till a couple of days ago.

    So there are my thoughts. If true, this is an easy fix. Just equalize the temp as it enters the head or preheat it I should say. Then there is always the fact after shutoff you are hitting a hot piece of aluminum with cool water everytime you start, but the same thing happens with a 15f.

    If I remember correctly the 15f enters from the center and does not dual feed or at least the mixture combines before entering the head. That is why I want to see a 15f head to confirm. I cant see my lx head as it sits in the hull.



    So possible choices are a log that combines the two sides then splits and feeds the head.

    Remove the stator to oil cooler line and let that feed one side and let the oil cooler be only on the other line

    or come up with your own way. Like I said this is a theory. Remember this the colder the water you ride in the greater the heat transfer and the greater the temp difference is going in to the two sides.

    I didnt see where the two sides on the 250 were connected. At least I could not get light to shine through.

    15F head has water feed coming from the Intake side . It travels through the head and exits out the exhaust.

    I'm letting another one of my cooling secrets out. Did it last year on our stock race boat that was seeing Oil temps of 270.

    Since we found oil cooling problem we have rerouted our cooling. I never thought of it that way in referance to preheated as you said but we did it to give the oil cooler fresh cool water and to balance temps entering the cooling bar of the head. Never really thought of it as a fix for cracking heads though we havnt seen them since.

    We do this by running the line that usually goes into the magneto cover to reroute to directly from the pump to the oil cooler then onto the head.

    We then reroute the one that did go to the rear of head to now route through the magneto cover first then to the rear of the head. Just as Drew had mensioned

    I dont have Motec configured to monitor this single event. I do though know that none of the temps changed in the engine other then oil it self. Didn't make it run any better but it seems to help with oil temps dropped a bit. Cant say its a cure for head problems as it dont do anything for stop and restarts.

    Not actually sure people should go and follow what I'm doing but at least we are trying it and so far so good. Your theory is a strong.

    Some picks.
    Red arow in is hot water from Mag/Oil water line.
    Blue is straight from the pump.
    Click image for larger version. 

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    Water into the head then flows down the cylinder and out the side outlet by Supercharger to the water waterbox. Water also flows out the exhuast and from top of pipe out the pump box.

    Here is your Intake and exhuast cooling of a 15F Notice the one lin out, it goes to waterbox.
    Click image for larger version. 

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    Click image for larger version. 

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    The cooling bar can also be done on the 250. Just needs to be bore out. and tapped.

    Here right at these points. Ive drilled a bad head but never routed through this point.

    Click image for larger version. 

Name:	Tap cooling..JPG 
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