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  1. #1

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    650sx cooling routing

    Hey, I have read a bunch of posts on this forum so I finaly decided I should become a member.

    I have had a 650sx for a couple years so now I kind of want to modify it to get more power out of it. An easy mod that I've heard of is to fill in the hole between the water jacket and the exhaust in the headpipe with JB weld. Then drill it out to an eighth of an inch. This runs the exhaust drier and more efficiently supposodly. (Has anyone here done this before?)

    Thats all fine and good but I am just trying to figure out how the water flows through the engine. As far as I can figure it comes in from the pump to the exaust manifold, goes into the engine, out the top of the head, into the head pipe then out the pisser and into the exaust. The only problem is that the water jacket of the headpipe is connected to the waterjacket of the exaust manifold. Wouldnt water just flow in the manifold then out the head pipe? I am thinking that there is supposed to be a gasket that lets just exaust but not water flow from the exaust manifold into the head pipe. Maybe there is supposed to be this gasket and my ski is running super hot!

    How hot is the head supposed to get? If someone has a diagram that shows how the cooling hoses run that would be great. Also I would like to hear about how to further modify the stock exaust. Thanks.


  2. #2
    DPeteLand PeteSkeet's Avatar
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    Quote Originally Posted by Codenamecody View Post
    Hey, I have read a bunch of posts on this forum so I finaly decided I should become a member.

    I have had a 650sx for a couple years so now I kind of want to modify it to get more power out of it. An easy mod that I've heard of is to fill in the hole between the water jacket and the exhaust in the headpipe with JB weld. Then drill it out to an eighth of an inch. This runs the exhaust drier and more efficiently supposodly. (Has anyone here done this before?)

    Thats all fine and good but I am just trying to figure out how the water flows through the engine. As far as I can figure it comes in from the pump to the exaust manifold, goes into the engine, out the top of the head, into the head pipe then out the pisser and into the exaust. The only problem is that the water jacket of the headpipe is connected to the waterjacket of the exaust manifold. Wouldnt water just flow in the manifold then out the head pipe? I am thinking that there is supposed to be a gasket that lets just exaust but not water flow from the exaust manifold into the head pipe. Maybe there is supposed to be this gasket and my ski is running super hot!

    How hot is the head supposed to get? If someone has a diagram that shows how the cooling hoses run that would be great. Also I would like to hear about how to further modify the stock exaust. Thanks.


    should only be getting luke warm to warm... never hot.. if its getting hot i suggest dual cooling.

    theres a cool DIY on dual cooling on PWC today.. i can get you the link if you need it.

  3. #3
    DPeteLand PeteSkeet's Avatar
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    the head can get very hot.. i mean theres just a giant combusition going on underneath it =) ... dont worry about that... but remember:

    the cooler the engine *except in some performance ones* the better the engine runs along with efficiency... if you have a nice performance engine (for example european sports cars) they like to run hot to better burn their fuel and accept higher octane.

    your two cylinder two stroke engine is not yet it can and probably will get hot-very hot because it is primitive.. though cooling is never bad because we do not want it to overheat, seize, or cause any other problems like blown head gaskets

    hope that helped!



    -flyin p

  4. #4
    saf's Avatar
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    Quote Originally Posted by flyinpolak View Post
    the cooler the engine *except in some performance ones* the better the engine runs along with efficiency...

    your two cylinder two stroke engine is not yet it can and probably will get hot-very hot because it is primitive..
    hahaha primitive ?. There is nothing primitive about a 2 stroke, its a work of art, that doesnt rely on mechainical control of intake and exhaust timing like a 4 stroke. They are small and light, yet displacement wise can put a 4 stroke to shame !. And considering the 4 stroke is a older engine than the 2 ... id call that primitive.

    But the Q, no its not better if it runs cooler. Every engine has a mechaincal tollerance its built to, plus they are lubicated with oil, 4 strokes, 2 stokes and the rotary. This oil needs a running temprature, and will have side effects if it doesnt see it.

    Imgine cooking french fries in lukewarm oil ... wont work will it ?. A two stroke relies on heat to expand the bores, and considering that alum expands quicker than steel, the pistons will expand first and seize. This is called a cold seizure, and it doesnt have to happen only around startup.

    Unless your pushing compression and some timing/porting, you dont need dual cooling. But i would change the shithouse hose and clamp setup for push in SMC fittings and a true 8mm line. Do you have a bypass plumbed in ?.

    You should have a metal separation gasket between the ex manifold and the header, to stop the water bypassing the motor. Water comes into the ex manifold, flows around, then goes up to the cyl, flows around that, and then into the head, where it runs out and into the exhaust (stock), but you should also have another exit out the side known as a bypass (thats DIY).

  5. #5
    DPeteLand PeteSkeet's Avatar
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    Quote Originally Posted by saf View Post
    hahaha primitive ?. There is nothing primitive about a 2 stroke, its a work of art, that doesnt rely on mechainical control of intake and exhaust timing like a 4 stroke. They are small and light, yet displacement wise can put a 4 stroke to shame !. And considering the 4 stroke is a older engine than the 2 ... id call that primitive.

    But the Q, no its not better if it runs cooler. Every engine has a mechaincal tollerance its built to, plus they are lubicated with oil, 4 strokes, 2 stokes and the rotary. This oil needs a running temprature, and will have side effects if it doesnt see it.

    Imgine cooking french fries in lukewarm oil ... wont work will it ?. A two stroke relies on heat to expand the bores, and considering that alum expands quicker than steel, the pistons will expand first and seize. This is called a cold seizure, and it doesnt have to happen only around startup.

    Unless your pushing compression and some timing/porting, you dont need dual cooling. But i would change the shithouse hose and clamp setup for push in SMC fittings and a true 8mm line. Do you have a bypass plumbed in ?.

    You should have a metal separation gasket between the ex manifold and the header, to stop the water bypassing the motor. Water comes into the ex manifold, flows around, then goes up to the cyl, flows around that, and then into the head, where it runs out and into the exhaust (stock), but you should also have another exit out the side known as a bypass (thats DIY).


    i did state if it is running very hot he should do dual cooling not warm... and agreed on the other parts.. i am quite aware of the side effects of having an engine run too cold... and yes oil does need to be heated in order to work properly.. i still feel that two strokes are primative because they are so easy a 10 year old can fix one if he had the muscle to remove some of the bolts. not that they are crappy... i dont own a four stroke.. my entire fleet of skis is two stroke... and i will keep it that way till laws and regulations make me change it.

  6. #6
    saf's Avatar
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    Quote Originally Posted by flyinpolak View Post
    i did state if it is running very hot he should do dual cooling not warm...
    Sure i agree, but there must be a reason its running hot, and that needs to be addressed before more cooling is added.

    Quote Originally Posted by flyinpolak View Post
    i still feel that two strokes are primative because they are so easy a 10 year old can fix one
    Perhaps they can if they had guidance, but thre beauty of two strokes is that they are so simple they become extremly complicated, its easy to build a good motor, its much harder to build a great motor. Thats the rewards of two strokes ...

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    DPeteLand PeteSkeet's Avatar
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    Talking

    Quote Originally Posted by saf View Post
    Sure i agree, but there must be a reason its running hot, and that needs to be addressed before more cooling is added.



    Perhaps they can if they had guidance, but thre beauty of two strokes is that they are so simple they become extremly complicated, its easy to build a good motor, its much harder to build a great motor. Thats the rewards of two strokes ...



    agreed.... fully.

  8. #8

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    should only be getting luke warm to warm... never hot..
    I remember at one point in time when the water from the pole dripped on the head, it boiled. No joke.

    I am still running the dinky 28mm carb and I found somewhere that the high jet is supposed to be 5/8 turns out and the low is supposed to be 1 1/8 turns out. If it is running too lean it can overheat, are these the right settings?

    Sure i agree, but there must be a reason its running hot, and that needs to be addressed before more cooling is added.
    You should have a metal separation gasket between the ex manifold and the header, to stop the water bypassing the motor.
    I do not have said gasket. Where can I get one and is it safe to operate the engine as is?

    but you should also have another exit out the side known as a bypass (thats DIY)
    Please explain


    theres a cool DIY on dual cooling on PWC today.. i can get you the link if you need it.
    Yes I would greatly appreciate it.

    Thanks for all the help guys.

  9. #9

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    By the way, does anybody around here have any performance parts that they are willing to sell? I would like something to replace the 28mm carb and I really want a new pipe but $$$$. Also, recommendations for free/cheap performance upgrades that I can do my self are appreciated.

  10. #10
    saf's Avatar
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    Quote Originally Posted by Codenamecody View Post
    I do not have said gasket. Where can I get one and is it safe to operate the engine as is?
    There is your gasket, part number 11009. This pic is from Alljets website, the gasket was the same all years, but enter your year and you can snoop around and see what is where.

    http://216.37.204.206/alljet/Kawasak...ModelYear=1993


    As far as jetting your stocker, cant tell, been too long and honestly i dont know if ive ever even tuned one. Id just toss it for a new 44sbn Mikuni, to what you will also need a new inlet manifold, and a filter adaptor and a spark arrestor for you guys in the us that have to run them, something good like a TauCeti.

    Exhaust, look about .. a Factory Pipe is the best IMHO, anda nice waterbox, bump some comp into the head and your on the way of having a nice little ski that is nothing like the one you have now

    As far as a bypass, see in this pic ..


    You have the front of the head, there is a nipple/casting that goes nowhere ? ... well that one needs to be drilled and tapped (1/8npt) and a 3/8th line needs to go from there, straight out the side of the hull to a water outlet fitting.

    Optimally, you want to do this 180deg opposite from the original outlet (where part 92005 goes in) so in the back corner of that photo, somewhere behind the "KA" in Kawasaki, as that will draw water to and around the back cyl, stop it being stagnent so to speak.

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