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    Need Help With Cooling Options
    #1
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    I completely tore down my 1990 Ski Doo Safari LX 447 fan snowmobile this weekend after a buddy melted down the left piston. We are contemplating purchasing a new cylinder and piston, but don't want it to overheat again. What are any possible options for getting it to run cooler? We already want to make the mixture richer with different jets, and we want to add a temp gauge and possibly add an electric fan in addition to the crank driven one already on the motor. Any and all thoughts, comments, and help appreciated on any of this
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    Re: Need Help With Cooling Options
    #2
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    I am assuming 2 stroke here... back in the day when all there was was air cooled birt bikes, quads, 3 wheelers etc there wasnt much that could be done other than let it cool off every now and then. Synthetics oils will help some.
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    Re: Need Help With Cooling Options
    #3
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    Yes, two stroke. So there's nothing that can be done to help it?
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    Re: Need Help With Cooling Options
    #4
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    Oil Injection or Premix?
    My first buggy was powered with a Kawasaki two stroke twin. It was intended to be an ultralight engine. Built in belt driven fan and shrouding.
    On the first trip out I burned a hole through the piston just like you did.
    I did 3 things.
    1. Increased Jet size.
    2. Switched oils from some synthetic 100:1 mix to Yamalube R at 32:1
    3 Installed a cylinder head temp gage to keep an eye on things.

    Car never holed a piston again.
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    Re: Need Help With Cooling Options
    #5
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    It's oil injected. So we will up the jet size and install a cylinder head temp gauge. It didn't necessarily burn a hole Through the piston, just took lots of particles from the top exhaust side and dispersed them throughout the cylinder and exhaust pipe lol not that it makes any difference. But either way, thank you for your help it is much appreciated
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    Re: Need Help With Cooling Options
    #6
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    Pic?
    But an elec fan in front of engine would help I think.
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    Re: Need Help With Cooling Options
    #7
    Millenium Member nutz4sand's Avatar
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    One other thing you can consider Bob is the fuel. If you are just buying gas anywhere at any old gas station it will likely have ethanol in it. If it does this makes it run a lot leaner in a two stroke. If you jet it to run good on regular gas and then get some with ethanol it will automatically run leaner and hotter and can cause issues (even with a single cylinder, even liquid cooled, ethanol can suck....).

    Another problem with ethanol is its never the same twice. Sometime buying it from the same pump it's more or less. Guess what. Gotta jet for it each tank.... Fun eh?

    Or you can buy race gas ($$$$) but safer to jet to run hard. You can also often get gas at Marinas where boats do as it often does not have any ethanol. Some automotive street corner gas stations also sell gas with no ethanol in it. Gotta ask and do some research. I would not trust the guy or gal behind the counter to know!!!!!! Gotta check deeper than that!

    I have one two stroke left with carbs and any sled two stroke I would ever use again would HAVE to be fuel injected. The F.I. systems can deal with the ethanol as they adjust on the fly. But I would still avoid ethanol if I could.

    With ethanol fuel in a carbed two stroke you have to jet it so rich to survive the variances that it will not have the good old two stroke power hit but soggy old fourstroke power (old as in old days fourstroke not new power fourstroke stuff) and still need a lot of spare spark plugs as they tend to foul out. Sucks eh?

    Also just to be sure you need to do a "crankcase pressure test" (both negative and positive) on both cylinders (Not a compression test but those are needed too) If you have a tiny air leak it will also lean out the cylinder and melt the piston no matter what unless you are running MEGA rich already.

    I have had bad bearing seals, bad gaskets, porus metal in the cylinder passages and even a cracked phenolic (type of plastic I am spelling it wrong I think) carb spacer cause a lean condition too. Only way to find these is a good inspection but more-so a crankcase pressure test. Easy and pretty cheap to do. Should be a regular part of any two stroke maintenace and will often save you good money in return. If you do not know how to do these we have a tutorial on this site buried somewhere! :]

    One thing I NEVER do is assume when a two stroke melts a piston. It may be jetting. But until you check for crankcase leaks your just guessing.


    Many times I have seen guys burn down a piston. Hone or bore the cylinder and buy a new piston/rings and gaskets. Slap it together only to ruin the new piston in minutes because the leak in the crankcase "zone" is still there and its too dam lean.
    Now that NOBAMA has PROVEN he is the absolute WORST president in the history of history Jimmy Carter can thank him for stealing the dunce crown.

    Lets hope the next guy repeals NObama care along with the rest of the stupid crap this blight on our windshield has done.
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    Re: Need Help With Cooling Options
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    Millenium Member nutz4sand's Avatar
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    I will also add that I think that sled engine only had one carb. I have seen guys with twin fan air cooled with dual carbs actually run a tad richer jet on the left side away from the fan as that cylinder gets the warm air from the first nearest the fan and runs hotter due to this. Not worth worrying about if you do not already have dual carbs.
    Now that NOBAMA has PROVEN he is the absolute WORST president in the history of history Jimmy Carter can thank him for stealing the dunce crown.

    Lets hope the next guy repeals NObama care along with the rest of the stupid crap this blight on our windshield has done.
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    Re: Need Help With Cooling Options
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    It actually is a dual carb, and that makes sense but I haven't checked jet sizes yet. If someone could tell me how to do the pressure test, that would be a good thing to do it sounds like. And Carl, what were you looking for pictures of? The melted piston and cylinder? The whole engine and setup? Pics of both are on my build thread, but if you'd like I could post a few here. Again, thanks for all the help.
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    Re: Need Help With Cooling Options
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    Oh and we are also considering a whole new engine from a different snowmobile if that option proves cheaper. It will cost around $300 for two cylinders, pistons, rings and bearings, and we might be able to find a whole motor or sled for that much on Craigslist somewhere. Just keeping our options open
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