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Thread: So I Am Flying Down The River And Become A Flaming Comet...

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    Default So I Am Flying Down The River And Become A Flaming Comet...

    Yuh-huh! It happened to me. Really. Today.

    Driving down to Napakiak, doing about 45 mph, on the river, about 2-inches of hard snow so minimal resistance to forward movement. Just groovin' bey-beh...and what are all those flames shooting out of the hood!!!

    Slam on the brake as I reached for the ignition to turn off (thought it might be electrical), jump off, throw the backpack clear (thought it might be a broken fuel line), open the hood and see the flames are all around the front of the muffler. Begin throwing snow on them as quickly as I can humanly scoop and see them disappear pretty quickly. Also put the flame out on the hood (it was on fire too).

    Looks like the Arctic Cat briefcase-sized muffler got too hot and radiated heat melted, then caught the plastic bellypan on fire. It was an interesting 20 seconds of my life I tell you what! While I was unlatching the hood to get it open, I actually thought to myself, "well at least I have full coverage insurance". Kind of odd the things that go through ones mind during a crisis.

    So now to the shop in the morning to find out what to do about this. I am going to cut away all the plastic from that area, and rivet in thin aluminum in which I have drilled lots of 3/8" holes to allow airflow around the muffler. I'll do the same along the bottom of the pan and install a sheet to protect the side of the hood area from radiated heat.

    While driving back from Napakiak, I had both feet on the bulkhead to hold the hood up as it had buckled from the heat and wanted to lay on the stinger coming off the expansion chamber. I was able to watch the stinger and front half of the muffler start to glow dull red, through orange and into yellow within the space of 10 seconds or so when I stayed between 20-25 mph. At first I didn't even believe what I was seeing until I stopped to shut down the motor and let everything cool for a few minutes. Then I did the same thing again. After this I experimented finding I could keep the pipe cool as long as I was about 30 mph. Anything above 35mph and the pipe would not become incandescent. Pretty crazy. For some reason as yet unknown, at low speeds/engine rpm's/carb opening, quite a bit of gas is getting into the motor and burning very late in the pipe/muffler.

    More to come.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    Member Dupont Spinner's Avatar
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    What sled???? Check plugs and color. It sounds like you may need to move your needles up some....maybe a change in the pilot jet. Carbs recently cleaned? Water? Snow Dust?

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    I checked when I bought the sled, jetted fat from the factory (aren't they all?), but since it was -22*F outside, I don't think it would be the jets.
    My next door neighbor who is a snogo mechanic told me it sounded perfect when driving up the street. I can tell you there is no burbling when idling or slow going, even when warming up I can barely smell gas, unlike when it is really warm, say +20*F. So it is a mystery. Oh, I had it in the shop before Thanksgiving for a complete top-to-bottom, front to back check-up and tune-up.
    I will check the plug color but don't know that will tell me too much as I didn't get the machine into powder or haul it up to WOT for a mile or so. I will check anyway, at least it will tell me how the motor is doing at slow speeds.

    Oh, 2007 Arctic Cat 570 Bearcat fan-cooled with 34 mm Mikuni round-slides.

    New hood with decals is $644.00, w/o decals $600-ish. The melted LH side panel/belly is $87.00.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    After you put the fire out and cooled things down, how did it start? Was it easy or seemed flooded? Just seems like you must have been getting too much unburnt fuel going into the pipe and cooking off. Once you got up to 35mph the motor may have been using the fuel that it was getting in the motor instead of the exhaust. Could be a sticky needle. Would pull the carbs and dig into them.

    On the cowling, you don't need the decals. They just add weight that will slow ya down!

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    Supporting Member iofthetaiga's Avatar
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    Maybe I would lose a lot of money on this bet, but I'm going to guess you don't find anything wrong with it. I'm going to bet it was a freak occurrence, and that you've got water in your gas that caused icing in a carb and froze a needle open.

    PS: I vote no decals too. But have somebody paint some flames on the new one...
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    Quote Originally Posted by alaskabliss View Post
    After you put the fire out and cooled things down, how did it start? Was it easy or seemed flooded? Just seems like you must have been getting too much unburnt fuel going into the pipe and cooking off. Once you got up to 35mph the motor may have been using the fuel that it was getting in the motor instead of the exhaust. Could be a sticky needle. Would pull the carbs and dig into them.

    On the cowling, you don't need the decals. They just add weight that will slow ya down!
    Fired right up. When I was going back up to Bethel I shut it down four times to cool. Each time dropped off, no backfire in the pipe, nothing. Fired right up again.

    Quote Originally Posted by iofthetaiga View Post
    Maybe I would lose a lot of money on this bet, but I'm going to guess you don't find anything wrong with it. I'm going to bet it was a freak occurrence, and that you've got water in your gas that caused icing in a carb and froze a needle open.

    PS: I vote no decals too. But have somebody paint some flames on the new one...
    Yeah I dunno. I like the flame idea! That would be too close to the truth though...
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    You can piddle with the puppies, or run with the wolves...

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Nitroman View Post
    Fired right up. When I was going back up to Bethel I shut it down four times to cool. Each time dropped off, no backfire in the pipe, nothing. Fired right up again.



    Yeah I dunno.
    It was a WAG. I've had some pretty weird anomalous icing with the GF's 340 in extreme temps. Seems like with your cycling it, you should have got enough warming of the carbs to remove any icing issue, but who knows? Only one way to find out.... Will be interesting to hear what you find with the plugs and carb innards.
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
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    Member Dupont Spinner's Avatar
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    Ok there are a couple of things....check your "Y" pipe mounting surface, exhaust donuts and your pipe for a crack. I seen you posted left side lower, are you talking clutch side? Check the muffler also, take it out and turn it upside down, baffles may have fallen or broke loose inside. When you reassembly the exhaust put hi temp rtv on all the joints to seal them tight. What about the exhaust shield and insulation?

    The pipe has to get hot for a 2 stroke to work but things will start to glow over 1500 degrees. So at that point you are going to start hurting that engine....long before you melt the hood. That is the reason to check plugs for alunimum specs/coloring. With it restarting with ease I doubt that is the case. So now need to find why the lean condition at the pipe.

    On EDIT: Does this thing have a pipe sensor???? If it does change it.

    Seen your post on the other site, will be interesting to see what is said.

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    Quote Originally Posted by Dupont Spinner View Post
    Ok there are a couple of things....check your "Y" pipe mounting surface, exhaust donuts and your pipe for a crack. I seen you posted left side lower, are you talking clutch side? Check the muffler also, take it out and turn it upside down, baffles may have fallen or broke loose inside. When you reassembly the exhaust put hi temp rtv on all the joints to seal them tight. What about the exhaust shield and insulation?

    The pipe has to get hot for a 2 stroke to work but things will start to glow over 1500 degrees. So at that point you are going to start hurting that engine....long before you melt the hood. That is the reason to check plugs for alunimum specs/coloring. With it restarting with ease I doubt that is the case. So now need to find why the lean condition at the pipe.

    On EDIT: Does this thing have a pipe sensor???? If it does change it.

    Seen your post on the other site, will be interesting to see what is said.
    Interesting your note on the donuts at the Y pipe. I saw some exhaust flow from that before the machine warmed up. This is a good idea. I think I will change that and get new springs while I'm at it.
    When I meant the LH side, on the AC parts websites, it lists that side as LH, so when you face the machine...
    It was the area right in front of the muffler. I will pull that tomorrow and check up in there as you suggest.
    No sensor on this pipe, I have taken it off before. The shields and insulation are good.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    You can piddle with the puppies, or run with the wolves...

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    If you're taking bets, I'll bet 33 cents it was due to removing those coins from inside the airbox! Perhaps those coins were placed there by the manufacturer (in a precise ratio of quarters, nickels and pennies) to regulate the airflow. So although they seemed like small change, removing them must've affected the economy of the airbox, right?
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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Seraphina View Post
    If you're taking bets, I'll bet 33 cents it was due to removing those coins from inside the airbox! Perhaps those coins were placed there by the manufacturer (in a precise ratio of quarters, nickels and pennies) to regulate the airflow. So although they seemed like small change, removing them must've affected the economy of the airbox, right?
    Well, yea, if he took the coins out of the air box, that would change everything! And I would then have to retract my previous WAG. But how do you know he took the coins out of the air box? Are you privy to inside information? I don't see where he said that. There's something fishy going on here. This doesn't add up.














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    I may be privy to imaginary secrets, but in this case I got my inside info from the flaming comet rider himself:
    http://forums.outdoorsdirectory.com/...ith-For-Repair
    Inspiration is simply the momentary cessation of stupidity.

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    Member Dupont Spinner's Avatar
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    3706-028 is the lower right belly panel where the exhaust sits. By the way good prices on the parts for new.

    Ok so it was cherry right at the stinger.......look in the muffler. If you were over-fueling that thing would run like do do. I think you were just running lean in the exhaust.

    Think of the mixture like an oxy acetelene torch, acetelene being the fuel buy it self it's a rich mixture and burns at a low temp. Add 02 and you lean out the mixture and it burns hotter. As your exhaust was exiting I believe it was picking up extra air from a bad gasket bringing your pipes temps up. Already at -24 you are at about the bottom temps for the factory settings, even starting fat.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Seraphina View Post
    I may be privy to imaginary secrets, but in this case I got my inside info from the flaming comet rider himself:
    http://forums.outdoorsdirectory.com/...ith-For-Repair
    The coinage post was FUNNY; worth it's weight in gold....but it turns out there was some critical info excluded from this thread. In the other thread Seraphina referenced it says you installed a Holtzmann ATACC on this thing recently........
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
    I would rather have a mind opened by wonder than one closed by belief. ~Gerry Spence
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    Supporting Member iofthetaiga's Avatar
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    So, seriously, Dupont Spinner of course knows what he's talking about, and I was thinking completely bass ackwards. I'll blame the beers, although that's a lame excuse. If your EGT is too high, you're running lean, not rich. And if you just installed the Holtzmann ATACC gizmo on this machine two weeks ago, and now your mixture is out of whack; well, you should know where to look first, eh?
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
    I would rather have a mind opened by wonder than one closed by belief. ~Gerry Spence
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    Supporting Member iofthetaiga's Avatar
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    ....And if you got the EGT high enough to nuke your exhaust pipe and set the cowling on fire, we shudder to think what the inside of your cylinders look like. Pull your spark plugs; keep track of which one belongs to which cylinder. Examine each one very closely for any tiny beads of aluminum spatter on either, or both. If you see any aluminum, the odds are good you'll be looking at rebuilding more than just a burned cowling. If you don't see any aluminum, then run a compression check. If that checks out good, put a shot of injector oil in each cylinder like you would when prepping it for summer storage, and pull it through slowly a couple times with the ignition off. Replace your fried plugs with new, properly gaped ones. Don't run it anymore with that aftermarket gizmo on it.
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
    I would rather have a mind opened by wonder than one closed by belief. ~Gerry Spence
    The last thing Alaska needs is another bigot. ~member Catch It
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    Dupont is correct about mixture. Lean would make it hot. Fuel cools.
    you did excluding the most important piece of info. Those can be a pain and have caused many of melted piston if not installed properly. Start your search there, as soon as you know you didn't melt your pistons.

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    It sounds like midrange lean to me. That means the needle clip needs to be lowered. At least that's the first place I'd look. Somebody probably raised the clip last spring when it was warm.

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    Rich makes it cool, lean makes it hot...in the engine. Unburned fuel (rich condition) can flow out of the engine into the pipe and ignite within the exhaust system, but I've never seen fuel burning in the exhaust cause any part of the exhaust to get any hotter than when the sled is running. In the dark I have seen fires inside the exhaust of my kid's Indy Lites after they have shut them off.

    Are your hood vents closed off? I know the newer 570's cannot handle any of their vent hoods being closed or the heat buildup causes melt downs like you had.

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    I spoke to Holtzmann back when I put on the ATACC on my xcr800. It does regulate the fuel levels in the carb bowls. If anything goes wrong, like a blockage, or one of the hoses falling off, the unit no longer is able to regulate fuel level so it is as if the ATACC weren't installed. In other words, it will never lean out the machine too much.

    Installation is really easy, once the installer know where to place the "air inlet". The Polaris has airbox carb venting, or, the vents on the carbs plug into the little nipples on the airbox, so you have to install the air inlet inside the airbox.

    Arctic Cat has the carb vents just pointing downwards. So the air inlet has to be outside the box. I have mine outside the box. I thought of this the very first thing as I was standing on the river next to my machine wondering if this would cause the muff to get hot. I can check by simply removing the vacuum line from the carbs. The machine should run much richer instantly. Oh, and here is a little tip: the instructions call for the vacuum source line to be between 16" and 24" in length. Holtzmann told me the longer line is leaner, the shorter line would run richer. I have mine cut to 20" exactly.

    If interested go here: http://www.holtzmaneng.com/ go to the left side of the page and look for ATACC, then read the installation instructions. The units really do work and save a bunch of time when you aren't always having to switch jets.

    Okay. First to take off the muffler and shake it good to see if the baffles have fallen/rusted/or somehow been damaged; I'll look up there with a flashlight too. I will see if the local shop has an exhaust donut (Grafoil compression washer I think they are called), and I'll get new springs. Besides cutting away all the plastic.

    It is still dark here, but I will take pix when my wife arrives from Napakiak. She has the camera.

    As for the coins being removed...at least I know why the machine isn't as snappy off idle. They must have been restricting the airflow to the carbs, so now I'm a little fat. This could be the reason for the lean condition. Just kidding.

    Last: I really do appreciate all the comments. I have this post over on Hardcoresledder, they are MUCH more into pure performance and as such I thought those hardcore types might have some insight. I have only had three hits, one of which the guy said mine isn't the first melted plastic 570 he's heard of, so this isn't uncommon. And the plastic bellypan is UHMW and only 3/8" from the muffler in spots.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

    Better living through chemistry (I'm a chemist)

    You can piddle with the puppies, or run with the wolves...

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