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  1. #1

    TX1200 Mmmm.....Toasty

    Picked up a blown 2002 TX1200 about a month ago, and have just gotten around to inspecting it. I have seen just about every known issue with Polaris machines at one time or another but this one has me scratching my head. The mag cylinder is seriously charred as seen in the pics. It has the tempo lines, and it's the final carb to receive fuel so my first thought is that this was caused by a lean condition resulting in catastrophic damage. But at the same time, I have never seen a cylinder that got so hot that it actually charred the paint on the carburetor on the side facing the cylinder. That thing must have been glowing! The PO claimed the temp light never came on, and also the P.L.A.N.E.T. exhaust baffles are intact and not melted through as they will do if the engine overheats. I haven't torn it down yet, but thought I'd throw this out there to see if anyone else has seen one get this hot on only one cylinder. The SBT "temperature dots" on the center and pto head covers are perfect.

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  2. #2
    Banned User
    Join Date
    Jun 2010
    Milwaukee WI
    Im going to guess a blockage in the cooling system on that cylinder did it. The overheat sensor is in the exhaust manifold so if just the one cylinder got hot it still wouldnt trip the overheat.

  3. #3
    kaotic1's Avatar
    Join Date
    Aug 2013
    I agree with BryanP, you could have a coolant blockage, probably in the bar on top of the heads. Did the engine lock- up sure looks like it should have... hopefully the crank and rod are ok and you can repair that jug and slug and be back in business.

  4. #4
    I was thinking the same as you guys, but it was strange that it was only the one cylinder on the one side. I finally tore it down tonight, only to find it was neither a lean issue nor a cooling issue.

    The engine was an SBT rebuild, so I had initially called them to find out if it was indeed under warrantee. They said it was shipped late 2011, and it was a warrantee replacement as the guy burnt up the first one. He had tried to get a third one but they wouldn't stand behind it.

    Upon taking it apart tonight I found the culprit. It was assembled without a head gasket O ring. It started using the leaking area as an exhaust port and eventually torched through the head and out into the water jacket resulting in the head cover and the outer cylinder taking the full heat from the combustion. It ruined the head as well as the cylinder, and of course it sucked in some water so the sleeve is rusted as well.

    I've read many horror stories about SBT, and honestly have never seen one of their rebuilds fail due to shoddy parts or workmanship. It's usually the mechanic who failed to correct the initial problem, such as gunked up carbs from Tempo lines, or clogged fuel filter, or something similar. This time however it was absolutely their fault. Additionally, if you look at the sides where the sleeve meets the cylinder housing, you can see where it's broken off like someone was using a hammer to install the sleeve.

    I have a complete engine out of a TXI I was going to throw in this one, but it looks like all I'm going to need is a 1.00mm OS cylinder, a head, and a set of rings. I'm hoping I don't have to replace the piston as I do know that different batches of pistons from SBT are different weights slightly and I'll have to tear down the other two to make sure they are all uniform.

    Anyways, I guess I should be thanking SBT rather than flaming since their screw up led to me getting a great deal on this awesome Polaris. Thanks SBT!!!

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    Last edited by K447; 10-30-2013 at 08:52 PM.

  5. #5
    Polaris John's Avatar
    Join Date
    Jul 2012
    St.Petersburg Forida
    Wow that thing burned up I would have thought water cooling related. I had one virage that sucked up a plastic bag was able to get it out with some dawn dish soap.

  6. #6
    Rasta Mon Condoms We Be Jammin!!!!! TxPro1200's Avatar
    Join Date
    Aug 2006
    the more i thought about this one the more i thought about the head o-ring.if the cooling passages were block all the heat would have been around the exhaust port not the intake side where the intake charge would help cool it.was there even a fragment of an o-ring in there??so here's the thousand dollar question?what good does a warranty do when they just blow up and after two they say tough luck.

  7. #7
    Banned User
    Join Date
    Jun 2010
    Milwaukee WI
    If it was getting water in the cylinder I bet the crank is compromised as well. I would tear it down completely and check it all out. It would suck to replace that cylinder only to have a crank fail shortly after that.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Quote Originally Posted by HU112BU View Post
    ... It started using the leaking area as an exhaust port and eventually torched through the head and out into the water jacket resulting in the head cover and the outer cylinder taking the full heat from the combustion. It ruined the head as well as the cylinder...
    The part I am impressed with is that the water pressure in the jacket didn't drown the cylinder and kill combustion shortly after beginning to breach the water jacket wall.

    During the power stroke the combustion gases would of course over power the water pressure, but on the intake portion of the cycle? Perhaps the water jacket was so full of exhaust gasses that there just wasn't much actual water around

  9. #9
    @ TxPro1200- Not even a fragment of an o-ring, however, I'm impressed that the outer o-ring hung in there and kept itself sealed while the cover and cylinder were red hot. Not sure where in the warrantee it states "one replacement per customer", but I was informed by both the PO and SBT that they wouldn't replace this one. Bad for them, good for me I guess.

    @ BryanP- After thinking about it I have to agree with you that a complete disassembly is in order to ensure that everything is up to spec. I also want to check out the other cylinders to see if they are "chunked out" around the top where the cylinder meets the sleeve. I'm still scratching my head as to how this happened. More often than not when you heat a cylinder to 400 degrees for about 30min in the oven , the sleeve will slide right out without much prompting unless it was damaged and out of shape. More on the crank prognosis once it's out of the machine and on the bench.

    @K447- Very good question. Not sure of this myself unless as you mentioned the hot exhaust gasses, or the metal being super heated kept the (pardon the pun) water at bay. Additionally, with a sizable hole in the dome area, how in the world did it maintain enough compression to sustain combustion? Has this ever happened to anyone else? Kinda hard to miss installing an o-ring upon assembly but I guess it can happen....

    Just a note that while trying to explain this to my gf, I used the Challenger shuttle disaster as a reference with great success. Here's a pics of what expansive super heated gasses can do when your O-rings aren't sealed as this image of the recovered solid rocket booster from the Challenger shows....

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  10. #10
    I have built many polaris engines and I can tell ya that if the o-ring was missing from the begining then that cylinder would have filled up with water very fast and hydrolocked, the cylinder would have broke right off the case. You said the first engine cooked the same cylinder the first time around and who knows why the guy even replaced the original engine, maybe the same cylinder on the original engine failed too. You said the original gray shit fuel line was still there and we all know what that leeds too, I think your cooling was working fine thats why the indicater never turned color on the head so that leeds back to lean condition from fuel starvation, if that cylinder was getting that hot to melt the aluminum then you can bet it got hot enough to melt the o-ring too. You can see it ran lean it started dishing out the center of the piston, look back at the pictures.

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