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  1. #1

    WTB: Two 1200 Carbureted Heads

    Needing two cylinder heads for the TX1200. The engine was an SBT rebuild and assembled without a head gasket O-ring on the mag cylinder. Bought a replacement head, only to find that SBT machines the head domes to lower compression. I saw this on an SBT Yamaha 1100 head but thought it was a Yamaha thing. Now I find out that any engine from SBT has the domes opened up. (!) So, I'd rather find two heads to match my one stock one than one SBT low compression one. I would also gladly swap the two I have for two (2000-up) regular ones if anyone has a need for these. The "good" head is on the left, while the SBT ones are on the right...Click image for larger version. 

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ID:	319585 I take back all the good things I've said about SBT. Two of the cylinders were ruined not by the bores being rusted, but because the sleeves were pressed in while the cylinder housing was too cold, resulting in fractured pieces wedged in the ports. Unbelievable....


  2. #2

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    do you have sbt 1mm over pistons in it if so you'll have to get the domes from them or have a set opened up for there pistons

  3. #3
    Yeah, it actually did have the 1mm OS pistons in it. However, since that engine is pretty much destroyed, I am converting an injected one over to drop back in. I rebuilt it awhile back and it's been sitting in the garage. It's .5mm over so I'm needing the heads to go on that. Is that why these heads were relieved was to accommodate the 1mm OS pistons?

  4. #4

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    it's part of the reason they open them up because 1mm is 85mm and the squish would be to tight

  5. #5
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    They open up the squish band area on the heads, but they also machine out the heads to increase volume and reduce compression. Thats what the inner ring that has been machined out is. I have a set of heads that look exactly like that.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by HU112BU View Post
    ... Two of the cylinders were ruined not by the bores being rusted, but because the sleeves were pressed in while the cylinder housing was too cold, resulting in fractured pieces wedged in the ports. Unbelievable....
    Photos please.

  7. #7
    Tjdriver's Avatar
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    I have a dome from a 99 genesis. It's in excellent condition.

  8. #8
    Sorry for the delay K447, I didn't get any emails updating responses to the thread. Here are a few snaps of the damaged cylinders. The one with the chunks out of the top cylinder surround showed no sign of any debris anywhere. Whether the pieces were flushed out through the cooling system or were missing prior to assembly is unknown. The other one (center cylinder) shows pitting to the head and is missing one big chunk from the intake port. The opposite intake port chunk was lodged in the intake (holding it to show the size of the piece in the pic) and the port next to it shows a fracture and clearance around the sleeve. It wouldn't have been long before this one let some shrapnel loose into the cylinder as well. I also took a picture of the bottom of the sleeves so you can see that the only undamaged cylinder was a stock Polaris sleeved cylinder, whereas the other two that had chunks out of the thin sleeve surround were SBT re-sleeved units.
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  9. #9
    Here's the snap of one of the SBT units next to the Polaris one. You can see the differences in the skirts, showing that the two failing ones were definitely re-sleeved.
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  10. #10
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    If you are going to a motor that is .5mm over, I would just buy 3 new heads from a Polaris dealer. They are only about 30 bucks a piece new. Part number 3021122

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