1997 Beta Techno 250 question?

Discussion in 'Trials' started by Happy Seal, Sep 4, 2013.

  1. Happy Seal

    Happy Seal Long timer

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    I had a bit of overheating on my Techno. The bikes starts and runs perfect for about 15 minutes then I start to hear gurgling. I had tested the fan and switch but still overheating. There is a little trickle coming out back of head that is barely noticeable. So I pulled the head off and see a clean spot where I presume coolant has cleared off the carbon.

    [​IMG]

    Question is, There are two o-rings for the head/cylinder seal. I didn't see any cuts or deformities on the o-rings or the mating surfaces. The cylinder walls look great and the piston looks fine.

    The o-rings are soft and pliable. Has anyone seen this happen before? I was expecting more of a problem and am reluctant to think this is just as easy as two o-rings.

    what do you guys think?

    Thanks.
    #1
  2. lineaway

    lineaway Long timer

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    I would say just the O-rings, but I would be checking the water pump also.
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  3. Happy Seal

    Happy Seal Long timer

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    I just put in a new water pump and engine ice a few months ago. The o rings just give out heh? I work on industrial air compressors and they use viton o-rings as well so it doesn't surprise me that they fail but I like to see some sort of defect on the seal or ring to prove that it was the problem.
    #3
  4. lineaway

    lineaway Long timer

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    Sounds to me as you have a problem some where. When the fans start to go bad they will be intermittent as far as starting every time. You can tell by if you can push start it with your finger when you think it is starting to get hot.
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  5. Twin-shocker

    Twin-shocker Long timer

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    I would guess the problem is probably directly related to head bolts not being torqued down properly. Did you check them for tightness before removing head?
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  6. ericm

    ericm Been here awhile

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    Check that the head's bottom surface is still flat. you can use a piece of glass and feeler gauges.
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  7. Boom Boom

    Boom Boom Been here awhile

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    Go back to the water pump.
    Very easy to knock a tooth off the plastic gear that drives it.
    Was chasing a heating issue on an 06, it was missing 2 teeth and that was the problem.
    Hold a little tension on the pump impeller and slowly turn the engine over to see if you hit a spot where the pump impeller does not turn with the engine.
    If burning coolant you will smell it.....
    #7
  8. motobene

    motobene Motoing for 44 years

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    Gurgling is a good sign of over heating - or a radiator cap that cannot maintain any pressure - thus the boiling temp is lowered. Is your fan coming on during the gurgling?

    Uneven carbon buildup on the head is normal. It's a reflection of flow dynamics during combustion. On my GG bikes, buildup tends to be greater toward the exhaust and sometimes a little off center. The less-carboned spot I don't think is due to coolant. It's possible of course, especially if you are seeing the level drop and you have no drips on the ground. If you are getting a significant amount of coolant into the combustion chamber, it tends to create white smoke.

    Got that head oriented right? As in cylinder and head passages lined up? I know that sounds silly, but I had to ask.
    #8