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white exhaust valve

Discussion in 'Chat & Tech Info' started by baloches, Aug 22, 2010.

  1. baloches

    baloches Cruisin' Guzzisti

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    I had the LH exhaust manifold off to seal my phase sensor and to check my oil pressure switch, and noticed how white my exhaust valve was.
    With these engines running so lean, I'm wondering what to make of this, or is it normal/acceptable...

    [​IMG]
     
  2. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    Better to be as it is than to be caked with carbon.
     
  3. GTM®

    GTM® Administrator Staff Member GT di Razza Pura

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    If you see my post under the original PC-V thread; https://www.guzzitech.com/forum/160/2686.html -- I have charts for the AFR's hovering in the critically lean areas for much of the general running. So much so that it's hard to believe they will issue a warranty... which is also why the immense amount of heat from the engine. I have a fix.
     
  4. Mike.C

    Mike.C GT Reference

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    I'm with John on this one. If the lean running was a major issue I would have thought that we would have heard of reports of engines with exhaust valve problems and failures, but AFAIK that is not the case.

    Sure the engines run lean in stock form but I suspect that the designers might know a thing or two about the balancing act that they have run between emissions requirements and the ability of the engine design to withstand it's internal operating conditions.

    That's not to say that Baloches' valve colour is acceptable or normal. I do know that my Breva exhaust valve when the bike was stock looked similar and I did wonder the same thing as you, but it was not nearly as white... maybe your fuel is a bit different than ours.
     
  5. pete roper

    pete roper GT Godfather!

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    When the exhaust gasses are leaving the combustion chamber they can be very hot. The only way the valve can dump heat is through the stem/guide interface and through the seat when the valve is closed. Exhaust valves do run hot, if you usually run your bike fairly hard? That's what they will end to look like. The colouring is uniform and there are no signs of impending disaster. Not sure which model it is but I have not heard of ANY big blocks that have been prone to dropping or burning valve heads or having the seats fall out of the heads, (Not since early Ambos anyway! :mrgreen: ). In the absence of any other issues I say 'Put the pipe back on and stop worrying ye great big-girl's blouse!' :D

    Pete
     
  6. guzzi jon

    guzzi jon High Miler GT Contributor

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    These are the same designers that have not been able to attach a fuel line in the tank for 7 years :D
     
  7. Mike.C

    Mike.C GT Reference

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    Yes well I take your point, but we are talking about an internal engine component that has AFAIK no reported history of failure, so it seems to me that the design is sound.
     
  8. baloches

    baloches Cruisin' Guzzisti

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    Thanks for the information. I wasn't worried (just spooked!), the engine has been running the same since new, I'm pushing 60k km's now. I've never had the chance to take note of different engines exhaust valves conditions and wanted to run this by you guys.
    They are able to make the engines put up with the heat created by emissions control, but I would feel much better if it wasn't running so hot. Traffic in and out of Montreal is horrendous and on hot days I really feel for all these metal bits...

    I always keep a very light load with an easy throttle hand on the engine when traffic gets moving again until it is cooled down. Aside from these conditions all is good, pinging will happen only at extremes and is easily avoided but enrichening the lean parts must really make the bike even more enjoyable.
     
  9. guzzibob

    guzzibob GT Reference

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    Clearly you are being careful about this, all to the good. And quite possibly the engineers have the valves/valve guides made to deal with this. As others have said, lack of top end failures suggests this is true-though by old time Guzzi standards the amount of mileage on most all of the newer bikes is still pretty modest. Still, as you suggest, cooler/less lean is better for many reasons, & may take a long time to show up. As others have reported & I have personally experienced, going to Todd's reflashed ECU brings subjectively obvious less heat coming off the motor-& per his report 40F degrees lower head temps as measured. Not to mention less if any pinging & obviously improved performance.
     

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