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Thread: Burned out exhaust valves

  1. #1
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    Burned out exhaust valves

    Hi All. I have a 2002 1150RT with about 28,000 on it. Coming home from the rally two up and pulling a trailer we had gone about 10 miles one morning and were on a long steep uphill grade when the bike lost power without warning. We managed to make it to the rest area at the top of the hill where we pulled over. A quick check showed the bike was running on only the Left cylinder. Changing plugs around made no difference and there was a spark on the R. Anyway we limped back to the closest dealer. After having the bike for a few hours he advised me the exhaust valves were burnt to the point there was no compression on the Right. His diagnosis was that the valves on both heads would require extensive work. The mechanic attributed this to the bike running hot and ethanol in the gas. Is this a common problem on these bikes? is it normal that this would show up as a sudden loss of power with no advance warning?

    Would appreciate your thoughts.

    John

  2. #2
    BUDDINGGEEZER
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    Quote Originally Posted by 20975 View Post
    The mechanic attributed this to the bike running hot and ethanol in the gas. Is this a common problem on these bikes? is it normal that this would show up as a sudden loss of power with no advance warning?

    Would appreciate your thoughts.

    John
    I do not like ethanol fuel. With that out of the way, your mechanic has made a statement not based on fact. Ethanol fuels don't burn valves. As a matter of fact, ethanol burns cooler than gasoline.

    Intake valves usually don't burn, at least not as often as exhaust valves. Intake valves are cooled by incoming air/fuel and valve contact with the valve seat. exhaust valves are cooled by valve seat contact.

    Anything that interferes with valve cooling or creates extra heat in the valve or head can lead to premature valve failure. Running a lean air/fuel mixture (often due to vacuum leaks), retarded ignition timing, detonation (from too much compression or low octane fuel) or preignition (from hot spots caused by deposits in the combustion chamber or too hot a spark plug)will cause higher combustion temperatures and can burn valves.

    Incorrect valve lash (tight valves) interfere with correct valve seat contact. As the seats wear away and the valves recede into the head, valve lash is lost. Eventually there is little or no lash left and the valve makes poor contact with the seat, overheats and burns.

    I suspect the cause of your burned valve is a combination of summer heat, the load placed on the engine pulling the hill 2 up with trailer and too tight exhaust valves.

    In the western (higher elevations) part of the country I have noticed the AKI index of fuel is a couple points lower than the rest of the country. Evidently 85 AKI high elevation fuel equals 87 AKI elsewhere. Is it possible you bought high elevation fuel, dropped out of the mountains into lower elevation, which could make the fuel not have enough octane and cause preignition with the heavy engine load?

    If the other valves aren't burned, especially the intake valves I can't see why they would need extensive work, but I'm not looking at the engine.

    Ralph Sims

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    Burning valves out is a gradual thing, not something that happens at once.

    A simple compression check or a leak down test would confirm pressure loss from the combustion chamber. We're talking about 10-15 minutes to run the test.

    If anything happened inside the compression chamber, a large amount of carbon may have gotten forced under the valve holding it open.

    JON

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    Thanks Ralph, interesting comments. Only the exhaust valves need work. You are also correct we had dropped out of higher elevation to lower. We fueled in Enterprise Ore and then dropped down to Clarkston Washington. We were on the long grade out of Clarkston when the problem occurred.

    John

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    Registered User MOTOR31's Avatar
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    A key question would be how long ago were the valves adjusted and were they done to factory specs?

    I agree that the most likely cause of burned exhaust valves would be improper valve clearance. That is likely due to 3 possible reasons. Either the valve body stretched, the clearance was not set properly quite a few miles before or the valve seats have started receding into the head not allowing the valves to close all the way.

    Another possible reason would be improper ignition timing.

    My money would be on improper clearance as the most likely cause.
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    Pepperfool GSAddict's Avatar
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    Quote Originally Posted by DarkCloud View Post
    Burning valves out is a gradual thing, not something that happens at once.

    A simple compression check or a leak down test would confirm pressure loss from the combustion chamber. We're talking about 10-15 minutes to run the test.

    If anything happened inside the compression chamber, a large amount of carbon may have gotten forced under the valve holding it open.

    JON

    Mine burned on a high speed pass from one moment to the next just like the guy above - outside temp was 45F - the leanest point in the operating temperature span. The was nothing gradual about it.
    The head specialist I took it to said the alcohol in the fuel (higher combustion temps) likely loosened a piece of carbon - He said all it takes is for the valve to be propped open for a couple of cycles and the damage is done. These engines run so lean to begin with.
    FYI My valves all had the correct clearance prior to teardown.
    '
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    It's all about the details.

  7. #7
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    Quote Originally Posted by Motor31 View Post
    A key question would be how long ago were the valves adjusted and were they done to factory specs?

    I agree that the most likely cause of burned exhaust valves would be improper valve clearance. That is likely due to 3 possible reasons. Either the valve body stretched, the clearance was not set properly quite a few miles before or the valve seats have started receding into the head not allowing the valves to close all the way.

    Another possible reason would be improper ignition timing.

    My money would be on improper clearance as the most likely cause.
    Carbon is usually the culprit - see my post above
    '
    Ufda happens..........

    It's all about the details.

  8. #8
    Rally Rat
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    I used to work on a few police bikes, which get run harder than civilian bikes. Several of them burned valves (as well as a few civilian bikes). Our examination led us to believe that enough carbon due to oil consumption led to the valves being unable to seat. We shortened the guides slightly on the port end, which is a traditional fix of sorts, to reduce this possibility. We also modified some of the bikes pistons to accept a different second ring to reduce oil consumption.

  9. #9
    mrhall
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    This is why you should run Chevron Techron in your fuel a few times a year and buy Chevron gas. Polyether Amine (PEA) prevents harmful build-up.
    Very good product and along with a little octane booster for trips.

  10. #10
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    Burnt valves can be from poor initial valve seat shaping at the factory. Not unheard of by any means. If the bike has this, both sides should be reworked the same way.
    Anton Largiader 72724
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    I might also ask what RPM were you running the bike. Lugging can be a little harder on the valve. The oil cooler pump is hooked to the crankshaft so lower RPM is less oil, and less cooling to the head. Also, the exhaust valve is open longer, and it can get a bit hotter too. Pulling a load like you were, I would suspect that about 4000 would be a good minimum rpm, and highway in 5th better than 6th, or even 4th if you are running at 60 or less. running easy at 5000 RPM is much less stress than running hard at 3500 RPM. With a trailer I do not think I would ever use 6th, it is really too high for USA speeds.

    Rod

  12. #12
    E_Page
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    Quote Originally Posted by MRHALL View Post
    This is why you should run Chevron Techron in your fuel a few times a year and buy Chevron gas. Polyether Amine (PEA) prevents harmful build-up.
    Very good product and along with a little octane booster for trips.
    I'm sure that helps, but it's not a sure preventative. I run almost exclusively Chevron Premium and just lost a cylinder due to burnt valves. Service writer told me his best guess as to cause was that some carbon buildup broke loose. Mine is also a 2002 R1150 RT, but with 66,500 on it.

    In the thread I had going about this problem (Running Rough, Near Stall), Bikerfish morpbably identified the problem for me... that I commonly drive at lower RPMs. I guess I need more speed.

  13. #13
    mrhall
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    I do think riding w/speed helps. I always ride hard/fast and I can't see any carbon building up in my motors.
    I probably keep it burned out.
    The Techron bi-annual treatment really works good tho!
    Texaco now has it, being Chevron owned.

    E.page, where you at in n.ca?

  14. #14
    Bluenoser
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    I was wondering what octane or type of gas you where running at the time? What rpm you where running up the hill?

    Burnt exhaust valves happen very quickly and yes carbon holding a valve open is a usual culprit. Also any amount of pre igntion would raise the cylinder head temp to the point where it would burn valves. Seeing as it really only affected one side I would suspect thevalves may have been set a little too tight.

    Being an air/oil cooled engine keeping the revs up when under a load ( like the bike in question ) is about the only way you can hopefully prevent it from getting too hot. That being said long uphill climbs with an overloaded bike will raise the engine temp to the extremes and any weak point will show itself. Rather than trying to keep up the speed you might have been better off to select a lower gear & slow down to lessen the load on the bike
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    Registered User MOTOR31's Avatar
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    Are both exhaust valves burned in that cylinder? If so. it would be a coincidence that both valves got a piece of carbon blocking the seal so they both fail at the same time.
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