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Engine Help (Valves)

JigrahJigrah Registered User regular
edited August 2008 in Help / Advice Forum
Alright this is part two of my asking for engine help.

Long story short.

I was driving on the interstate, suddenly I have a large loss in power, RPM's do not reach above 6,000 and there is no change in noise. I can go around 50 mph and do so for about 12 miles until I find a motorcycle shop.

The shop looks at it and tells me I have low compression, probably because of a piston ring.

I take apart my bike and realize that my rings/pistons/cylinderblock are all just fine. However I find out that when I put a solvent in my exhaust it leaks through one of the valves. I did the same for all the intake valves and the intake that is across from the leaking exhaust, is also leaking.

What would cause the valves to be leaking so suddenly? Do I need to replace to valves or can I just reseat them? If I just reseat them what do you think the problem is that caused them to fail in the first place?

Jigrah on

Posts

  • Lord YodLord Yod Registered User regular
    edited August 2008
    What kind of bike is it?

    Lord Yod on
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  • PirateJonPirateJon Registered User regular
    edited August 2008
    Did you check the valve clearance specs or just eyeball them? You don't say, but then again you did to a full tear down...

    PirateJon on
    all perfectionists are mediocre in their own eyes
  • JigrahJigrah Registered User regular
    edited August 2008
    PirateJon wrote: »
    Did you check the valve clearance specs or just eyeball them? You don't say, but then again you did to a full tear down...

    I am not all that knowledgeable about engines so I could have easily messed up. As I understand Valve clearances are adjusted by the cam shaft. The cam shaft is off so shouldn't all the valves be at their greatest height?

    I might have the wrong understanding of what the valve clearance is though too.

    It's a 1996 Suzuki Katana, 600.

    Jigrah on
  • PirateJonPirateJon Registered User regular
    edited August 2008
    Engine internals are a bit out of my depth and my bike has hydralic valve adjustment anyway.

    But as I understand it you check clearences under/near the camshaft lobes when the piston is at TDC. You're looking to see that the valve is seated fully and there's enough 'play' in the system. I would think removing the camshaft would prevent you from checking the clearance.

    Do you have a service manual to check?

    Also this link (way down at step 32) may help.
    http://www.billsbikesnservice.com/cam.htm

    PirateJon on
    all perfectionists are mediocre in their own eyes
  • JigrahJigrah Registered User regular
    edited August 2008
    PirateJon wrote: »
    Engine internals are a bit out of my depth and my bike has hydralic valve adjustment anyway.

    But as I understand it you check clearences under/near the camshaft lobes when the piston is at TDC. You're looking to see that the valve is seated fully and there's enough 'play' in the system. I would think removing the camshaft would prevent you from checking the clearance.

    Do you have a service manual to check?

    Also this link (way down at step 32) may help.
    http://www.billsbikesnservice.com/cam.htm

    When the camshafts are off the springs should be pulling the valve's fully into the seat. Which I guess would be TDC if you had the camshaft on there. The valves are not fully seated even though that camshaft isn't on.

    I am thinking that the clearances might have been off which led to this problem, any insights if this is plausible?

    Jigrah on
  • fuelishfuelish Registered User regular
    edited August 2008
    To little clearance can burn an exhaust valve. To little clearance on an intake can cause power loss but a valve failure would be unusual. The valve would run hot because most of the heat transfer away from the valve occurs while the valve is closed and it contacts the seat. This will quickly burn an exhaust valve because it gets most of the heat from combustion. But I suppose it could happen with an intake valve. More likely the exhaust valve had to little clearance, or that one cylinder was running lean and the intake valve saw enough heat to gall the guide and keep the valve from seating.
    You need to pull the valves and have a look at them and the seats. If they are stuck it will be real obvious because they should just slip out of the guides(If they stick when you reach the groove the keepers fit in, you need to file off any burrs, on the stem so you don't damage the guides, but this is not related to your problem) If they bind at all the guides need to be reamed or replaced. If the valves look OK(Even with out much experience you can probably spot the damaged area, or take it to a shop) You can proabably lap them in. If they look damaged, the seats need to be recut and the valves replaced.
    I gotta go eat dinner, but if anything is unclear, I will be back in a little while.

    fuelish on
    Another day in the bike shop Pretty much what it sounds like. The secret lifestyle, laid open.
  • Donovan PuppyfuckerDonovan Puppyfucker A dagger in the dark is worth a thousand swords in the morningRegistered User regular
    edited August 2008
    Jigrah wrote: »
    When the camshafts are off the springs should be pulling the valve's fully into the seat. Which I guess would be TDC if you had the camshaft on there. The valves are not fully seated even though that camshaft isn't on.

    Uh-oh. You need to check that the valves aren't stretched. The seats may be recessing into the head, the valve heads may be badly worn, the valve springs could be dead. Was the engine getting hot? Do you rev the life out of it regularly? It's unusual for a whole set of springs to go at once, especially only on one cylinder. Same with the valves stretching. Are there clearance shims missing from the loose valves?

    Donovan Puppyfucker on
  • JigrahJigrah Registered User regular
    edited August 2008
    fuelish wrote: »
    To little clearance can burn an exhaust valve. To little clearance on an intake can cause power loss but a valve failure would be unusual. The valve would run hot because most of the heat transfer away from the valve occurs while the valve is closed and it contacts the seat. This will quickly burn an exhaust valve because it gets most of the heat from combustion. But I suppose it could happen with an intake valve. More likely the exhaust valve had to little clearance, or that one cylinder was running lean and the intake valve saw enough heat to gall the guide and keep the valve from seating.
    You need to pull the valves and have a look at them and the seats. If they are stuck it will be real obvious because they should just slip out of the guides(If they stick when you reach the groove the keepers fit in, you need to file off any burrs, on the stem so you don't damage the guides, but this is not related to your problem) If they bind at all the guides need to be reamed or replaced. If the valves look OK(Even with out much experience you can probably spot the damaged area, or take it to a shop) You can proabably lap them in. If they look damaged, the seats need to be recut and the valves replaced.
    I gotta go eat dinner, but if anything is unclear, I will be back in a little while.

    Most of the pictures I have seen of damaged valve heads (from getting too hot) are quite noticeable, chunks missing and that kind of thing. So I was afraid that wasn't the problem. Usually those are all exhaust valves though and not intake. Could there be a link between the exhaust and intake valve? They both seep solvent (although the exhaust much quicker) and are in line with each other.


    Thanks.

    Jigrah on
  • Donovan PuppyfuckerDonovan Puppyfucker A dagger in the dark is worth a thousand swords in the morningRegistered User regular
    edited August 2008
    For the valves to be so loose that there is no seat pressure, in my opinion either the valves are stretched, the valve springs are kaput, or the seats are totally hammered to hell.

    Valve springs usually don't die unless you have gotten them so hot they've lost their temper (pretty hard to do, unless you set fire to the bike) or you rev it so hard and for so long you manage to hammer the springs soft.

    So I think the the engine has been getting hot, and either the seats have receeded into the head, or the valves have stretched. Either way, it's a head job.

    Because if one cylinder is that bad, it usually means all the cylinders have been suffering the same, and will soon fail as well.

    It could be that that one cylinder has been running lean and over heating, and that would lead me to suspect something wrong with your carburettor on that cylinder.

    If that cylinder has been running hot, you'll want to check the bearings, liner, piston and rings, the gudgeon pin and the conrod too. Running hot will fuck all of those components up.

    Donovan Puppyfucker on
  • JigrahJigrah Registered User regular
    edited August 2008
    For the valves to be so loose that there is no seat pressure, in my opinion either the valves are stretched, the valve springs are kaput, or the seats are totally hammered to hell.

    Valve springs usually don't die unless you have gotten them so hot they've lost their temper (pretty hard to do, unless you set fire to the bike) or you rev it so hard and for so long you manage to hammer the springs soft.

    So I think the the engine has been getting hot, and either the seats have receeded into the head, or the valves have stretched. Either way, it's a head job.

    Because if one cylinder is that bad, it usually means all the cylinders have been suffering the same, and will soon fail as well.

    It could be that that one cylinder has been running lean and over heating, and that would lead me to suspect something wrong with your carburettor on that cylinder.

    If that cylinder has been running hot, you'll want to check the bearings, liner, piston and rings, the gudgeon pin and the conrod too. Running hot will fuck all of those components up.

    Do you know of any tests or how to determine if it is the carb that is misjetted or something?

    I moved down from CO to TN, so there is a huge difference in altitude. I wonder if that might have anything to do with it running lean.

    Jigrah on
  • PirateJonPirateJon Registered User regular
    edited August 2008
    its getting the same fuel but way more o2 now, so it's probably lean.

    I can't help you with the rest, but will be watching with interest.

    PirateJon on
    all perfectionists are mediocre in their own eyes
  • fuelishfuelish Registered User regular
    edited August 2008
    Jigrah wrote: »
    fuelish wrote: »
    To little clearance can burn an exhaust valve. To little clearance on an intake can cause power loss but a valve failure would be unusual. The valve would run hot because most of the heat transfer away from the valve occurs while the valve is closed and it contacts the seat. This will quickly burn an exhaust valve because it gets most of the heat from combustion. But I suppose it could happen with an intake valve. More likely the exhaust valve had to little clearance, or that one cylinder was running lean and the intake valve saw enough heat to gall the guide and keep the valve from seating.
    You need to pull the valves and have a look at them and the seats. If they are stuck it will be real obvious because they should just slip out of the guides(If they stick when you reach the groove the keepers fit in, you need to file off any burrs, on the stem so you don't damage the guides, but this is not related to your problem) If they bind at all the guides need to be reamed or replaced. If the valves look OK(Even with out much experience you can probably spot the damaged area, or take it to a shop) You can proabably lap them in. If they look damaged, the seats need to be recut and the valves replaced.
    I gotta go eat dinner, but if anything is unclear, I will be back in a little while.

    Most of the pictures I have seen of damaged valve heads (from getting too hot) are quite noticeable, chunks missing and that kind of thing. So I was afraid that wasn't the problem. Usually those are all exhaust valves though and not intake. Could there be a link between the exhaust and intake valve? They both seep solvent (although the exhaust much quicker) and are in line with each other.


    Thanks.

    Part of that is because they love to show photos of maximum destruction, that occured under the absolute worst conditions. Usually the motor starts having problems way before total destruction. So the damage may not be so obvious. Look at the valve face. There should be a sharp "line" all the way around the face. This is where the valve seats against the seat in the head. If there is a problem the line will blur or widen. This might show on the seat in the head.
    There probably is a link between the two.
    If the motor was tuned for CO it will be running lean in TN. SInce it has carbs the tune between cylinders can be pretty different. You could remove the top plate from the carbs, remove the CV diaphragm and take out the slide. Now remove the main needle and see what position the clip is in, or how many spacers are under it if it only has one clip position.Now compare it to the other carbs. Check the idle mix screw as well(You may not to be able to adjust this, they are often under a sealed plug). Gently screw it in til it bottoms, counting in quarter turns, and compare to the other carbs.
    You also want to look for a loose or damaged boot betweent he carb and head, because that can also cause a severe lean condition.

    fuelish on
    Another day in the bike shop Pretty much what it sounds like. The secret lifestyle, laid open.
  • JigrahJigrah Registered User regular
    edited August 2008
    fuelish wrote: »
    Jigrah wrote: »
    fuelish wrote: »
    To little clearance can burn an exhaust valve. To little clearance on an intake can cause power loss but a valve failure would be unusual. The valve would run hot because most of the heat transfer away from the valve occurs while the valve is closed and it contacts the seat. This will quickly burn an exhaust valve because it gets most of the heat from combustion. But I suppose it could happen with an intake valve. More likely the exhaust valve had to little clearance, or that one cylinder was running lean and the intake valve saw enough heat to gall the guide and keep the valve from seating.
    You need to pull the valves and have a look at them and the seats. If they are stuck it will be real obvious because they should just slip out of the guides(If they stick when you reach the groove the keepers fit in, you need to file off any burrs, on the stem so you don't damage the guides, but this is not related to your problem) If they bind at all the guides need to be reamed or replaced. If the valves look OK(Even with out much experience you can probably spot the damaged area, or take it to a shop) You can proabably lap them in. If they look damaged, the seats need to be recut and the valves replaced.
    I gotta go eat dinner, but if anything is unclear, I will be back in a little while.

    Most of the pictures I have seen of damaged valve heads (from getting too hot) are quite noticeable, chunks missing and that kind of thing. So I was afraid that wasn't the problem. Usually those are all exhaust valves though and not intake. Could there be a link between the exhaust and intake valve? They both seep solvent (although the exhaust much quicker) and are in line with each other.


    Thanks.

    Part of that is because they love to show photos of maximum destruction, that occured under the absolute worst conditions. Usually the motor starts having problems way before total destruction. So the damage may not be so obvious. Look at the valve face. There should be a sharp "line" all the way around the face. This is where the valve seats against the seat in the head. If there is a problem the line will blur or widen. This might show on the seat in the head.
    There probably is a link between the two.
    If the motor was tuned for CO it will be running lean in TN. SInce it has carbs the tune between cylinders can be pretty different. You could remove the top plate from the carbs, remove the CV diaphragm and take out the slide. Now remove the main needle and see what position the clip is in, or how many spacers are under it if it only has one clip position.Now compare it to the other carbs. Check the idle mix screw as well(You may not to be able to adjust this, they are often under a sealed plug). Gently screw it in til it bottoms, counting in quarter turns, and compare to the other carbs.
    You also want to look for a loose or damaged boot betweent he carb and head, because that can also cause a severe lean condition.

    Fuelish where do you live, I am going to buy you a drink.

    Thanks.

    Jigrah on
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