intake valve guide
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Thread: intake valve guide

  1. #1
    Junior Member 400nitro's Avatar
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    intake valve guide

    I had a burned intake valve replaced at 12000 miles. the mechanic said the top of the guide wont hold a seal on, so he put it together without the seal. I think the stem was mushroomed and forced through. he said they remove the seals on racing engines for lubrication? anyone ever have this happen. im thinking of having it done correctly and at the mileage maybe replacing the piston, I think it was run hard because how slow they are on the road. any advise is appreciated thank you.

  2. #2
    Senior Member Fred's Avatar
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    You are likely wise to replace the possibly mushroomed valve, perhaps a new guide as well and certainly a new guide seal. Inspection of the cylinder might reveal advisability of new rings, a hone and possibly a new piston. They may still have life in them. If you are doing the disassembly yourself the labor saved could well pay for a Wiseco piston and a complete head service & re-build.
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    Super Moderator JerseyJeeper's Avatar
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    Replace your mechanic if he put it together without offering you the option of replacing the guides.. No seals "may" make sense on a drag bike but generally it never makes sense.

    If you decide to replace the guide yourself. Heat the head in an oven, they come out fairly easy and you can cook a snack while your doing it.. Don't forget the clip...

    Always grind off the top of a mushroomed valve stem or at least file it down before attempting to pull it out through the guide.

    Or... buy a good used head off of ebay or someone here.

    Chances are the valves were run way to loose due to lack of maintenance and the rocker smashed them into little mushroom tops.
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  5. #4
    GOF
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    Yeah, I'm sorry. But that guy sounds less than professional. Do the job right. Either replace the head or get the head rebuilt properly.
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  6. #5
    Junior Member 400nitro's Avatar
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    thanks for the help. I think ill also do the base gasket update. its very lean, takes long to run without the enricher out. Is there any known carb specs that work. its a 08 at 400-2200 elevation. thanks again.

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    Senior Member elime's Avatar
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    For the fun of it look into the exhaust port. I have seen some heads with a lot of casting flash (???) limiting the size of the exhaust port. Some heads are pretty good. Some aren't. You can compare it to the size of the exhaust pipe where it bolts onto the head. I bet the pipe is a lot bigger.

    I opened up the port on one of my heads and it seemed to help the performance. If you are going to have the head all apart anyway and if you have a die grinder it might be something you want to do.

    I started opening up the port before I took the picture. Originally it was a smaller hole.
    You can see the gasket on the pipe and the same gasket in the head. A lot of metal can be removed.
    PA280049 (2).JPG
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    Senior Member elime's Avatar
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    This what it looked like when I quit grinding and there was plenty of metal left to remove if I had chose to.

    A straight in view.
    Head on view.jpg

    Looking along the floor into the combustion chamber.
    floorA.jpg
    admiral, Fred, jtstdub and 1 others like this.
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  9. #8
    Member Denn's Avatar
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    If you run an intake valve without the seal you will burn a little oil but probably nothing worse will happen. If you run an exhaust valve without the seal, you will probably coke up the valve stem and get sluggish performance especially prior to warming completely up.

  10. #9
    Senior Member elime's Avatar
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    Quote Originally Posted by Denn View Post
    If you run an intake valve without the seal you will burn a little oil but probably nothing worse will happen. If you run an exhaust valve without the seal, you will probably coke up the valve stem and get sluggish performance especially prior to warming completely up.
    On one of my TW's with a bad exhaust stem seal the back side of the valve was covered with hard carbon about an eighth to a quarter inch thick. A lot of hard carbon had been deposited in the exhaust port / passage too. Is that what you meant by saying "coked upped"?
    Last edited by elime; 04-13-2019 at 12:03 AM.
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  11. #10
    Junior Member 400nitro's Avatar
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    thanks for all the input. if it doesn't carbon up on an intake valve I think I will run it this season the way it is. it has over 12000 miles ill do the complete top end over winter, I don't want to tear it apart now anymore. I'm old and slow I really like this bike and the low gearing.

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