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Thread: valve stem cracked

  1. #1

    valve stem cracked

    I'm doing the top end again on my Chief after about 15k miles (it was time!) and I found that the front cylinder exhaust valve stem had a crack in it, and I don't know why.

    here's the crack:


    and the valve guide was worn into an oval:


    I expected to see wear on the pushrod, but nothing obvious:


    Doesn't seem like normal wear, the rear exhaust and both intakes are fine. The pushrod doesn't have any unusual sideways play in it, so one thought I had is that the valve seat is not lined up correctly with the valve guide?

    Curious if anyone has seen this before, the bike ran very well but compression had dropped off and it was getting finicky to start. Thanks for your ideas!
    Last edited by Pisten-Bully; 04-19-2019 at 08:13 AM.
    1946 Chief - take apart and put back together
    101 Scout - building stage

  2. #2

    Re: valve stem cracked

    I would be surprised if that is a crack. Likely just a line of the end of travel. You MUST use quality HARDENED guides from Kiwi or Greer or you are just wasting time and money! Gunk that thing off before you pull the top unless you are going all the way.

  3. #3

    Re: valve stem cracked

    Quote Originally Posted by indianut View Post
    Gunk that thing off before you pull the top unless you are going all the way.
    Busted! At least I covered up the holes into the case!

    Gonna look at the that stem again after work, the line doesn't go all the way around and I can catch it with my fingernail so I just thought it was crack. New valves and guides coming from Greer's. thanks Danny!
    1946 Chief - take apart and put back together
    101 Scout - building stage

  4. #4

    Re: valve stem cracked

    As indianut said the mark on the valve stem looks like a wear line. I wonder if the valve guide wear could be a weak or broken valve spring.

  5. Re: valve stem cracked

    Howdy sir,

    Vendor shall remain nameless but before installing any guides measure from the bottom off the base flange to the top of the newly acquired guide and compare to your existing ones. For added insurance I would blue or otherwise mark the length of the valve stem and insert it back into your old guide still in the cylinder to determine what “head room” you have in the closed position to where the stem flutes to the valve head. Only after installing my new guides did I discover the new exhaust valves could not seat because the guides were too long and fouled the stem flutes. Not a fan of needlessly hammering guides in and out I had to make a piloted tool to turn off the required length to enable the valves to close, aargh! And no, I did not have recessed valve seats.

    Though I run no seals on the 348, installed a set on the 346 and recommend them. Indians run some very loose guide clearances of .004 thou which enables carbon on the exhaust side to travel down the guide where it mixes with oil and becomes a very effective grinding paste. That’s that sludge you encounter when raising your covers to adjust your valves. That residue has been greatly diminished with seals.

  6. #6

    Re: valve stem cracked

    Quote Originally Posted by peterg440 View Post
    Howdy sir,

    Only after installing my new guides did I discover the new exhaust valves could not seat because the guides were too long and fouled the stem flutes. Not a fan of needlessly hammering guides in and out I had to make a piloted tool to turn off the required length to enable the valves to close, aargh! And no, I did not have recessed valve seats.
    Any time I have encountered that it has been the problem of the valve which is fixed in a minute on the lathe.

  7. Re: valve stem cracked

    Howdy sir,

    Are we assuming removing material off the back of the valve head? I wasn’t/wouldn’t be keen to remove the nearly 180 thou required off this or really any moving part to achieve the objective when an adjoining fixed position one offers the same opportunity without strength or function compromise.

  8. #8

    Re: valve stem cracked

    Quote Originally Posted by roho46 View Post
    As indianut said the mark on the valve stem looks like a wear line. I wonder if the valve guide wear could be a weak or broken valve spring.
    Thanks roho, I'm sure Indianut and you are right, it's a wear line. Tried to part the "crack" by back bending the stem and couldn't open up any space at all. Closer inspection shows no wear line on one side, so the side that ground away at the valve guide shows the wear.

    Dunno about valve seals, however, I always guessed oil was drawn up from the cam case, up the push rods and onto the valve stem and into the valve guides thanks to a bit of vacuum from the valves not being sealed at the top.
    1946 Chief - take apart and put back together
    101 Scout - building stage

  9. #9

    Re: valve stem cracked

    Quote Originally Posted by peterg440 View Post
    Howdy sir,

    Are we assuming removing material off the back of the valve head? I wasn’t/wouldn’t be keen to remove the nearly 180 thou required off this or really any moving part to achieve the objective when an adjoining fixed position one offers the same opportunity without strength or function compromise.
    The longer the guide the better, especially on an Indian and the cases I have seen it would appear the problem was with a crappy repo valve not a crappy repo guide! I would think a guide would have more force exerted on it than the head of a valve anyways.
    Last edited by indianut; 04-19-2019 at 08:00 PM.

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