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Thread: Something broke in my head

  1. #1
    Registered User krpntr's Avatar
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    Unhappy Something broke in my head

    I just took the bike for a short ride. When I started it was hard starting (unusual) then it blew a lot of smoke (not unusual for being on the side stand) But when I left the shop I had to visit it was harder to start and then would only run on one side. I barely made it home on one cylinder. I took the valve cover off and pulled the spark plug. The exhaust rocker was about a quarter inch from the push rod. When I looked down the spark plug hole I could see something round where there should be nothing. Did I just drop a valve seat? Do I need a new bike? It is a '82 R100 with 180k.

  2. #2
    Registered User skiteach's Avatar
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    That would be first guess. NO you don't need new bike! Fix it!
    '73 R75/5
    Never had a bad day skiing!

  3. #3
    Administrator 20774's Avatar
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    The '82s was in the middle of the run with the bad seat metallurgy. I'd be very surprised if the head was original after 180K miles. That said, it would appear that you'll need to take things apart. This would be fortuitous if that's all that happened and that the valve didn't break off and bust a hole in the piston. Ouch, that would be disastrous.
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    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    With a 180,000. Probably needs a complete topend. Combustion chamber could have gotten pretty dinged up also. I'm guessing you may also need a new piston, rings, and cylinder. Also time to get rid of the pollution air pump garbabe attached to the air cleaner housing and the head. Dissasembly will give you most of the answers.

  5. #5
    Registered User krpntr's Avatar
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    Its apart and

    I think the damage is minimal. The head is dinged as well as the top of the piston, the seat did pop out but it did not break and leave little bits every where. Yes,total top end is in the very near future. Rings, valves, and guides. I think a good machinist can fix the dings.
    Now my main delema is I just spent all my extra cash on a low miles Honda CM91 for around town and it needs a carborator. Perhaps now is the time to sell my bits and pieces and the field find K100 that is taking up space in my shed with no tittle. And then find a good machine shop in the neighborhood. I guess I'm lucky it happened close to home as I was just about to go check out the conditions at the top of the North Cascade Hwy pass. I wasn't planning any long trips in the near future any way; but I'll be back though. See you in the flea market.
    Matt.

  6. #6
    Registered User krpntr's Avatar
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    Here is a photo

    Is there a way to anticipate this so in the future I won't have seats a pop'n?
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  7. #7
    Registered User krpntr's Avatar
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    And the piston

    Oh the horror.
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  8. #8
    Grammarian no, Rider yes ISAMEMON's Avatar
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    I think you lucked out
    pull the cylinder and see what shape its in. no gouges, Id ring it. get the head fixed and watch the flea market for the parts you need to rebuild it right in the future. with 180k your looking at a upper end and a few seals and gaskets anyway

  9. #9
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    If an airhead has 100,000 miles, it would be a good idea to start thinking about having a top end done. Top in life on airheads vary. Usually when the valves don't seem to be holding their clearance for very long, smoking a little too much, etc. Time to pull the heads off and have the work down. Better to just beat the problem to the punch. Bike will run much better and your fuel economy should increase and that alone should make it worth being done. Like I stated earlier, if the air pump emissions is still in place , way past time to remove and jettison. That system just burns up the exhaust valve and causes the faster deterioration of the head.

  10. #10
    Registered User krpntr's Avatar
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    emission pluming

    Yea that stuff got jettisoned long ago. However, I had been having problems with leaky header crossover joints and loud popping. I replaced the headers and mufflers a few years ago and then went on a road trip last year to central Florida. When I got home I adjusted the valves and replaced my front tire. Since then I was wintered in till recently. But the 100k limit is probably the best idea. This is not the first time this happened to this head. Last time was about a that long ago. Probably should make repairs at 80k. Come to think of it, just before the break I heard some popping as I rolled off the throttle. It was a deep sound, different that the previous popping. Oh well, lesson learnt. Thanks, sometimes I tend to push machinery to its outer limits and expect too much. I am, sad to say, guilty of motorcycle abuse. And I swear by the tenants of the air-head cannons I will repair this bike and do my best to continue to flog it down the highway.
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  11. #11
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    Your not the only one who floggs their bike, I've been guilty of it too. That's a nice lookin bike ya got.

  12. #12
    Grammarian no, Rider yes ISAMEMON's Avatar
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    so the heads have popped seats before ? I thought fixing the seatsx was a perm fix, if not
    find later model heads that dont have the metellergy issue

    interesting rear turn signals

  13. #13
    Registered User krpntr's Avatar
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    Turn signals

    Yes thanks to the brilliant engineering from the fatherland the clamps have vibrated a slot in the tube at the inside of the notch, They won't stay horizontal, but they won't fall off either. Just another sign of her advancing age. And yes,I also thought the valve seat should be a permanent fix . I have been checking my valve adj every 3 or 4k miles and they were always spot on. The only time there was any change was when I checked when I got home from Fl. It has always been an insta-start kind of bike. Other than hard starting that last morning, and popping on the roll off, it was fine.

  14. #14
    doktortim
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    Quote Originally Posted by Krpntr View Post
    Yes thanks to the brilliant engineering from the fatherland the clamps have vibrated a slot in the tube at the inside of the notch, They won't stay horizontal, but they won't fall off either. Just another sign of her advancing age. And yes,I also thought the valve seat should be a permanent fix . I have been checking my valve adj every 3 or 4k miles and they were always spot on. The only time there was any change was when I checked when I got home from Fl. It has always been an insta-start kind of bike. Other than hard starting that last morning, and popping on the roll off, it was fine.
    A NASA machinist will destroy BMW heads. A NASCAR machinist will destroy BMW heads. Only a BMW machinist can fix them right every time. The seats are held by a precise tolerance fit. Too tight and when knocking it home you peal a sliver of metal out of the seat bore. Not tight enough and it falls out in short order.

    You have to heat the head to 250f or more and freeze the seats with perfect measure to get them in with no damage and when they normalize they are plenty tight. The very same procedure is used on VW and Porsche air cooled heads. A similar process is used to replace the guides.

    Who's a BMW machinist? Beemershop is where mine will go when needed. I don't think there are more than a dozen proven competant BMW machists in the US. Same for tranny rebuilders. Same for spline machinists.

    Those who do the work right NEVER overcharge.

  15. #15
    Registered User krpntr's Avatar
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    BMW certified machine shop

    I agree,I will not take it to any the local performance shops. There is a shop in Seattle I know of that does (or did) the air head work for the local dealership. The last machinist that worked on this head is no longer available. That was almost 20 years ago. Probably beyond the warranty expiration date. And that brings up my greatest fears about these things. The specialty shops that know these rare old machines are disappearing as their trade moves onto the modern age. I'm hoping I don't have to do this again to this machine. Right now my only other riding option is a '69 Honda CM91 I recently fount on Craigslist. And even though it is a groovy little motor bike, it a'int no big motorcycle.

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