airhead front crank bearing

Discussion in 'Airheads' started by JonnyCash, Dec 10, 2012.

  1. JonnyCash

    JonnyCash turd polisher

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    On a junk crank I have laying around, I went to pull off the front bearing to then remove the timing gear. I has not been my impression that this bearing is usually much trouble to remove. This crank has been out of service for 8 years, but isn't rusty. I put my three legged puller on the bearing and started putting the pressure to it, but got nothing. I then got out the propane torch and gave the bearing more and more heat, but still got nowhere. Since this is a junk crank, and will never again be used as a crankshaft, I went for the OA torch, surely that will get it. More and more heat, tightening my puller harder than seemed prudent. The balls and inner race were glowing brightly but still not budging. The puller's hub broke, and the bearing is still in place.

    This was all very interesting, and an eye-opener. I have been planning to replace the timing chain and crank gear on my /5 this winter, but after this, I'm worried that this sort of thing will happen, and I'm not willing to destroy good parts, like I have this junk crank. I guess if it came to this on my /5 I'd be removing the crank from the engine and cutting the bearing off, but I sure don't want to have to do this.

    Is this bearing often this kind of trouble to remove? I just can't believe how hard it is stuck on there. For the record, generally speaking, I am a patient worker who does not break things. I've done a fair bit of this sort of thing, but this seems to be a special case. Thanks for any insight.
    #1
  2. bmwrench

    bmwrench Long timer

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    I pull the front bearing and crank sprocket simultaneously by pulling against the back side of the sprocket. They are sometimes quite difficult, and you need a good puller.
    #2
  3. disston

    disston ShadeTreeExpert

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    A bigger puller will probably get it off. If you were pulling the bearing and not the gear/bearing combo I can't see it not coming off tho. Are you pulling the two parts or just the bearing? What sort of backing part did you break? I use a bearing splitter for this.

    Sounds like you are using a steering wheel type puller. Too small anyway, what ever it is.
    #3
  4. DiabloADV

    DiabloADV Semi-Occasional

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    A proper splitter and a press will get anything off. I broke a puller trying to get a timing sprocket off (and tore up a tooth on the sprocket). Took it to the shop where they have a press. Bink. Came right off with no fuss. Pushing is better than pulling...

    But yes, that means taking the crank out of the motor.
    #4
  5. Cordless

    Cordless Two Wheel Addict

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    I took that bearing off a junk /5 crank with my 20 ton HF press. I set it in the press then squirted Kroil into it for a day. Worked very well.

    Upon closer look, I think that crank could be reused.

    The press was fairly cheap when I used a 20% off coupon and a sale price. The press does take up some room in the shop, though.
    #5
  6. hardwaregrrl

    hardwaregrrl ignore list

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    Did you hit the puller with an impact wrench?
    #6
  7. photomd

    photomd Been here awhile

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    #7
  8. brocktoon

    brocktoon Been here awhile

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    I tried a decent-sized bearing puller. The Clymer manual recommends putting a penny on the nose of the crankshaft to prevent the bearing puller from damaging the threads. I ended up pushing the penny right into the nose. :puke1 Bye-bye crankshaft (it was damaged anyway).

    I ended up biting the bullet and bought the Airhead multi tool set from Cycleworks. Not cheap, but everything came apart and went back together smoooooooooothly.
    #8
  9. supershaft

    supershaft because I can

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    I guess you mean that the crank is in the case and the front bearing web is stuck in the case? Not the bearing stuck on the crank? If that's the case, heat the case more.
    #9
  10. JonnyCash

    JonnyCash turd polisher

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    On my /5, the crank is still in the bike. The crank I fought with yesterday was out of a junk engine. I got the crank out of the case by unbolting the front main bearing carrier from the case. That all came out very easily, it's the bal bearing that goes into the timing cover that I cant get off of the crank.

    Someone asked if I used an impoact driver on the puller bolt. No I didn't, but I did give it a few smart whacks with a hammer while it had a good strain on it.

    I'm glad to have this as a preview of what I might encounter when I deal with the timing chain on my /5.
    #10
  11. disston

    disston ShadeTreeExpert

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    Johnny,

    There are many different types and sizes of bearing splitters. This is a small one;

    [​IMG]

    Here is a puller and bearing splitter. Looks big and strong enough but with nothing for size comparison it's kinda hard to say.

    [​IMG]

    You will pay hundreds if not thousands of dollars for these tools if you get quality stuff. The "Tool Trucks" like Snap On or Matco are the most expensive. Mail order you can find good quality from OTC and for just a little less than the Tool Truck tools.

    Some of the stuff at Harbor Freight is OK but I don't like most of it. I do own some Chinese. Can't argue with the price.

    After you take into account the cost and number of tools you would have to acquire it is probably more prudent to get the tool made by Cycle works;

    [​IMG]

    I don't own this because I have all the other odds and ends enough to do the job. This looks like #1 quality and reports are that it will do a good job.
    #11
  12. Stan_R80/7

    Stan_R80/7 Beastly Gnarly

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    #12
  13. Humboldt Airhead

    Humboldt Airhead Adventurer

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    It sounds like your 3 jaw puller was on the outside race of the bearing. With this set up you will fight the bearing comming off as it will dish slightly forcing the inner race into the crank.
    If you are able to get behind the inner race it would probably come off. That is why it is better to grab behind the sprocket with a splitter.
    #13
  14. JonnyCash

    JonnyCash turd polisher

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    It was indeed under the outer race.That makes perfect sense, and I hadn't considered that. Thank you. I've got another larger gear puller, whose legs I can alter a bit to let me get under the gear. Its nice to have this junk crank to experiment with. Tomorrow, I'll work on it and check back in. Thanks all for your suggestions.
    #14
  15. bmwrench

    bmwrench Long timer

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    I never heard of using a penny in the end of the crank until recently. I screw a short 8mm socket head bolt into it. This protects the end of the crank and helps keep the puller screw centered.
    #15
  16. supershaft

    supershaft because I can

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    Oh I see. I have never had one of those bearings not come right off with a puller. I have the same suggestion: more heat.
    #16
  17. JonnyCash

    JonnyCash turd polisher

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    I don't think you really read my first post. I used way more heat than you'd want to use on a crank that's going to ever see service again. Hell, it even started to melt the stamped metal ball retainer, and totally blued the snout of the crank. This crank is going to be used in an artistic effort, not a bike so I don't care, but when I go to pull the gear and bearing on my /5 to do the timing chain, that much heat won't be an option.
    #17
  18. supershaft

    supershaft because I can

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    Oh, now I see a little better. I would cut and chisel it off. If that doesn't do it you are going to have to gring it off anyway.
    #18
  19. driggles

    driggles Adventurer

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    So when pulling a duplex timing sprocket from the crank, what kind of puller is the best to use? Clymers shows a two jaw puller but I've found that the jaws on mine will bear more on the timing chain than on the sprocket itself. On the '78 the chain is masterless so it can't come off first.....any suggestions from the experts? Can I pull that sprocket with the jaws set against the chain? Or should I try to grind the jawas to fit better? Thoughts?
    #19
  20. chasbmw

    chasbmw Long timer

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    I have just used a dremel to cut my chain off.

    I would prefer not to go through the hassle of taking off and replacing the socket as a complete set with camshaft chain and all.

    I will use a split link duplex chain as a replacement they are cheap enough
    #20