cam shaft check

Discussion in 'Airheads' started by blaine.hale, Sep 28, 2013.

  1. blaine.hale

    blaine.hale Long timer

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    1974 r90 cam saft. There's a little knick where one of the followers goes. There's approximately 100k mile on this cam. Still think it's usable? I'm looking to throw it in my r90 with 64k miles as the tip on my cam sheered and the drill/tap of a bolt isn't as centered as I'd like it to be.

    [​IMG]
    #1
  2. Plaka

    Plaka Brevis illi vita est

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    Looks like erosion on the top of the lobe. It's toast.

    Wanna buy a cam?:D
    #2
  3. motu

    motu Loose Pre Unit

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    By the wear marks the follower isn't running on that part of the cam. If it was my bike, that nick wouldn't be there, and the cam would be in my engine.
    #3
  4. disston

    disston ShadeTreeExpert

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    Judging from that photo I'd agree with Motu and run that cam. A couple more photos would be nice tho if you could get a little different angle. Or better focus (I have the same problem making these Macro photos. Do we have a thread here somewhere about taking photos?)
    #4
  5. chasbmw

    chasbmw Long timer

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    There has be a reason why that cam was removed from its engine and I think that you are looking at it. Have you seen the follower that ran on that lobe?

    Your choices are:
    Put back to your old cam, you could leave it as it is and go to an electronic ignition, Boyer on the cam or an alternator mounted ignition.

    You could fit the 320 degree small seal cam available new from Motoren Israel

    Buy another secondhand small seal 308 degree camshaft
    #5
  6. JonnyCash

    JonnyCash turd polisher

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    That's what the camshaft of my 75/5 project bike looks like. I deliberated on using it, or even TIG welding some silicon bronze into the crater, but Pokie is sending me a good one. On my bike the lifters were beat, each one of them.
    #6
  7. JonnyCash

    JonnyCash turd polisher

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    Looking at it some more, it really does look like the lifter doesn't even bear on it there. What about filing or grinding the chip smooth with a dremel, and stay out of the contact area? That would help prevent further chipping, and make it easier on the lifter if it does contact.

    Or just come up with another camshaft.
    #7
  8. blaine.hale

    blaine.hale Long timer

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    The cam was removed by me ;) I'm already on a boyer, my option is a crank mounted expensive ignition and still have an unbalanced cam, possibly causing issues...or replace the cam and be worry free.
    I might try to find a 336 cam or better stock replacement at this point. Anyone have any price gauges on a 336 and a location to buy? I've checked out MI...woo, spensive! I also like the idea of a 324 cam.
    #8
  9. blaine.hale

    blaine.hale Long timer

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  10. disston

    disston ShadeTreeExpert

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    Hey Blaine,

    Only thought of this today. It may work. We have talked about it but nobody I know of has tried it yet.

    [​IMG]

    The tip of the camshaft is called the quill and it is removable. You need a press to do this. You have one original camshaft with damaged tip, broken threads, of the quill. And a replacement camshaft with damaged lifter lobe?

    My only reservation is about the fit of the quill in the bore of the camshaft. This would have to be checked. It may need matching or they may already match. I don't know.

    As far as changing from one size seal to the other I think there's a difference in the cover?
    #10
  11. Stan_R80/7

    Stan_R80/7 Beastly Gnarly

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    With the r90 camshaft out of the engine, it can be placed in a lathe and the hole bored true and then tapped for a M7x0.75 or M8x1 thread. The final solution may require a custom threaded stud with a M7x0.75 threads on the cam end and M6x1 threads for the advance.

    Honing around the nick area helps but it looks like there is another issue on the lobe with that cam: but that may be from the photography. Good luck!
    #11
  12. chasbmw

    chasbmw Long timer

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    My June 75 is a Small seal cam......I don't think that the Boyer will be much Bovvered by the securing bolt being slightly off centre. I would run the original cam and check the Boyer timing with a strobe. I think that you will find it works OK
    #12
  13. blaine.hale

    blaine.hale Long timer

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    It does work just fine. Timing has been checked many times. Really I'm being paranoid but I think things that aren't perfectly centered and balances will cause issues in the long run. Plus, if I could get a 336 for under $200, I'd be extremely pleased. I'd love to extract the quill and press it into my existing can but I have no idea how to begin with that. Buying a full replacement might be much easier. 336 hunting time! I'm in no rush BTW. I've got the r75 where I want it :)
    I'm pulling the heads and pistons on the r90 tomorrow and soda blasting the stupid amounts of carbon Then balancing the con rods.
    Fred, I'll be asking to borrow your fancy scale soon :)
    #13
  14. bmwrench

    bmwrench Long timer

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    I'm posting this in hope of keeping any one from being injured. I have removed the quill from a cam by heating the front journal of the camshaft. I expected to have to ease the quill out with a plier. Instead, the quill shot out of the cam and into a 25 foot ceiling. I shudder to think what might have happened were I not so lucky.
    #14
  15. JonnyCash

    JonnyCash turd polisher

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    :eek1 I've got a few junk camshafts, and now I know what I'll do with them. This is gonna be fun!
    #15
  16. blaine.hale

    blaine.hale Long timer

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    This sounds like a lot of fun in a contained area!
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  17. Plaka

    Plaka Brevis illi vita est

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    if you just have an off center hole in the cam and are using a crank mounted ignition, you have no worries. The imbalance is extremely close to the center of rotation, not inches away. Remember the cam on a points bike is unbalanced anyway, it has to push the points open with a one lobed cam!. The bearings are sized to take the vibration. you can also just put a bolt in the hole and saw it off. no more imbalance, it's all solid metal. you can also drill a small hole in the top plate of the advance assembly to balance it. or just pull the quill and go with a crank mounted.
    #17
  18. blaine.hale

    blaine.hale Long timer

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    You're making too much sense Plaka, stop it.

    If I don't manage to find a 336 for a deal, I think I can find comfort in what you're saying and move on.
    #18
  19. supershaft

    supershaft because I can

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    Hopefully you know that our points cams have two lobes directly opposite of each other and balancing each other out? Not that that matters but . . . .Comfort? I get no comfort in knowing that even a broken clock is right twice a day. I want a working clock around to know when! :)
    #19
  20. Plaka

    Plaka Brevis illi vita est

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    MAX has a small seal 336* (for 75/5) for $262, $10 cheaper then the stock 308*. Methinks I need to up the price on the 308 I'm selling. Stock for a 60/5 is a 284*.

    I think you'd get more grins out of a lightened flywheel than a cam and you don't have to screw with getting it to work with the carbs.. Combine that with a low rear end and you'll be fragging alternator rotors. I've done a 900cc top end w/ stock75/5 rear end and it was big grins. (and needed reinforced rotors). You could get the front end in the air without smoking the clutch (too much:D).Add some slide carbs....


    BTW, I know exactly how you feel. I am very prone to perfectionism. But "perfect" is for the Gods. If I try to be "perfect" I will insult them. unwise. I'll also never get the project done. So 'good enough' and go ride it. Owning things will no more make me happy than owning perfect things. Better to go out and play.
    #20