R90/6 camshaft sprocket...

Discussion in 'Airheads' started by porkNbeans, Dec 29, 2014.

  1. porkNbeans

    porkNbeans n00b

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    Hello people:
    The R90 is in the living room for the winter, ostensibly for a crank sprocket & timing chain replacement ( noisy timing chest when oil is hot), and damn if that cam sprocket doesn't look worn as well. All literature that I've seen implies that the camshaft be removed from the engine before pulling/pressing the sprocket, but are there any adventurous/foolhardy souls out there who have managed to replace the cam sprocket w/o removing from rhe engine? What would be the ill effects of happily hammering the new sprocket on with the cam still in situ? Trashed seal?
    Ruined oil pump? Many thanks for any input,
    Eli
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  2. Bill Harris

    Bill Harris Confirmed Curmudgeon

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  3. robtg

    robtg Long timer

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    The cam really needs to be removed to properly set the end clearance.
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  4. porkNbeans

    porkNbeans n00b

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    Ah, thanks for the responses, guys! I have just such a puller (from Ed Korn, back in the day), but is setting the end clearance the only reason one would undergo the considerable hassle of cam removal? Is there truly no way to slip a ~.005 feeler gauge behind that sprocket while pressing (tapping) it on like one would with the crank sprocket ?? I'm a lazy, lazy man, and I JUST pulled the trans mid-spring for a spline lube....
    gaaah!!!
    #4
  5. supershaft

    supershaft because I can

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    +1

    Don't over heat the tips of the teeth while you are heating the sprocket. If the color of the metal changes so has the temper! It's easy to do!

    The later simplex cam sprockets almost never wear. The earlier and much heavier duplex cam sprockets wear on a regular basis. Crank sprockets? The duplex crank sprockets wear worse and faster but the simplex sprockets wear on a very regular basis too.
    #5
  6. Stan_R80/7

    Stan_R80/7 Beastly Gnarly

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  7. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    I replace the cam sprocket with the cam in place, unless the cam needs to be removed for other reasons. You can easily set the cam bearing endplay with the cam in the engine-- I use a longish strip of 0.10mm (0.004") brass shim stock, cut in a "fork" to fit the shaft, for the feeler gauge. Easier to maneuver. Make sure the cam is levered forward to zero-out the residual endplay at the rear of the bearing. When you heat the cam sprocket, it _will_ slip on without drag--if you have the feeler gauge in place, the axial play will be set in one fell swoop. If the sprocket doesn't slip easily, pull it again, and heat it a little more-- tapping it will cause problems.

    Forgot to mention: loosen the valve adjusters to remove pressure from the lobes.

    I'll let someone else explain their steps in removing a cam from an assembled, mounted engine... :eek1

    --Bill
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  8. NSA

    NSA Silently Listening

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    The key to this puller is the "die" sitting next to it. Before I had a clue how the whole cam setup worked, I looked at mine and though "I can just put a three jaw puller on there and pop the gear right off". Trust me... that's not good for the threaded snout on the end of the cam.

    LOTS of heat in the center of the gear, for both removal and replacement. When cold, that gear will not go on smoothly, and makes setting end play a nightmare.

    Full disclosure: I ended up taking my cam out the "correct" way, since I had the engine out anyway. I learned my first lesson that nothing on an airhead is "obvious" as it appears.

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  9. porkNbeans

    porkNbeans n00b

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    Man, I love this (virtual) place!
    Thanks!
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  10. supershaft

    supershaft because I can

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    I think the oil in the engine and stuff will throw off your end play reading too much. Plus, it's going to be a miracle to get it right in one or two times. Beginners luck will be a must.

    I remove the cam with the engine in the frame. I do everything with the engine in the frame but rear main bearings. The frame is the best engine holder. Huge time saver too.
    #10
  11. Pokie

    Pokie Just plain Pokie.

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    If you're going to try to replace the cam sprocket while the cam is in place, make sure you DON'T press on the end of the cam or quill, damage will result. Use something like an old wrist pin to slip over the quill and press on that.

    Personally, it's not all that hard to pull the tranny, flywheel and oil pump, back off the rockers and pull the cam. After all, it's winter and you're not in a hurry. Plus it gives you the opportunity to inspect the condition of those other parts.

    I have found that when you cut corners (being in a hurry) it ends up taking more time when things don't go well.
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  12. Disston

    Disston ShadeTreeExpert

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    +1
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  13. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    -1.

    You sometimes need to remove as few parts as necessary. If the transmission (swingarm bearings, driveshaft bolts and boot, clutch cable, airfilter clamshell, one or both carbs, and speedo cable) or clutch, or flywheel (need a main seal?) or oil pump cover (need o-ring?) or oil pan (the tappets might try to slide downhill and need to be repositioned to get the cam back in) with gasket.

    If you are worried about the endplay being off, double-check it with a dial indicator. If you are worried that the feeler gauge is not precise enough, don't use the feeler gauge and set the endplay at zero when you slide the hot sprocket on, and use the removal puller to pull it out to a dial-indicated endplay.

    Or at least this is how I've done it for 35 years. I ride year-round and don't want the bike tied up on the lift all Winter... :D

    --Bill
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  14. supershaft

    supershaft because I can

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    How many times have you changed a timing chain in airheads in the last 35 years?

    I think the trouble with your advise is that between the heat and jumping around on the shaft with a puller and the oil involved, too much pure luck is going to be involved getting the adjustment within .0015"
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  15. Pokie

    Pokie Just plain Pokie.

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    12 degrees below zero and snow here, I don't think I'm going for a ride.
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  16. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    45 degrees and sunny, rain forecast for the weekend and I went riding today. Wuss'd out, had a eee-lectric jacket liner.

    But Ft Collins/CO does have much nicer scenery than the Wolf Creek Wildlife Management Area and Slick Lizard (tho you'd be hard-pressed to beat the BBQ)

    Have a great New Year's !!!!

    --Bill :)
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  17. Disston

    Disston ShadeTreeExpert

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    37* and Sunny. No wind. Did 1/2 the PRT seals on my R90/6.
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  18. boyblu

    boyblu Adventurer

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    And just wait till you get to that master link--putting the teensy keepers on from behind--
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  19. porkNbeans

    porkNbeans n00b

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    I actually had good luck with that last time around: with the master link at roughly 5 o'clock, I globbed red BMW spline lube in the inside of the link and the circlips, pushed them into place with a small pair of hemostats, and gingerly drove them home with a small screwdriver. Badda bing!
    #19