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Thread: Doing your sprag? Caution!

  1. #1
    A303
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    Doing your sprag? Caution!

    Replaced my sprag clutch in November using a BMW one. The sprag is fine but, on the advice of an 'expert', I fitted the sprag retaining circlip, even though the BM sprag has no lateral retaining slots (if you see it, you'll know what I mean). In the words of the 'expert', "It's not going anywhere is it?"
    Well it was going somewhere - round my bloody engine and gearbox in large chunks and tiny specs of ally swarf, as Griff (who is a REAL expert) found out when he changed my oil yesterday. Luckily it looks like it mostly got trapped by the oil filter and the bike has been on track and done a couple of thousand miles since then so hopefully (touchwood) no harm done.
    If you're using the BM sprag, leave the circlip out - it serves no purpose other than getting chewed up into pretty sparkling granules which you can use for your kid's art project!

  2. #2
    BB1000
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    whats the advantage of using a BMW sprag.....cost......or just better

  3. #3
    Baby Twin
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    Cost i believe, about half the price

  4. #4
    A303
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    About a third of the price for basically the same item (just works the other way round so turn it or rebuild it - do a search for info on that). The BMW single that it's meant for is also made by Rotax.

  5. #5
    Baby Twin Les Tap's Avatar
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    Apart from the startmotor just spinning,are there any other signs that the sprag is on its way out ?,cheers

  6. #6
    A303
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    Quote Originally Posted by Les Tap View Post
    Apart from the startmotor just spinning,are there any other signs that the sprag is on its way out ?,cheers
    'Orrible graunching noise, gets progressively worse until it won't start at all. Don't ask me how I know.
    Follow the correct starting proceedure to avoid it.

  7. #7
    camngetit
    Guest
    what are the prop starting procedures

  8. #8
    redratbike
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    starting procedure is ...do not touch the throttle, adjust the cold start lever on the left hand clip on ,press starter...should burst into life almost instantly...keep your hands on the cold start lever just in case you have pulled it back too far as you dont want to hit 8000rpm from cold...with practice you know where to set it too...i leave mine running at 2000-2500 till its warmed up..I.E. the "cold" alert stops flashing on the dash and i let it warm up to at least 50 degrees before sliding the cold start lever back....mine sits outside so might need a longer warm up to a bike sat indoors

  9. #9
    crasher76
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    I agree, even in this warm weather use the cold start lever, the 'prilla needs all the help it can get firing into life. I have tried starting with none, and progressed to half but she didn't fire. I use full cold start which sets it into life at 3000rpm, i knock it down to 1.5-2k as soon as possible. I imagine they are all slightly different though. find out what works best for yours and stick to that!

  10. #10
    Baby Twin
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    where is this cold start lever?

  11. #11
    AMA Pit Boss Sprocker's Avatar
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    Quote Originally Posted by kibb_dj View Post
    where is this cold start lever?
    Left handlebar switch unit (for the old models tho' , i think the newer shapes have automatic choke )

  12. #12
    One Liter Duc Eater Sabre's Avatar
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    This lever also acts as a great cruise control as I found on the M5 yesterday. Keeps the bike at a steady 80 in top while you rest/flex your throttle hand.

    Dont do this in traffic, children!

  13. #13
    Si600
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    The new (nicer ) shape does indeed have an automatic choke. I believe it turns off at 70C if that's relevant to anyone

    The problem with leaving the choke open is that the richer air/fuel mixture can "wash" the oil off the piston bores causing accelerated wear.

  14. #14
    Evil Twin RSV-TWIN's Avatar
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    my 'fast idle' was quite erractic... but now works perfectly after a TB & TPS balance !!

    next up for me is getting a bigger battery... 14amp i believe !?

  15. #15
    A303
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    Quote Originally Posted by Si600 View Post
    The problem with leaving the choke open is that the richer air/fuel mixture can "wash" the oil off the piston bores causing accelerated wear.
    If it was a choke, that might be a problem!

  16. #16
    Baby Twin Les Tap's Avatar
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    Yep,coz as we all know,the only thing the fast idle lever does is open the butterfly's a tad,and I mean a tad providing its been set up proper !!!! with a 1.6mm gap between the anvils just above the tickover adjuster when fully open unlike mine which had about a 3mm gap !!!!! and probably led to the death of my sprag

  17. #17
    Si600
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    Quote Originally Posted by Les Tap View Post
    Yep,coz as we all know...
    Clearly not all of us know these things

  18. #18
    AMA Pit Boss
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    I can actually see my fast idle adjuster move the throttle twist grip, the other thing I found the other day was that the butterflies had come loose and were rattling around in the spindle........................now fixed with new screws and loctite.

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