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    #1

    Rotor spun on crank

    Went to the gas station today...got the dreaded "starter whirring but engine not turning" routine. Thought maybe I had sheared the starter clutch bolts but instead found out the rotor had started turning on the end of the tapered crank.

    This was despite meticulous effort on my part when I reassembled it earlier--I had cleaned the rotor and the shaft with degreaser, made sure there were no burrs, and torqued the rotor bolt to the specified 72 ft-lbs.

    Guess I'll torque it even tighter. I hate to use my air impact wrench on this bolt--don't like anything beating on the crank, but maybe the hammer-blows may help drive it home a little better. Sure wish I had access to dry ice....I guess I could heat the rotor up in the oven at 200 degrees but somehow I doubt the missus would go for that. Any other suggestions?
    Tags: None
    #2
    Loctite. Red.


    Then hope you never have to remove it again.
    Bertrand Russell: 'Men are born ignorant, not stupid. They are made stupid by education.'

    ​

    Comment

      #3
      taper shaft

      Iknow I will get flack for this one, but I never dry assemble a taper fit, or the bolt, I litely oil the bolt treads and contact shoulder and I oil the taper shaft and wipe off any excess, reason being that the bolt retains the rotor by stretch and not by bolt bind, and an interferance fit needs the very lite oil to keep it from binding while trying to seat its self on the taper shaft, if you galled the shaft from the slippage then I would get some med- to fine valve lapping compound and lap ir back in first, this is how I have done them on many bikes and never had one come back to my old shop

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        #4
        How bad are the tapered surfaces scuffed on the crank & in the rotor

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          #5
          They're not scuffed, I wasn't far from home.

          I do have an old electric griddle (your basic hot plate) and I think I'll use it to heat up the rotor, say to around 225 degrees or so. Sure wish I had some dry ice to pack the crank end.

          Big debate I'm having (with myself): whether to use the air impact to tighten the rotor bolt, or just use the regular torque wrench cranked up to around 100 ft-lbs--Clymers called for 72...

          Comment

            #6
            Re: Rotor spun on crank

            Originally posted by BillC
            Went to the gas station today...got the dreaded "starter whirring but engine not turning" routine. Thought maybe I had sheared the starter clutch bolts but instead found out the rotor had started turning on the end of the tapered crank.

            This was despite meticulous effort on my part when I reassembled it earlier--I had cleaned the rotor and the shaft with degreaser, made sure there were no burrs, and torqued the rotor bolt to the specified 72 ft-lbs.

            Guess I'll torque it even tighter. I hate to use my air impact wrench on this bolt--don't like anything beating on the crank, but maybe the hammer-blows may help drive it home a little better. Sure wish I had access to dry ice....I guess I could heat the rotor up in the oven at 200 degrees but somehow I doubt the missus would go for that. Any other suggestions?
            Bill,

            This used to happen regularly on my '83 1100E. Finally the shaft got worn enough so there wasn't enough taper for the rotor to tighten. I Took it to a dealer who 'poured' purple Loctite on the shaft and tightened it down. A week or so later some of the Loctite broke loose and locked up my starter clutch causing the starter to be spun by the engine. Needless to say I ended up with a melted starter. I took the rotor back off, cleaned everything up, measured the shaft with a micrometer, wrapped a piece of feeler gauge stock of appropriate thickness around the shaft, re-assembled and tightened the rotor back up. I haven't touched it again in over ten years.

            Joe
            IBA# 24077
            '15 BMW R1200GS Adventure
            '07 Triumph Tiger 1050 ABS
            '08 Yamaha WR250R
            "Krusty's inner circle is a completely unorganized group of grumpy individuals uninterested in niceties like factual information. Our main purpose, in an unorganized fashion, is to do little more than engage in anecdotal stories and idle chit-chat while providing little or no actual useful information. And, of course, ride a lot and have tons of fun.....in a Krusty manner."

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              #7
              Fortuantely neither the crank or the rotor wasn't galled up.

              I wasn't too thrilled by the Loctite approach. So I heated up the rotor on the electric skillet to about 225 or 250 and just now put it back on. I tightened the bejeezus out of the rotor bolt. After it cools I'll put the cover back on, maybe tonight I can ride.

              Comment

                #8
                Hey Billc where are you in relationship to Nashville?

                Comment

                  #9
                  gallatin

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                    #10
                    I worked at the domino's in gallatin as an assistant for acouple of months. Maybe we can ride some once I get my bike legal and road worthy. The roads between springfield and gallatin would be a pretty fun ride.

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                      #11
                      Drop me a message when your bike's on the road again... Mine's back together and it started OK, hopefully this time the rotor will stay in place

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                        #12
                        I sure will> It will probably be next spring as I have quite a bit of work to do but I will hit you up when I get it done.

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