Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

crankshaft/rotor repair Gs500

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Bigjula, Sep 11, 2011.

  1. So I was having trouble starting my bike. I could clutch start it but it was just wizzing if using the electronic starter. Took it to a mechanic who promptly said I needed a new starter clutch. $600 parts and labour. Ummm cant afford it sell me the starter clutch and I'll do it myself. I'm a little handy but have the manual and feel that diagnosis is half the battle. So I got the cover off. As I was removing the rotor bolt it just came off. I had been prepared for a fight as the manual says you need a special tool as the rotor is on a tapered crankshaft. Anyway it just came off. Here is what the crankshaft looked like.
    Inside the rotor looks just as chewed up. Can I somehow sand, grind put a paste or something these so they will grab. I threw it all back together and tightened the rotor bolt real tight but it appears that it wasn't enough as the battery is not charging and I can't start it again.
    I checked the starter clutch it's fine. $200 wasted there. 400 saved.
    Cheers for any advise.


    Attached Files:

  2. Was there a woodruff key in there?? (channel on the other side of the crank)

    This is what I would do if it was mine.
    Clean it up the best you can, and the inside of the rotor.
    when its really nice, grab some valve grinding past and rotate the rotor back and forth on the crank. The idea is to get as near a 100% contact between the rotor and the crank as you can. you will be able to tell how good it is by the finish on the crank.
    Heavy duty loctite, Not thread sealer but either stud or bearing mount. Fit stator and use a torque wrench on the bolt. Use your new starter clutch cos if this doesnt work it will be a pain to undo. Leave it till the loctite has set. Cross fingers and see if it starts.

    Things other people have done.
    Buy a new/used rotor with a good centre if yours is U/S. Make sure the crank is clean.
    Weld the rotor on.
    Over tighten the bolt and snap it inside the crank.
    • Like Like x 1
  3.  Top
    • Like Like x 1
  4. Wot foot69 said. I've done the grinding paste trick on similarly buggered tapers and had excellent results.

    Two things to be aware of:-

    As the taper grinds away, the rotor will sit further onto the crank. This probably won't be a problem, but just make sure that it doesn't go so far back that it fouls on the case and that the retaining bolt still seats on the rotor and not the crank nose.

    When you've finished, clean all the grinding paste out of the taper and the surrounding area. Then clean it all out again, and a third time for luck. Most obvious reason is that grinding paste in the oil is not good for engines, but the other reason is that even a single speck of grit in the taper will prevent your nice newly ground faces from seating properly and you'll be back to square one the moment there's any load on it.
    • Like Like x 1
  5. As above, but I'd probably start with a strip of wet and dry.

    Then the Loktite catalogue is your friend.
  6. Cheers for the replies.
    I will be following the instructions pretty much to the word and using the product suggested. I'm hearing you on getting all the grinding paste out can't imagine the damage that could cause floating around in your oil. Will post photos of the process and let you all know the results.
    Thanks again.
  7. Be careful, you dont want to damage the crank any more than it is already..
  8. One more thing. I'm still not clear whether there is/was a key in there. If there is, the edges of the keyway (the slot the key fits in) are highly likely to be skagged and standing proud of the surface. Before doing anything else, any such burrs and edges should be treated to a few strokes of a file to take them back level or the grinding won't work.
  9. I didn't see any key or slot but it may have disintegrated. Haynes manual makes no reference of it in removal or installation of alternator or starter clutch. Something does seem to have done some gouging in there though. I do keep my oil pretty clean with regular changes.

    I will try to get both surfaces it as smooth as possible whilst removing minimal material.
    File, wet and dry, and grinding paste will all be available for use as deemed appropriate.

    I am wondering how this might occur? What would cause the rotor bolt to simply loosen on it's own? 24000 on the clock, 5yrs old? I did by it second hand and had been dropped. And I dropped it, low speed, a couple of times. Maybe I just answered my own question.

  10. Unless something has impacted the end of the crank or rotor its doubtful a drop would cause it.
    Sometimes they just come loose. Loctite on the thread when you reassemble, and torque to specs it should be fine. Threadlocker or the recommended one from the manual on the bolt. The higher grade one on the crank.
  11. OK. Job done on the weekend. This is what I did.

    I started with the wet and dry on the crankshaft. Maybe 20 min with I think it was 180 then 20min on the inside of the rotor. Didn't get rid of all the grooves two of them were pretty deep and I didn't want to take that much off. The loctite 660 recommended said it can handle gaps of 0.5 mm so I though it would be ok. About 10min on shaft and rotor with 400 wet and dry. Got some valve grinding paste from supercheap. course and fine, used both in that order. Sprayed the hell out of it with brake cleaner.

    I couldn't get the starter clutch gear off the rotor. Those socket screws would not come out. I couldn't budge one of them. So I just replaced all the springs, pins and rollers in the starter clutch. Sprayed the hell out of the parts with the brake cleaner, let dry. Spooged the 660 on the shaft and rotor and twisted on.

    Moment of truth. spooged loctite threadlocker medium strength on rotor bolt and inside shaft. Screwed rotor bolt on. I had a big "Snap-on" torque wrench to get it to the 110-130 Nm. The hayne manual says to secure the crankshaft by sticking in gear and putting foot on back brake. I got the wife to help with this. I could not for the life of me get the torque up to that. I could fell the compression resisting kind of bouncy resistance then release. I think the clutch must have been slipping? It says you can use the flats of the rotor to secure but then your not really securing the shaft. my spanner was to wide for the flats anyway.
    This is a bit dodgy. I stuck a spanner through a hole in the starter clutch gear and rested on a mold ledge in the block behind it. Gave me just that little bit extra torque. Didn't get to the recommended but it's bloody tight. Closed it back up and let it set for the night.
    Next day started fine. Took it for a local ride and it started losing power again. Wasn't recharging so must be slipping again. I thought it was stuffed again nothing had worked. Went back in sat down thinking I gunna have to get rid of it for next to nothing....... remembered that I hadn't reconnected the alternator. hahaha.
    Went out, connected it up and took a bit of a longer ride.
    Tried starting it up again..... nothing... what now. this time nothing was happening no wizzing or anything. read the manual and says to start with the the starter circuit. First check clutch and footstand switches. Shorted the clutch switch and went every time. The after market levers I have have a slightly different recess for the clutch switch that make it not work properly. turned it around. Now works every time and I don't have to pull the clutch everytime to start it anymore.
    Anyway we''ll see how long it lasts. I hope it is for good.
    Thanks again all who have offered advice. Especially the valve grinding paste and loctite 660 were perfect for the job.
  12. A tip for locking your crankshaft if you haven't the correct tool.

    Take a spark plug out and edge the engine round until the piston is coming up on the compression stroke (this is critical on a four-stroke. The valves must be closed as the piston reaches the top of its stroke. Getting it wrong can bend valves). Find a length of (clean) rope that fits down the plug hole. Tie a knot in one end so you can't lose it and feed the other end down the plug hole. Turn the engine so the piston comes up and compacts the rope into the combustion chamber. Hey presto, the crank will now be locked solid in one direction.

    Once you've done the tightening/loosening, the rope can be released and pulled out.

    This trick will also work to allow you to change valve springs without pulling the head.
    • Like Like x 1
  13. Thanks for the update Bigjula
    I've never tried that way Pat, heard about it.
    You can also get plastic plugs that screw into the sparkplug thread that stop the piston from going up any further. I think I'd prefer using the rope as it spreads the load around on the piston crown..
  14. I learnt it as an MZ owner too poor to afford the special tools :D. It's fairly kind to your engine and certainly safer than levering off random bits of crankcase.
  15. Hopefully it'll hold. Otherwise I'll be getting out the rope. For the engine I mean. ;)
  16. Okay. So I think I found the root of the problem. Dunno if it should be a new thread but I'll chuck it in here as its related.

    I had been having trouble with the engine when running. Brief losses of power. Took it to a mechanic who said the carbies were dirty, sounded reasonable but a mixture screw was stuck so any more problems carby will need to be replaced. Got it back worked fine. I asked them to do the valve clearances as I did my own last service minus the valves. $600.

    2 months later chugging started again. Looked in the tank saw some rust. Decided to Kreme it. Actually used the KBS system. Cleaned out carbies. Went to unscrew the float bowls and stripped the screws. Weren't these just done two months ago? I reckon they just drained them. pfft. Never again going there. Cleaned the jets and all other orifices.Put it all back together. worked for a little while then started again. I have not got thousands to waste on a GS500. Thought the mix must be out. tried easy out on the mix screw. ruined it. Got a carby from a wreckers $200 and chucked it in. Still chugging. Pulling my hair out at this stage. Then the no starting and no charging started happening. I fixed that as discussed above. and still chugging.

    Took it to another mechanic told him all the problems he said it must be electrical. So went back to the book. 1st check ignition circuit. Start with clutch switch (been there) check kick stand switch. I remember spraying the kicktand with a bit of inox when going over the bike once, now it is quite loose up top. tied it up for a ride with coat hanger, no chugging. I don't believe it. The problem the whole time.

    I think this is what loosened the rotor bolt. High revs go over a bump or whatever and cut out due to kickstand switch. All the angular momentum of the rotor and the crank stops briefly. Holy %#*$.
    What is this switch for? If you cruising along and decide to put your stand down the bike will stop for you? This idiot switch and the one on the clutch...overkill. Were there really that many accidents when these switches were not included. Maybe if your not smart enough to put the bike in neutral or pull the clutch you should not be riding? Making these things idiot proof puts more idiots on the road?

    Anyway. What should I do. Stiffen kickstand up with a washer or something, bolt a magnet on the frame to hold the stand right up, short the circuit, compress switch with a cable tie or something...?
  17. You are completely correct. The sidestand switch is there for idiots that can't remember to put the sidestand up before riding off. If you are too stupid to put the sidestand up before riding off, you deserve every thing you get. Perhaps motorcycles are not for you. In my opinion.
    The clutch switch is there for idiots that try to start the bike while it is in gear, and on the sidestand. Once again, the better option would be for nature to take its course, and discourage f#ckwits from having anything to do with motorcycles. Once again, the rest of us normal people have to pay the price for the retards amongst us. Sigh.

    PS I just strip all the unwanted electrical crap off my bikes, bridge the wiring to suit, and ride off happily without worrying about stupid shit happening. And I haven't died yet. Even after 26 odd years of riding these illegal bikes.
  18. +1 to roarin's comments. These switches are very easy to bypass if you have a quick look at the wiring diagram. If you don't have the diagram, look on gstwins.com . Everything you need to know about GSs and a lot you don't!

    OK, Ok I'll look it up.....
    Somewhere under the seat is a relay with an orange wire, an orange/blue wire and a green wire. This is the sidestand relay. Take it off and throw it in the bin, connect the orange wire to the orange/blue wire and you can now ride off into the sunset with your stand down. If you also want to by-pass the clutch switch so you can start it while picking your nose with your left hand, just pull the two wires off the bottom of the clutch lever bracket and solder them together.
  19. the new Kiss list for any problems.

    disable clutch and sidestand switch
    check fuel.
    check spark.

    And a sidestand switch is a better idea than the auotflipup sidestand they used to use on some bikes.
  20. The autoflipup didn't leave you stranded when a relay died.