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Opinion on bevel gear noise please

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    Opinion on bevel gear noise please

    I was out for a ride a few weekends ago when I heard a gawd awful racket form around the transmission. Stopped and found when in neutral but when on centre stand in gear it wasn't pretty. So spent $400 on getting a truck ride back home (approx 80 miles).

    Did some thread searching and concluded it was likely the bevel gears at the shaft to gearbox union and had a read up on it.

    As luck would have it, I had the spares needed from the parts bike that came with the original bike purchase. (Since stripped right down to parts).

    I concluded that there was no way that I had the confidence, skills, tools or patience for the job so set about finding someone who could do the job. None of the bike shops were keen so I settled on a mobile mechanic who comes highly recommended.

    He arrived last week and spent a couple of hours sizing the job up and was initially pessimistic and suggested the that the engine would need to come out be pulled down and rebuilt and that it would cost thousands. He was very surprised that I had the needed parts and I gave him a print out of all of the thread info which I had found in my search. He had a read then decided that maybe it was something that could be done. the following week.

    Yesterday he arrived and managed to pull the wheel and swing arm off then demount the engine. I bought some work home to do (so I could earn $ to pay him). He found the bolt connecting the shaft to the bevel gear assy had sheared and that subsequently the free movement had resulted in the bevel gears eating each other out. He/we had a pig of a time getting the side mounted bevel gear out (after the shaft bevel assy was removed). Even loosening the case bolts it took about 2 hours of levering and driving to get the sucker out. The side mounted bevel gear was severely munted (see photos).

    He gave the housing a good rag clean and started reassembly. I raised the issue of backlash and he responded that he was confident that the existing shims would be ok (as the serial number of the motor the replacement gears came from was sequential to that of motor in this one).

    He got it all back together just on dark then started it and ran it in gear on the centre stand and it sounded ok. Then he took it for a test run just before the rain came down and pronounced that she was all good to go and gave me a bill for $760 (paid).

    I started her up on centre stand and popped her in gear this morning and can hear some worrying clacking noise. I videoed and up loaded to the link below (along with a couple of pics of the munted gears) I suspect that some of the damage to the bevel gear was as a result of the beating it took while I was levering and he was driving it out with a hammer and long steel rod.



    Can I please have your opinions on the noise and whether I should ride her or strip her down and set the backlash properly.

    Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.



    #2
    Collin,

    I hear what your talking about, what RPM was it idling at when you shot the video? I have had mine make a similar noise in gear, at idle but not that bad. There is some gear lash in the drive system that is normal but that sounds excessive. I would definitely check the lash in the secondary drive to be on the safe side. There is a procedure in the service manual. And make sure you clean out that area, you don't want any loose metal and garbage back there causing trouble down the road.

    Good luck

    Comment


      #3
      Originally posted by bbjumper View Post
      Collin,

      I hear what your talking about, what RPM was it idling at when you shot the video? I have had mine make a similar noise in gear, at idle but not that bad. There is some gear lash in the drive system that is normal but that sounds excessive. I would definitely check the lash in the secondary drive to be on the safe side. There is a procedure in the service manual. And make sure you clean out that area, you don't want any loose metal and garbage back there causing trouble down the road.

      Good luck
      Cheers. She was idling about 1000rpm and I wound it up to around 2000 for a few seconds in the video (which did quieten her down)

      Comment


        #4
        Originally posted by Colin Green View Post
        Cheers. She was idling about 1000rpm and I wound it up to around 2000 for a few seconds in the video (which did quieten her down)
        Yes, at a 1000, that doesn't sound normal, and I'm assuming it didn't sound that way before the breakdown.

        I would have your wrench pull the drive shaft and check the lash.

        Comment


          #5
          Colin, Have you rode the bike yourself yet? how did it sound on the coast and drive side of the gears (on throttle and letting off) did it make any gear (whining) noise? if it did, at what ground speed did you hear it?

          Leave the bike on the center stand, put the transmission in gear and leave the engine off. How far will the wheel turn rotating it clockwise and anti-clockwise? The reason for my asking is to find out how much play there is in the drive line, if any. If I recall correctly my 1982 '850 would turn some where around 50mm stop to stop. If the slop in the drive line is excessive, it 'could' be telegraphing the noise from the final drive or clearance between the driven gear and the wheel spline.

          Off hand the noise doesn't appear to be correct, but it might not be from excessive backlash in the secondary drive assembly.

          Or it could just be something conspiring again'st you...
          De-stinking Penelope http://thegsresources.com/_forum/sho...d.php?t=179245

          http://www.thegsresources.com/_forum...35#post1625535

          Comment


            #6
            Originally posted by rustybronco View Post
            Colin, Have you rode the bike yourself yet? how did it sound on the coast and drive side of the gears (on throttle and letting off) did it make any gear (whining) noise? if it did, at what ground speed did you hear it?
            I will take her for a spin in an hour or so and confirm.

            Originally posted by rustybronco View Post
            Leave the bike on the center stand, put the transmission in gear and leave the engine off. How far will the wheel turn rotating it clockwise and anti-clockwise? The reason for my asking is to find out how much play there is in the drive line, if any. If I recall correctly my 1982 '850 would turn some where around 50mm stop to stop. If the slop in the drive line is excessive, it 'could' be telegraphing the noise from the final drive or clearance between the driven gear and the wheel spline.
            Just checked and yes, it's a lot more play ... 65mm at the perimeter of the tyre (maybe twice as much as before)

            Originally posted by rustybronco View Post
            Off hand the noise doesn't appear to be correct, but it might not be from excessive backlash in the secondary drive assembly.

            Or it could just be something conspiring again'st you...

            Comment


              #7
              Ok, just took it for a spin. There is noticeably more backlash when throttling off, but no discernible noise (whine or clacking) when under power or throttling off through the gears. Though even with helmet off, the wind noise made it impossible to hear anything over about 25 mph anyway.

              Thing that worries me is that I didn't hear anything prior to the last few hundred metres when the old bevel gears died..

              I spoke with my mechanic before taking it for a ride and he was very defensive. He said he couldn't hear any noise on the video (I gave him the link). He said if the backlash wasn't right it would take hours, maybe even days to get it right . Told me off big time for running it in gear on the centre stand (even though he did that himself last night before taking it for a test ride ) He said I should never ever do that as it stuffs it big time. He also said that backlash only needs to be adjusted if it whines (prolly thinking... like its owner). He said to ride it and not to worry, "its sweet".

              He did ring back and leave a message when I was out riding it around the block, to say to give him a call and he will come have another test ride and look at it if it was making noises on my test ride. Guess he is off the hook, though my confidence in him has diminished somewhat.

              I dunno, my gut feel is that it isn't good, but I don't know whether it is a big enough problem to justify pulling it down again, particularly given that he isn't keen and I don't know of anyone else who is either available or up for it... and the cost is a pain

              I think I will keep my fingers crossed and hope for the best.
              Last edited by Guest; 06-21-2013, 11:29 PM.

              Comment


                #8
                Originally posted by Colin Green View Post
                I will take her for a spin in an hour or so and confirm.

                Just checked and yes, it's a lot more play ... 65mm at the perimeter of the tyre (maybe twice as much as before)
                I'm glad you paid attention to the play in the wheel before hand. While it was apart, did you happen to look to see if there was any wear to the spline on the final drive and the wheel? If there wasn't any then we can be 'almost' certain the increase in the wheels rotation is attributed to an increase in the secondary gears backlash. There still could be some wear attributed to the drive shafts u-joint which can be easily checked when the final drive and the boot covering the shaft have been removed.

                Now on to the problem at hand. It is my opinion that this problem needs to be investigated a little bit further. You noticed a noise, which to you, seemed excessive enough to warrant bringing it up to the members of this board. That in it's self is enough to say to me something is amiss with the secondary drive assembly. The knocking noise and the increase in drive line play makes me think that the backlash is excessive, which 'should' have been checked while it was being re-assembled, along with checking the wear pattern on the drive and coast side of the gear teeth. That would have saved the hassle of tearing it apart again.

                The good news is you didn't notice any noise when out on a test ride. That makes me think the gear tooth contact pattern is somewhere in the ballpark, BUT it still needs to be checked just for piece of mind. Reducing the backlash is a simple matter of changing the shim on the driven (output shaft) gears housing for a thinner one. Well, at least after all the the things necessary to get at the driven gear assembly are removed and the bolts on the case are loosened up enough for it to come out (if needed).
                Last edited by rustybronco; 06-22-2013, 12:52 AM.
                De-stinking Penelope http://thegsresources.com/_forum/sho...d.php?t=179245

                http://www.thegsresources.com/_forum...35#post1625535

                Comment


                  #9
                  Originally posted by Colin Green View Post
                  and I don't know of anyone else who is either available or up for it... and the cost is a pain
                  Have you misplaced your mirror sir?
                  De-stinking Penelope http://thegsresources.com/_forum/sho...d.php?t=179245

                  http://www.thegsresources.com/_forum...35#post1625535

                  Comment


                    #10
                    Originally posted by rustybronco View Post
                    Have you misplaced your mirror sir?
                    Hang on I'll just check.

                    I see. That isn't a pretty solution either

                    Your advice makes good sense but I'm going to have to think about it for a while.

                    Thank you very much for your time and advice.

                    Comment


                      #11
                      These bevel gears are made as a set- and kept together so variations in machining/grinding are minimal. But installed in housings, new variations pop up as housings aren't all identical, so the rotating the output housing to one of 4 spots and fitting shims are required to attempt to reduce the tooth contact error. Putting in another gear set would require further shim fiddling to get good loading plus quiet running. I hate to be the poor guy who spent his day at the suzuki factory doing this work.
                      1981 gs650L

                      "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

                      Comment


                        #12
                        I'm not an authority on this but I have been in the same spot and fought my way back to the street. The mesh depth between the gears could be too light, (they are too far apart); or a bad bearing is causing slop in the rotation. Study the factory manual. Either way it will likely chew those gears up again soon. There are shims between the chunks and the case that set mesh depth and shims on the shafts to set bearing preload. Its a PITA to get these right! It took me a lot of patience and trial and error to get these key values correct. If you do it yourself and fix it you will feel like Superman though. Good Luck

                        Comment


                          #13
                          this thread may help: http://www.thegsresources.com/_forum...d.php?t=200119
                          2002 bmw r1150gs 1978 gs1000E skunk les pew 1979 gs1000L dragbike
                          82 gs1100L probably the next project
                          1980 gs1000G the ugly 1978 gs750E need any parts?
                          https://m.youtube.com/watch?v=m_m2oYJkx1A
                          1978 gs1000E skunk #2 RLAP
                          https://live.staticflickr.com/65535/...2f1debec_t.jpg

                          Comment


                            #14
                            Which set of shims did he use ? Usually use the set that came with the replacement gears.. With no load and running in gear it will probably be noisy. With the gears installed Check the backlash by turning the drive shaft flange it should have a very small amount of play.010-.020
                            Last edited by Guest; 06-23-2013, 12:24 AM.

                            Comment


                              #15
                              Originally posted by matt1100 View Post
                              I'm not an authority on this but I have been in the same spot and fought my way back to the street. The mesh depth between the gears could be too light, (they are too far apart); or a bad bearing is causing slop in the rotation. Study the factory manual. Either way it will likely chew those gears up again soon. There are shims between the chunks and the case that set mesh depth and shims on the shafts to set bearing preload. Its a PITA to get these right! It took me a lot of patience and trial and error to get these key values correct. If you do it yourself and fix it you will feel like Superman though. Good Luck
                              I'm still mulling it over. I guess I could do it by feel and tape measure. (I haven't got the right sort of mountable measuring dooda. I think I'll ride it a bit more and keep a real good ear tuned to it and see if it gets worse.

                              Thank you for your helpful advice.

                              Comment

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