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Post by bdalameda on Aug 5, 2012 1:48:31 GMT -5
I tried an experiment tonight. I have been thinking about the 3000 rpm shudder that occurs under load. My reasoning is that when the engine reaches a cetain rpm a harmonic develops as the engine power impulses creat a torsional vibration and this created a whipping of the primary chain and is transmitted to the drive chain. When this happens the rear sprocket rubber dampers allow the sprocket to accellerate forward as the dampers compress when the chain whips violently. The dampers make the problem worse as they are made of pretty soft material.
I decided to see if I could change the harmonic problem by replacing the sprocket dampers with dampers made of 90 durometer polyurethane. I purchased a .625 thick piece of polyurethane and used a stock damper as a guide and made a set of dampers. I just finished them tonight and took the bike out for a ride. I only rode it for a short distance as it is pretty late here but I seems to have moved the shudder down to a lower rpm and after reching third gear seems to be gone. I need to put some more miles on them though as I just rode for a few minutes. I'll let you know how this works out after I get some more miles on them.
Dan
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t140v
3rd Gear
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Post by t140v on Aug 23, 2023 15:37:31 GMT -5
I know this is an old post but does anyone know if there is any more information on modifying the cush drive on the back wheel and the resulting effects on the grind.
Regards Stuart
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Post by Framitron on Aug 23, 2023 19:48:16 GMT -5
I'm always interested in this topic. The grinding is very out of place for what could be an ultrasmooth bike. I'm thinking that Suzuki would have tasked their engineers to fix that problem if they were to continue production of the bike.
Anyway, I think that one would have to have some means of measuring the amplitude of deformation of the cush rubbers across the rev range and see if it is much worse at the grinding speed. Probably on a dyno with a high speed camera and index marks on the hub and drive.
My personal opinion is that the primary tensioner needs a hydraulic damper in order to prevent the primary (and the final drive) chains from whipping in synchronous. Or a more rigid sliding shoe type tensioner like old Harley or Triumph/BSA/Norton primary drives have.
But the hard cush drive is an easier test so it might be worth trying...
Al
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Post by multistrada1 on Aug 29, 2023 21:36:44 GMT -5
I use a longer than standard rear shock made by ICON and set the chain tension on the tighter side. That seemed to eliminate most of the shudder. Also, now that I have the carb fully sorted its even better.
Before these changes the shudder was very annoying, now I barely notice it.
Hope this helps
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t140v
3rd Gear
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Post by t140v on Aug 30, 2023 17:07:51 GMT -5
New high performance cush drive rubbers arrived today, see what happens when fitted Attachments:
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Post by wayne on Aug 30, 2023 21:14:45 GMT -5
Didn't know these things even existed. Look forward to the report Stuart.
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t140v
3rd Gear
Posts: 422
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Post by t140v on Oct 22, 2023 5:43:30 GMT -5
Didn't know these things even existed. Look forward to the report Stuart. Hi Wayne, So after replacing the primary chain, fitting high performance cush drive segments, and renewing the sprocket carrier and new chain and sprockets (and fitting a SU ) there is still a little shudder, but it now happens at 4000 rpm if in a high gear pulling from 2500 rpm. If its ridden hard through gears then its hardly noticable. Regards Stuart |
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Post by wayne on Oct 22, 2023 17:27:06 GMT -5
Thanks Stuart. Good excuse to replace those 50 year old cush drives.
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Post by multistrada1 on Jan 20, 2024 18:02:00 GMT -5
Do you know if these high durometer cush drives are still available, could not find them.
I was wondering if taming the shudder, might increase the primary chain wear, or reduce it.
I'm thinking more primary chain tension could help, but I'm sure Suzuki engineering did the homework
on this back in the day.
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Post by timpa136 on Jan 21, 2024 11:48:43 GMT -5
Do you know if these high durometer cush drives are still available, could not find them. I was wondering if taming the shudder, might increase the primary chain wear, or reduce it. I'm thinking more primary chain tension could help, but I'm sure Suzuki engineering did the homework on this back in the day. I think they did as well.... and in secrecy. |
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t140v
3rd Gear
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Post by t140v on Jan 22, 2024 4:56:21 GMT -5
Do you know if these high durometer cush drives are still available, could not find them. I was wondering if taming the shudder, might increase the primary chain wear, or reduce it. I'm thinking more primary chain tension could help, but I'm sure Suzuki engineering did the homework on this back in the day. These guys make the rear cush drive rubbers, get the gt750 ones, same as RE5 store.schnitzracing.com/search.php?search_query=sen101 |
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Post by Framitron on Jan 22, 2024 12:28:43 GMT -5
If I remember correctly the Suzuki part number for those cush drive rubbers matches with many of their other bikes including the Huyabusa. That is probably where the demand for aftermarket parts comes from. I guess Suzuki decided that the design was good enough to just keep using for decades.
Regarding the primary tensioner, a number of years ago there was a posting by a group member who added a supplemental coil spring to his tensioner. I believe it helped but did not completely remove the shudder. It would be worth digging up that old post. There was a photograph posted as well.
Would have been great to have been a fly on the wall when Suzuki discussed the tensioner. I wonder if it got full vibrational analysis or if the overworked engineering team just foisted it off to an intern...
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