SteveBorland
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- Joined
- Nov 15, 2010
- Messages
- 818
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I've just put the bike back on the road after some winter work which involved removing the primary drive and the swing arm and now I have a very strange noise which is puzzling me.
Here's the background:
Over the winter I had the whole primary drive off - its a Maney belt drive, and the belt was rubbing on one of the alternator mounting posts. The swing arm came out as part of the process to use a one piece 17mm rear axle.
No changes to the engine or gearbox. Even though the bike is an 850, it has the 750 clutch setup of 3 plain plate and 4 friction plates. It's not given any problems before, so never bothered to change it.
When I reassembled the bike, the initial startup gave a horrible scraping sound, which turned out to be the clutch hub rubbing on the backing plate. I could press the hub very slightly out against the inner bearing circlip and this solved the problem. No idea why this happened though, no new parts involved. At this point, I decided to replace the 3 steel plain plates in the clutch, the old ones had some corrosion pits on then, but still seem to be perfectly flat.
Now, when I put the bike into gear and release the clutch, I get a quite loud knocking noise, repeated 3 or 4 times as the clutch engages. When the clutch is fully in, the noise vanishes. Repeats at every gear change.
It's sufficiently loud that I can clearly hear it over the engine & exhaust noise.
If I put the bike up on the center stand and engage first, there's no noise as I feed the clutch in, in other words it only occurs under load. I didn't think of trying to load it using the rear brake though.
My first thought it was the lower run of the belt slapping against the primary chain case, but there's no signs of contact on the case or the belt. The belt is just slack enough that I can rotate it 90 degrees on the top run. The knock does not really sound like belt slap though.
Checked the crankshaft nut holding the front pulley & alternator - tight. Removed the clutch plates and checked them, no visible signs of anything there. I wondered if it could be the now dry friction plates slipping against the new plane plates, so I tried replacing the old plates. No change the sound is still there. I read a suggestion that a light smear of oil on the friction plates might help, so I tried this as well, on both the old and new plain plates - no change.
It's possible that the LH exhaust pipe is hitting the primary chain, but then this would occur at all speeds, not just when engaging the clutch.
Tonight I will remove the clutch once again and have a good look around, but I'm rather puzzled, so I'm hoping that someone has an idea?
/Steve.
Here's the background:
Over the winter I had the whole primary drive off - its a Maney belt drive, and the belt was rubbing on one of the alternator mounting posts. The swing arm came out as part of the process to use a one piece 17mm rear axle.
No changes to the engine or gearbox. Even though the bike is an 850, it has the 750 clutch setup of 3 plain plate and 4 friction plates. It's not given any problems before, so never bothered to change it.
When I reassembled the bike, the initial startup gave a horrible scraping sound, which turned out to be the clutch hub rubbing on the backing plate. I could press the hub very slightly out against the inner bearing circlip and this solved the problem. No idea why this happened though, no new parts involved. At this point, I decided to replace the 3 steel plain plates in the clutch, the old ones had some corrosion pits on then, but still seem to be perfectly flat.
Now, when I put the bike into gear and release the clutch, I get a quite loud knocking noise, repeated 3 or 4 times as the clutch engages. When the clutch is fully in, the noise vanishes. Repeats at every gear change.
It's sufficiently loud that I can clearly hear it over the engine & exhaust noise.
If I put the bike up on the center stand and engage first, there's no noise as I feed the clutch in, in other words it only occurs under load. I didn't think of trying to load it using the rear brake though.
My first thought it was the lower run of the belt slapping against the primary chain case, but there's no signs of contact on the case or the belt. The belt is just slack enough that I can rotate it 90 degrees on the top run. The knock does not really sound like belt slap though.
Checked the crankshaft nut holding the front pulley & alternator - tight. Removed the clutch plates and checked them, no visible signs of anything there. I wondered if it could be the now dry friction plates slipping against the new plane plates, so I tried replacing the old plates. No change the sound is still there. I read a suggestion that a light smear of oil on the friction plates might help, so I tried this as well, on both the old and new plain plates - no change.
It's possible that the LH exhaust pipe is hitting the primary chain, but then this would occur at all speeds, not just when engaging the clutch.
Tonight I will remove the clutch once again and have a good look around, but I'm rather puzzled, so I'm hoping that someone has an idea?
/Steve.