Gremlin in the rear end - K-Bikes.com - Excellence in Motion
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post #1 of 15 (permalink) Old Aug 11th, 2019, 6:06 pm Thread Starter
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Gremlin in the rear end

I just purchased a 2004 GT with 29,000 miles a little over a week ago. The tires on it were trash, so I did not do much of a test ride- did hear something in the rear end that seemed 'off', but still felt it was a good enough deal to buy. So I did.

My first thought was final drive bearing- got it home, drained the final drive to look at the fluid- it was very clear. Too clear.... I wondered if metal had been flushed by the previous owner. So, I put fresh fluid in, and drove around a bit. There is something going on. Wish I could describe it well- strong vibration in both foot pegs, and intermittent sound of something rattling in the rear end. At times, the bike is smooth, and then hit a bump, and it carries on for a while. There is a bit of a 'jerk' at very slow speed when I grab the brakes- as though something is moving- I just don't know what.

With about 100 miles on it, I parked it, and started taking it apart- drained the final drive fluid again- very clear, no signs of any metal or pieces. Rotates smoothly, no crunch or unevenness. No oil on wheel or around seal. I did feel a small amount of lateral movement at the pivot bearings, and really thought that would be the issue.

I will point out that the driveshaft looked factory fresh- had some lube on it, but not much. No oil in the swing arm at all. Very, very clean. I could not detect any movement in the swing arm laterally, vertically seemed very smooth.

I replaced the pivot bearings with the Rubber Chicken Garage Bushings, and thought that would take care of it. It didn't. Absolutely no difference whatsoever. I was very disappointed. So, parked again, took the wheel off, thinking maybe I didn't torque the bushings enough. However, still very solid.

The only other abnormal item is the shock- it's an Ohlins, and I have the receipt for a rebuild about 900 miles ago. I played with settings, and when I made it as stiff as possible, there 'might' have been some improvement. I might have imagined it, as well. The connection on the swing arm is rough, though. As though the shock doesn't fit properly, and has worn away some material at the swing arm. The bushing isn't in great shape, but it's not awful. I marked around the mounting point, and took it for a ride, thinking that if there were movement there, the marks would rub off. No indication of movement.

So, I'm at a loss. With the amount of noise, I would think that if it were the final drive bearing, there would be more evidence. I cannot imagine what I'm experiencing is normal for this bike. When I was at speed, there felt like a small amount of drift in the rear end. It did not feel stable.

Any advice? Does anyone think it could be the final drive bearing, despite no evidence? I just don't know where to look at this point. Any suggestions would be appreciated. Thanks.
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post #2 of 15 (permalink) Old Aug 11th, 2019, 6:34 pm
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Did you spin the final drive with the driveshaft disconnected? This will tell you if the bearing is going bad. You will hear a scraping sound and feel a little resistance on rotation.

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post #3 of 15 (permalink) Old Aug 12th, 2019, 7:07 am
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Vibration in the pegs would point at the front U-joint.That is the one that showed wear first on my K1200RS.And actually broke at rather low milleage on my R100GS.

Wear at the shock mount is I'd think somewhat normal.I made some thin nylon washers out of plastic ice cream buckets lids to attenuate that,not perfect as the road grits still get in and the shock rotates a little under compression and wears into the swingarm but the washers help.

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post #4 of 15 (permalink) Old Aug 12th, 2019, 7:17 am
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Quote:
Originally Posted by H96669 View Post
Vibration in the pegs would point at the front U-joint.
That was my second thought. I had a vibration in the pegs just before the driveshaft broke on my 1200RT, but it did last 109K miles.

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post #5 of 15 (permalink) Old Aug 12th, 2019, 6:10 pm Thread Starter
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Hmm... I thought about pulling the swing arm off yesterday, but didn't want to chase a problem without cause. Guess I'll pull the swingarm off and take a look. Thanks for the advice.
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post #6 of 15 (permalink) Old Aug 12th, 2019, 8:15 pm
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Probably a good idea pulling the swingarm if just to repack the bearings.

But I do pull the driveshaft without removing the swingarm.Every year as I have greasable U-joints so has to be done.

Big pair of Visegrips on the end of the DS,then insert a pry bar into the bearing journal hole,buffer the threads with a rag then stick pry bar into the Visegrips and a good yank.....driveshaft should come out.

Reinsertion is a little tricky but a length of dowel rod to extend/hold the DS ,a rag into the U-joint to prevent it from flopping around and then guide it in.Then a good whack on the dowel to engage the circlip and lock the DS in.

Pull rag out then proceed at installing the final drive.U-joints have to be installed "in phase" for longevity so front DS and rear knuckle have to be paintmarked to phase them correctly.

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post #7 of 15 (permalink) Old Aug 13th, 2019, 8:46 am
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"I will point out that the driveshaft looked factory fresh"

Is it the right driveshaft?

Are the driveshaft Snap-Rings doing their job? Are they even present?
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post #8 of 15 (permalink) Old Aug 13th, 2019, 10:23 am
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Quote:
Originally Posted by H96669 View Post
Probably a good idea pulling the swingarm if just to repack the bearings.

But I do pull the driveshaft without removing the swingarm.Every year as I have greasable U-joints so has to be done.
..
....
Pierre, I taught that you were, like me, removing the SwingArm every year to inspect/grease the Clutch Slave.

In the past when my slave had less than 25,000 miles (about 40,000 KM) I would not bother. However, knowing the history of these Magura slaves failure and the consequences, I do it almost every year as preventive measure.

The slave that I have currently is the same I replaced when I did the clutch O-Ring failure job at 54,000 miles (approx 90,000 KM).

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
John (Montreal, CANADA)
K1200RS (2002 IceBlue/Red - 95,000 miles)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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post #9 of 15 (permalink) Old Aug 13th, 2019, 7:19 pm Thread Starter
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Well, I wish I had a diagnosis, but it doesn't seem to me that I do. I pulled the swingarm and driveshaft, but do not see anything painfully obvious.

I checked movement (again) as I removed things, and everything felt solid- no indication the final drive bearing is bad, pivot bushing seems fine, swingarm bearings have no play.

I pushed, pulled, and rotated the u-joints as best I could, and can't feel any movement or stickiness. There is a little bit of grease coming out from the bearings, but nothing that seems unusual.

The only other thing that I am considering is from Bronco's comment- the snap rings are present, and there is a little bit of play from them, but nothing that seems odd. However, the driveshaft part number is not what is listed in the part's fiche. The number on the driveshaft is 26 11 7 660 350. The listed number for a 2004 K1200GT is 26 11 7 663 759.

I can't find any reference to the number listed on the driveshaft with a few minutes on Google, so I have no idea whether it is different, or what the difference might be. Any great ideas on where to look for the part number? I searched Max's and a couple of sites with the OEM parts fiches, to no avail. I also searched random bikes in an effort to find the part, but didn't find anything.

Again, any suggestions are welcome. I have attached a few pictures, in the hopes that more experience from the group will see something that I don't. As always, thank you for the input.
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post #10 of 15 (permalink) Old Aug 14th, 2019, 6:58 am
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Hum....Pinion bearings in the final drive? Might be time to open the final drive and inspect it?Easy to open them up and pulling the crown gear out does free the pinion shaft from the gear pressure and then pinion bearing could be checked for play/roughness.And gear wear marks could give you an idea if the lash is correct.In any case opening them up is rather easy.A little heat cover can be tapped right out and the axle/crown gear will remain with the cover.

Small axle tapered bearing could be bad also?Or loose on the shaft?Not such a rare occurrence I have 2 final drives at home with that problem and both have good big bearings.

It has been a while but I seem to recall a part number change for the driveshaft.The old number may have been dropped off the list by now.I'd have to be home to confirm with my spare which has I think a similar build date code.

Won't be until the mid/end of September til I get back home.In the meantime and for Jean,my slave cylinder is at 250,000 kms.Inspected and regreased every few years but only coincidentally with other jobs requiring swingarm removal.Good grease,compatible with all seals....I wouldn't want to do like the GS guy who grossly overlubed his new slave bearing with some petro based grease that rather quickly migrated to the slave seal and destroyed it.

Good greas....Superlube with Syncrolon,compatible with all types of seals.
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Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53
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