Bad Vibrations.

Noticed in the last few days a cyclical driveline vibration, very similar to a chain drive bike with a very bad tight spot.
Symptoms;
1. Mainly felt at low speeds below 70kph.
2. Seems more prominent with higher gear/lower revs.
3. Not detectable with clutch dis-engaged and free wheeling.
4. No CARC oil leaks.
5. C/F wheel hubs/axle inspected and re-tensioned.

Initial thought was universal joint, or maybe CARC bearing, but now I'm contemplating gear box bearing?

My outer alloy wheel hub seems to get quite hot, but carbon fibre wheel does not dissipate heat like alloy wheels.
Also my rear shock is 330mm long, so swingarm angle is greater.

Pull th Swingarm and check the UJ trunnions. That would be my first port of call. The 'Nuovo Six Speeds' both for the win plater and the single plater, are pretty much impregnable.

Pet

Diffs off, rear uni feels/looks ok, gotta buy/make swingarm pivot nut socket.
Don't really want to get the blue and white striped apron out of the tool box.

Ok, Pete gave me the heads up, loosen the two pinch bolts and use a "C" spanner.

Uni joints at both ends seem perfect, the splines were dry as the inside of a Nun's fanny.
There is no visible wear/damage to any splines associated with the drive shaft, but there seems to be more free play (slop) between the output shaft and front uni joint.

What really pisses me off is, the first thing I did after purchase at 17,000km late 2011, was take it to a so called reputable mechanic from the BMW factory. I requested swingarm & steering head bearing re-grease. Paid me money and guess what? Three years and 13,000km later the swingarm bearings look like they may have had the tinniest lick of grease, possibly from the factory. But if he was a BMW specialist why didn't he lube the splines?

Me thinks I was ripped off!

Me too. Pulling the swing arm on a CARC bike is hardly arduous!

Pete

Final outcome, vibration still exists.
Only point of concern was the sloppy fit of the front uni joint to the output shaft.

Pete, would a new shaft alleviate the problem?

Doubt it but I'll lend you my spare to try if you want.

Pete

That might be the easiest way to test the theory Pete.
Any chance of shipping it this week?

If the shaft/uni doesn't solve the problem I will try CARC bearings next.
Or just ride it till the offending bit just breaks ................................

Wayne, when it finally breaks, you will then know which part was crook. Do you know of a good rescue service for bikes in QLD?

I know of a great bloke in QLD, fat lot of good that would do when I'm far away in NSW.

No worries, send me your address again.

Pete

PM sent

Well Pete sent me a little used final drive shaft. While the uni's were tighter than mine there is little or no difference in the loose fit of the female to male splines.

Vibes continue in their cyclical fashion, 3rd gear between 60 & 80 kph seems to be the worst and felt more through the left foot peg.

Decelerating thru lower rpm will send a shudder through the bike, but that is higher than stall speed as it will smooth out before I disengage the clutch. No Tacho so cannot relate to rpms.

Loose engine mounts? Tuning issue? C/F wheel mods? Longer rear shock (330mm) - swingarm angle?

Something resonating? Loose exhaust mount or baffle? Putting the stock wheels back on will eliminate issues with CF.

I'm going to put it all down to tuning and induction harmonics.
With my original tank, mounted up high at the front I would get a knocking sound with light throttle. Putting a foam pad between tank and steering head solved the knock problem. Current cyclical vibes felt through the pegs (left more than right) again came down to specific low RPM/minor throttle and light engine loads. It only became noticeable after changing to the V7 style tank.

Both rear engine mount bolts needed about 180° turn to tighten them up properly. Vibe is reduced considerably. Still noticeable.

Meanwhile fitted a 650lb Eibach spring with a lot less pre-load ...........................

Ha, no account for being a blind old bastard. Checked exhaust mounts the other day, paid special attention to the one mounted under left foot peg, all good.
Today I was swapping out the tail shafts, putting my original in so I can return Pete's loaner.
Saw daylight where I shouldn't, exhaust mount to left foot peg is broken clean thru. Doh!

Didn't I tell you to check your exhaust mounts? But why would you listen to me? I'm a pretentious prick.

I did check my exhaust mounts, with spanners, and they were all tight. Apparently my white cane is too big to find hairline fractures.
And yes, you are a pretentious prick.

ghezzi wrote:

And yes, you are a pretentious prick.

And don't you fucking forget it.





















Merry Christmas












.

I MUST be in the Right Place!!

DungeonMaster wrote:

I MUST be in the Right Place!!

You are.
I know I feel right at home here...

G'day Wayne,

You probably tried this already, but if not, cruise at speed where the vibration is obvious and see what happens when you accelerate then decelerate through that speed. Then, see what happens when the clutch is disengaged, preferably traveling down hill so you can accelerate through or at least hold that speed. Does it vibrate in every gear, same or different speed? You should have pretty good idea wheather it's load or speed related. If you find it's more related to load, the first and simplest thing to check are plugs and leads. If not in good condition, under certain circumstances, they can be temperamental. E.g. If there is to much resistance within the plug or the gap is too big, when the cylinder pressure is high, it may not spark every time. The most common reason is the lead insulation has degraded and allows the spark to hit the narrow tunnel wall instead.
Another idea is clutch, but unlikely after only 30000 km.
You may have considered all these things, I'm just throwing some ideas to keep the pot stirring.

Cheerio

Bugger. I'm a blind bastard. I was thinking about your problem but failed to see that it's sorted. Anyway, I'm glad that you've fixed it.

Actually guys, its not sorted. Rode 600k to get exhaust bracket welded (good excuse to drink some rum). Ran out of fuel twice at about 255km, both times I rolled down hill into a servo. Using 6.3l/100k above 130kph, rough roads but great ride. Dropped to 5.8l/100k sitting 120kph coming home.

Anyhow, cyclical vibes continue thru left foot peg. 60kph, 3rd gear, more noticeable under load (going uphill). Increase speed slowly and frequency increases with engine/road speed. Go to 4th gear and frequency appears to decrease, again giving impression of engine/road speed related, but not the diff.

Just dropped all 3 oils for 30k service. Noticed gearbox has left grey paste on magnetic sump plug.
Engine and diff plugs are clean. Shame I dropped oils into same container. Will continue to ride until something becomes obvious, or next cabal and let Roper San diagnose it.

And then maybe have gear oil lab tested ....................................

Sorry to hear Bella still has the vibes mate.  I definitely felt no such vibes when I rode her before the V7 tank went on.  

Its been wet as down here for the last 36 hrs but may be easing now.  I really don't like running down my dirt rd when its wet - makes an awful mess.  Also noted the Hwy Patrol all over the place since Xmas, so will probably only venture out on the Stone until the double demerit period finishes.