1100 sport vibrations

[Dimitris]

Hi from hot Thessaloniki (37 Celcium degrees- oof)

 

I have noticed, riding my 1100 sport, that when reaching 160 km/h or more, with 5th gear, I sense vibrations that are periodical. In other words, these vibrations come and go with a 2-3 sec time space between them. I feel them all over the bike, from my feet, knees to my hands.

I have discussed this with an old friend (who also rides this model) and he told me that maybe the cause is a false bearing in the shaft or in the gear-box.

 

To exlude a gear-box related problem, I suppose, I have to test if these vibrations are produced also with the 4th gear. If yes, then maybe it means that it is not a gear-box related problem.

 

What are your thoughts? Maybe somewhere else on the bike?

[GuzziMoto]

Hi from hot Thessaloniki (37 Celcium degrees- oof)

 

I have noticed, riding my 1100 sport, that when reaching 160 km/h or more, with 5th gear, I sense vibrations that are periodical. In other words, these vibrations come and go with a 2-3 sec time space between them. I feel them all over the bike, from my feet, knees to my hands.

I have discussed this with an old friend (who also rides this model) and he told me that maybe the cause is a false bearing in the shaft or in the gear-box.

 

To exlude a gear-box related problem, I suppose, I have to test if these vibrations are produced also with the 4th gear. If yes, then maybe it means that it is not a gear-box related problem.

 

What are your thoughts? Maybe somewhere else on the bike?

 

Unfortunately, still doing it in 4th does not mean it can't be a gearbox issue. It would depend on which shaft the vibration is coming from. But if it stops doing it in 4th it is likely a gearbox thing. It might just be a harmonic imbalance (which while not good, may never actually cause a real problem). But then, you should not listen to me as I am not there and have not seen/felt the vibration.

[Guest ratchethack]

Eliminating the easy stuff first, coupla thoughts:

 

Assuming it happens in all higher gears, is the driveshaft correctly aligned with trunnions in the same plane? U-joints still nice and solid when grasping the driveshaft and moving it around?

[Dimitris]

I will have to ride the bike and check what happens with 4th gear. I'll also have to check the U joints as rachetchak indicated.

I will be bach, hoping with good news!

[greenman]

I have this problem to.

It only happens in 5th gear, and only on really flat straight roads, and only between 4pm to 5000 rpm.

The only fault I can find is that there is some play where the rear U joint mounts onto the driveshaft.

I bought another 2nd hand driveshaft, only to find that it was worse than my original.

I've looked really closely at the rear U joint, but I still cannot find out how it is attached to the driveshaft. I know that there are some splines in there somewhere. Other than carefully cutting my spare driveshaft assembly apart to see how it fits together I don't really know how to proceed.

 

Meanwhile, just go faster, that seems to work, or change down to 4th.

 

DD

[pete roper]

Is this bike Carb or Fuel injected?

 

pete

[greenman]

Hi Peter,

Mine is a carb bike.

If I take the driveshaft off the bike, and look closely at the U joint, it only has a wee bit of play in the one plane between the U joint and the shaft. This I suspect is the source of the harmonic vibration.

Like I say, it is only evident when you are riding between 4000-5000 rpm on downhill gradients in 5th gear. And you feel it right through the whole bike.

 

DD

[raz]

I had the same sympthoms, at exactly 4000 rpm in 5th gear, but not at the same [ground] speed in 4th. It was subtle enough I only sensed it wearing ear plugs. It disappeared when I replaced most bearings in the gearbox but I'm not too sure it was actualy a bad bearing, it may have been just some kind of harmonic and not too serious. I've heard of several others sensing this too

 

The above was the straight cut stock gearbox. Nowadays I have a Centauro gearbox on my Sporti. It has better ratios for my cruising needs (even more so as I switched to 60 profile rear) and it has helically cut gears so now I can actually hear the engine

[pete roper]

Hi Peter,

Mine is a carb bike.

If I take the driveshaft off the bike, and look closely at the U joint, it only has a wee bit of play in the one plane between the U joint and the shaft. This I suspect is the source of the harmonic vibration.

Like I say, it is only evident when you are riding between 4000-5000 rpm on downhill gradients in 5th gear. And you feel it right through the whole bike.

 

DD

 

As with all Carb Sports I strongly advise taking the box out and inspecting it. replace the input and output shaft bearings with AC3's and replace 5th gear with the helically cut set off another bike. If any other of the gears are toast get another box, it's cheaper than trying to rebuild a Sport C box.

 

Pete

[Dimitris]

As with all Carb Sports I strongly advise taking the box out and inspecting it. replace the input and output shaft bearings with AC3's and replace 5th gear with the helically cut set off another bike. If any other of the gears are toast get another box, it's cheaper than trying to rebuild a Sport C box.

 

Pete

Mine is the injection 1100 sport. Is there any difference Pete?

[pete roper]

While some of the Sport i's had the straight cut box the big difference was that they had a cush drice in the rear wheel that was missing on the Sport c. This is usually sufficient to protect the gears but if you have any doubts I'd take it out for a looksee anyway. They still have the crappy 3205-ATN9 bearings in.

 

Double check your driveshaft alignment and the UJ trunnions for play as well.

 

Pete