Horrible noise from gearbox(?)

fiatfan

fiatfan

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Now I really need help, soon going totally bananas..... Background is this: completely restored and somewhat upgraded 850 engine, works fine, no problems there. Primary is a new belt drive and dry clutch (complete) from RGM and a new stator. Gearbox have new bearings and bushings, new kick axle. Also a used shell in great condition, found that in the US. There are no rubber mounts, it´s solid bolted in the frame.
The problem is this: As soon as I start rolling, accelerating, there is a terrible grounding and whining from somewhere in the transmission, not a sound that I have to really listen closely to hear, it´s loud! And I also feel it in the bike. It´s fine when the engine is running, standing still, no sound when I pull/release the clutch, put it in gear still no noise, but when I start rolling it imediatly starts making that noise. When I drive and not accelerate, just let it roll and the throttle off, still in gear, the sound dissapears. It´s only when there´s a load on the transmission.
My guess is the box, but what can make such noise, I´m out of ideas. Have had the box apart twice this summer, find nothing wrong in there.
Ideas please, anything!?!
\Tommy
 
Hi,
Have a look at the nut / washer / tab washer which secure the clutch center. I got the same feeling and fear as you when I forgot to tighten the nut enough.
 
Whining might be belt drive. Do you have double adjusters? Angle or not in line belt wheels. Correct tension?
Shell broken between drive side bearings?
Bent shafts? Just guessing.
 
Last edited:
So a continuation from this thread ?

fiatfan

Thread 'Transmission trouble'

Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I...

You best run through all the suggested actions and detail what you found.

fiatfan

Thread 'Transmission trouble'

Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I...
 
Mike40M said:
Whining might be belt drive. Do you have double adjusters? Angle or not in line belt wheels. Correct tension?
Shell broken between drive side bearings?
Bent shafts? Just guessing.
Click to expand...
Double adjusters, belt seems ok in line, doesn´t move. Changed the tension a while ago, think it was a bit tight. Shell is fine, shafts checked and ok. Keep guessing, someone must have the solution! I hope....
 
kommando said:
So a continuation from this thread ?

fiatfan

Thread 'Transmission trouble'

Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I...

You best run through all the suggested actions and detail what you found.

fiatfan

Thread 'Transmission trouble'

Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I...
Click to expand...
Yes, have been occupied by other things so I haven´t had the time I wish I had. The bike has been standing still. I removed one steel plate from the clutch stack, there was two in the bottom, and slackened the belt a bit. But the same result.
 
Must ask this too; can you put the internals in the box in place and install some part wrong, and it would still work? In my mind that is not possible, but I´ve been wrong before..... I just suddenly came to think about the second gears that were changed sometime -73 or 74? Can it be a mix of gears, I´m not certain that I checked that.....
 
To further narrowing your problem, is the noise continuous or periodic? Does it change with revs and/or transmission gear ?
Inspect transmission bearings carefully, try rotating them and feel if there is any resistance. If say one of the layshaft bearings locks up due to a cracked bearing ball, and the shaft starts turning inside the race, it will soon emit a terrible grinding sound. This will show up on the corresponding shaft end of course.

- Knut
 
mdt-son said:
To further narrowing your problem, is the noise continuous or periodic? Does it change with revs and/or transmission gear ?
Inspect transmission bearings carefully, try rotating them and feel if there is any resistance. If say one of the layshaft bearings locks up due to a cracked bearing ball, and the shaft starts turning inside the race, it will soon emit a terrible grinding sound. This will show up on the corresponding shaft end of course.

- Knut
Click to expand...
The noise is constant when I put load on the transm. and it is there on every gear. It follows the revs but the "volume" is more or less the same, maybe more on second than first gear. All bearings are new, I have checked the end play of the layshaft and added the appropiate shims. There is no debris in the box, no visible damage anywhere. That is, for me, the big mystery, there should be something obvious and easily spotted when it behaves like this. I don´t get it.
 
marinatlas said:
Did you check any signs of drive chain rubbing either on gearbox shell or ....? is the sleeve gear bearing a tight fit in the case ?
Click to expand...
No problem with the drive chain, the bearings in the drive side are tight and locked in place. The box shell I bought used was in very good condition.
 
Mike40M said:
More guessing. What in top gear? When all gears in the box has nothing to do.
Click to expand...
Keep ´em coming.... I have not actually had it in top gear more than a very short time, it´s so painful to drive when it sounds like it does. I´m afraid it´s going to go CRASH on me.... But it sounds about the same on the first three gears.
 
1) Does it make the noise if you put bike on centre stand in neutral with engine off and then rotate the rear wheel by hand?

2) Does it make the noise if you do the above, but with bike in a gear and clutch pulled.

Dennis
 

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