Bearing nois from engine or ?

[bmo]

I have a sound that sounds like a defective bearing. At startup and idle I hear a slight sound. By increasing the speed, the sound disappears. At load, the sound comes at about 1500 rpm and disappears at about 3000 rpm
With an increase in speed, the sound increases, but decreases with less throttle. By heavier driving, uphill increases sound and decreases downhill. Have tried to test if there are variables at different gears without finding any pattern. The bike has recently passed 125,000 km (about 78,000 miles). I have only owned the bike for a few weeks so I am not yet very familiar with the construction of this bike.
I have tried to listen when the motorcycle is on the main support and feel the sound coming from the front of the motor but is not safe. The previous owner says that register belt was recently changed.
Receives all useful tips with great pleasure.

With best regards

BM
norway

[ct1500]

The intake AIR hose at bottom right front of air cleaner box if not connected will cause a rumbling or gurgling sound more or less with the intensity under your observation and description.

[Charlie1Horse]

I'd check the timing belt idler/tensioners. Especially if the timing belts have not been changed. You can take the timing belt covers off and use one of those cheap Harbor Freight stethoscopes to check for noise on the tensioner brackets.
Russell

Those who say it cannot be done should try not to interrupt those who are doing it.

[bmo]

Thanks for the tips, went home from the cottage today and picked up stethoscop and searched for sounds. Found only normal sounds from front of engine and gear. But dynamo sounds disturbing. Disassembled this and checked -ok. However, bearings in the gear housing had longitudinal slots. From a bicycle hose I made 2 mm shims and placed between the rubber dampers and the bearing housing, so far it seems promising. It's over midnight here in Norway, so there will be a test trip tomorrow

To communicate with you on the forum I use translator, as my English knowledge is a bit rusty. So kindly ignore grammatical errors.

Regards

BMO

[CrystalPistol]

Loose t belts will flop flap at low speeds … old, hardened & shrunk alternator drive rubbers will rumble too.

[bmo]

I had a test trip yesterday. The noise was gone, the bike was almost like new, but now I hear other sounds
Is there anyone who knows how much slack it should be in the longitudinal direction of the coupling to the alternator?