January 24, 20179 yr I have a worn out 2003 250cc Beta Rev. When I got the bike, the engine itself was pretty loud - a mixture of a constant loud drone mixed with the occasional loud scraping noise. Imagine the sound of scraping leftovers off a textured ceramic plate with a knife and fork and you will know exactly what I mean! I dropped the gear oil, which was in awful condition and almost empty, and replaced with 550ml of MT75 gear oil. This oil has been in for a few hours and has remained red so the old oil must have been that - just old, rather than any sign of leaking coolant into it. The oil change immediately silenced the intermittent scraping noise, but the motor itself is still very noisy - the noisiest Beta engine I've heard. It's not a knock, it's not a rattle, it's not a tap, it's not even quite a rumble, it's just loud and constant drone like you'd expect from a cement mixer or something. I've tried stethoscoping the engine to track the noise, and it doesn't appear to be top end, it sounds more like it's coming from the clutch/gearbox. It doesn't appear to be affecting performance in any way - the bike accelerates snappily, changes gear as well as I'd expect a 13 year old Beta to change gear, doesn't overheat etc etc. It just sounds a bit embarrassing! Any ideas? If not I may just do another oil change and then just keep running it until something else happens... will try to get a video but I'm away at the moment and the microphone may not pick up the noise properly anyway.
January 24, 20179 yr I have heard one like that and it was bad main bearings from swallowing dirt. You could see if there is up and down play in the flywheel.
January 24, 20179 yr Does pulling the clutch in make a difference to the noise? It's not uncommon for clutches to chatter or rattle.
January 24, 20179 yr Author No, that was my hope but clutch/no clutch/neutral/in gear makes no difference. Neither does increased revs seem to make much difference - it's just always there, which makes me think mains, which is a bit annoying but not the end of the world I suppose.
January 24, 20179 yr Set of main bearings went in my '05 from sitting in storage too long. Sounded like a rock crusher. Bike ran great but I had it fixed before it went catastrophic.
January 27, 20179 yr Author Rock crusher is not a bad comparison actually. I reckon it's the mains. Bleurgh, hadn't planned on tearing it apart but hey ho.
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