02 Ural Tourist 750
Denso Alternator (installed before I owned)
Herzog gears (installed before I owned)

I have this weird rattling sound that's coming from the front of the engine (alternator area maybe).
it doesn't happen all the time, only at certain RPM's, since I don't have a tach I can only tell you the speeds
that it occurs at: under normal acceleration in 1st gear from about 10mph to 15mph, 2nd gear from 20mph to 25mph
3rd gear from about 30mph to 32mph and 4th gear from about 40mph to 42mph. It doesn't rattle any other time than
at these RPM's/speed and if you let off the throttle to get the RPM's down it stops.

I hope this makes sense, let me know if I need to try and explain better.

Thanks!

Hard to say without more data.
Initially, a guess would be the timed breather. Sounds like something interesting happened to the front gears in the past. If the timed breather pin (or hole in the time breather) itself was damaged (or elongated), it will rattle at certain RPMs.

what other kind of data could I try to get that might help?

Could it be something that could cause catastrophic damage?

The breather rattle will usually have a "ring" to it as well.
If the breather is loose, it can wear the front case where it fits into and may eventually shear the pin and then no proper crankcase breathing. If you get anxious removing the alternator and probing the breather will usually answer if it is the breather or not.

Use a mechanic's Stethescope, they're available on the web from several sources. Or, "make do" with materials on hand.

A long screwdriver... hold the handle to your ear, and move the tip from site to site on the engine while listening.. it will "point" you to the area that's the source of your noise.



A piece of stiff garden hose can do much the same.



Once you're confident of the area the noise source originates from, the possible causes have been pretty well narrowed down.


Best Wishes
John Panyon

yeah, I have a mechanics stethescope, the problem is that it won't do it just reving the engine up, it has to be under load ie. driving to make the sound.... Which presents the problem of me riding down the road trying to hang off the bike with a stethescope. I hope to get someone to ride with me in the sidecar and listen with the scope while I drive, but haven't got anyone that knows what to listen for yet...

I would have a very close look at the internals of the alternator. My new patrol developed a small buzzing sound...which I dismissed, as it was 'phantom' in many instances. But it only appeared 'under load' and after 25+ km's usually hiway time. A couple of more bothersome soundings, but adding in a bit of electro-mechanical sounds...but still could not be duplicated by the dealer. Eventually the bike seized on the way home, lurched violently to the right and refused to start or turn over, and was hard to even kick over.

Dealer has it now and tells me that the vanes on the alternator..internally...were bent...somehow, either at the factory, or by the heat, and the combination of heat and motion caused it to disintegrate. The ural folks say that this is the first time they have seen this on the new alternators and are looking into it...

If it only happens when the engine is loaded and the noise is DEFINITELY from the front of the engine then I would suspect a crank bearing.

Have a look round the gearbox and drive shaft to see if anything is rubbing?

Has anyone here ever dealt with Lear Unlimited in Muncie, Indiana? Thats where my bike came from originally and it's pretty close to my house, I just am not sure how good they're service/mechanic is. I'm thinking about taking this to an experience Ural person and letting them listen/diagnose to get a good idea of what the problem could be. I'm sure someone actually hearing it will be easier to diagnose it, than me trying to explain it on here. But I appreciate all the input/suggestions so far!

Thanks,
Jake

Is there any change in engine note when the engine is idling and you pull in the clutch?

Not that I can think of, I'll have to give it a try though, never paid that much attention while idling.

Did you ever figure out what was making this noise? This sounds a lot like what my bike is doing. My noise comes and goes and is load related.