New Alternator Bushes Self Destruction

[Vespa no more]

My nuts went nuts...

Triumphantly installed (expensive $38) new alternator rubbers (aka Monkey nuts) ... noises diminished then returned within 3 minutes. Looking closely, fragments of rubber could be seen gathering outside the alternator. Removed alternator and found all rubbers separated and worn or damaged.

Part number used: 12311464877 as per Motobrick / Frankenduck suggestion. Bushes placed in correctly and sprayed with some Armour-all (maybe too much... not sure that this is needed is bushes are carefully placed in the alternator cup). Alternator bolts were all installed relatively tightly (by hand ... but approx 50NM ie firm).

Does one size fit all?

Any ideas anyone?

My guess is that they fell out of position got jammed up and got mangled (a couple of nuts had some 'bite' marks out of them). Probably affirms the use of silicone to hold them in place.

Note:
Alternator will only go one way - there is a section removed from mounting bracket to accommodate starter motor beside it.
Also, to aid alignment of alternator, I penciled a mark on the alternator driver vanes cover and on the alternator cup. Suspiciously went in first go.

Alas...

Let this be a warning to others. Have confessed to a couple of other brain explosions elsewhere ...

I even recorded the noise before replacement to post for those not sure what it sounds like!

[rbm]

Did your alternator drive dog and cup look intact?

The drive dog should look like this:


And the cup like this:



If your drive dog looked something like this:



Then that could be a cause.  Also if you didn't install the bushings as shown in the second diagram, that could also be a cause, but honestly I've never seen that type of destruction occur before (and I've been reading the forums for several years now). The little rubber bits that holds the bushing pairs together have to be oriented deep into the cup; they should not be exposed at the top of the cup.  Examine the second picture carefully.  I can't think that this type of a mistake could lead to the destruction you experienced.

[Vespa no more]

Thanks for the reply.

Both cup and driver are fine. Bushes were installed correctly. Alternator spinning freely.

Sort of reassuring to see the chaos in the second photo - looks like the floor in front of the fire box on a steam train. Clearly the driver and the cup were making contact without any bushes in between.

Guess I will just have to buy another set of bushes and cross the fingers. Might even silicone the bushes in. Question: how does the clip on the back of the alternator come off. Looks like spade connections but mine were very resistant.

regards

Guy

[Laitch]

I even recorded the noise before replacement to post for those not sure what it sounds like!

Please post the audio file, Vespa.

[TimTyler]

Both cup and driver are fine. Bushes were installed correctly. Alternator spinning freely.
...
Guess I will just have to buy another set of bushes

Just to clarify...

Part # 12311464877 is called "Rubber Mounting" or maybe rubber bushing and sometimes "monkey nuts". You need three in a set.

Alternators also have "brushes" (# 12311727756) or Carbon Brush Set.

[Vespa no more]

A suggestion for installing alternator bushes

As mentioned earlier, "my nuts were short lived". On second attempt, made sure I took my time.

Used the blue silastic (RTV?) under rubbers in the alternator cup.
Then spread the rubbers apart to make sure the drive dog vanes would easily slide into place - Basically a folded piece of plastic off a milk container with a small bit of three ply / masonite etc to push them apart.
Let this sit overnight.
Marked position of gap in rubbers and drive dog vanes and the two very easily went together.

Wont be a decade before I do this again and by then I might have forgotten.

On testing, LESS noise but still the low rev rattle in the area - so the output shaft anti backlash spring or the bearings. Nothing that increasing the idle to 1,000 rpm didn't eliminate.

Hope this helps

Regards

Guy

[The Mighty Gryphon]

Nice job with your monkey knutz.  This rattle, does it occur only at low engine rpm's?  Does it have sort of a clank sound to it?

I recently had a similar noise in my K75RT.  It happened between about 1200 and 2000 rpm.   A loud hard metallic clank like a hammer on an anvil that comes out of the back end of the engine near the alternator .  It seems like it is a not uncommon noise for older K75 engines.

On my bike it was caused by looseness between the balancer shaft and the clutch basket hub.  I suspect the problem was the result of oil getting in between the contact surfaces of the two parts, probably when a previous owner replaced the clutch o-ring and rear main seal.

Beyond being annoying, I couldn't see where the noise was indicative of anything that would damage the engine.  It is just a couple of ears banging around in notches in the output gear.  Mine did it for 18,000 miles before I fixed it. 

The next time you pull the transmission to lube the clutch splines, take the clutch apart, undo the nut that holds the basket and with the basket out shoot some brake cleaner into the engine to clean the face of the balancer shaft.  Clean the clutch hub and reassemble making sure to get the proper torque on the clutch nut.  It adds maybe an hour to the time it takes to do a clutch spline lube and you'll have a new clutch o-ring in there as a bonus.  No need to drop the engine like I did, just pull the clutch out.

[Vespa no more]

Rattle limited to below 1000 rpm. Have adjusted cable tensioner (quite a bit) to raise revs). I will do a total restoration on the bike "some time from now" after I have had it on the road.

Main priorities before re-registration:

Speedo not working (have opened the instrument panel but couldn't totally remove the connectors - so just applied dielectric grease and moved them up and down ... no change... also have removed and cleaned speed sensor on final drive (might have wired it in reverse but have been assured it is sinusoidal (whatever that means) and doesn't matter). Got anything to suggest?

Stalling when revved up from idle while still cold. Suspect airleak and will be out with the spray can. Anything else I should be checking. Revs freely when warm.

Front fork slight leak: I have seals to put in but there is very slight pitting. Also because the fork action is quite sloppy, I might just add increments of 10ml of fork oil until it is more acceptable. Progressive fork springs and a replacement staunchion (sp?) would be best.

Australian owners: anyone got a plastic dash (goes over the fairing and under the screen... painfully thin and cheaply made), LHS fork... (annd anything I have forgotten about?)

Regards

Guy

[darthbane71]

So Vespa, you are still having the rattle? I also had a similar noise and replaced the monkey nuts and it got better for maybe a few days before going back to what it was.

I will check out the clutch assy when I go into it next

Sent from my XT1080 using Tapatalk

[Vespa no more]

Still got the rattle.

But if you adjust the screw at the base of the throttle body assembly (the "screw with lacquer on it and is not to be adjusted") and raise the idle to 1000 rpm (the cable to the right adjusts the choke tension and takes a lot of adjustment to raise the revs) the rattle goes away. Just be careful that the throttle cable tension is not too tight that when the steering is in full lock the cable doesn't pull and raise the revs. There is a cable tension adjustment next to the RHS fork lower triple clamp under a black rubber sleeve. There are guidelines / suggestions for tolerances eg. first 2-3mm of throttle to have no affect on revs / cable etc

I am assuming that the motor needs to be dropped out to properly address the output anti-backlash spring, shaft bearing and occasionally the mounting bracket I believe. Far more serious and longer but ... hopefully no rattle. If and when this happens I will do the whole bike, clean the motor / bare metal and repair and paint the rest.

I hate noise on machines. When, in the car, I say to my wife "Can you hear that?" she gets the shits "I hadn't noticed it until you told me!" ... silent treatment for varying durations follows. Mind you she once came home saying "I think the car is making a noise" I went out the front and the front bumper was hanging off the car - one end touching the road (FOR THE SECOND TIME!).

GF