AAU Spring Replacement

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WEM

WEM

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I've been experiencing periodic high idling after my bike warms up. The bike has new (approx. 1,000 miles) Premier Amal carbs and other than the high idle issue is running really well. First kick starts and great acceleration and handling. (I probably just jinxed it by putting that in writing). I had a look at the AAU springs and it looks like one of the springs might have lost some, if not most, of its tension. Based on research on this forum, I think that might be the cause of the problem. I've been lubing the AAU every off season as part of annual maintenance. My question is whether it's possible to replace the AAU springs without removing the AAU from the bike. If it is possible, I'd appreciate advice on the procedure to do so. Thanks.
 
I'd remove the AAU and grease up the sliding slots and lube the felts , replace the condensers and replace the springs all at the same time. This is a high maintenance area for sure. Neglect greasing the advance slots and hang up will occur and wear. The advantage of points AAU system is a perfect advance curve. And avoiding discussions about electronic unit failures.
 
WEM said:
My question is whether it's possible to replace the AAU springs without removing the AAU from the bike.
Click to expand...

Yes. With the points plate and AAU bolt removed the springs can be unhooked. The points cam and bob weights can then be removed and lubricated without having to remove the AAU. Note or mark the position of the points cam so it is refitted in the same position and not 180 degrees out.


Lucas 10CA (late) AAU left, 6CA (early) right.
AAU Spring Replacement



AAU Spring Replacement
 
When you replace the springs, carefully check the the slots on the advance weights to be sure they are smooth. If not, smooth them with a file/400/600 grit wet/dry sandpaper and lube the slot sides with a smear of silicone grease. Buggered slots can cause the weights to hang up in the partially advanced position even if the springs are OK.
 
L.A.B. said:
Yes. With the points plate and AAU bolt removed the springs can be unhooked. The points cam and bob weights can then be removed and lubricated without having to remove the AAU. Note or mark the position of the points cam so it is refitted in the same position and not 180 degrees out.


Lucas 10CA (late) AAU left, 6CA (early) right.
AAU Spring Replacement



AAU Spring Replacement
Click to expand...

And you can see the slot for the pin (lower one in Photo )is already looking worn from lack of Lubrication ?
 
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Thanks for the information. I think I'm getting a handle on how to go about replacing the AAU springs. But I'm wondering how the AAU plate is attached to the camshaft. If the AAU bolt is removed, what is holdIng the AAU plate on the camshaft? Wouldn't the AAU plate just slide off the camshaft?
 
Perhaps the best spring replacement is a Pazon Ignition system. trpouble and maintenace free.
Dereck
 
WEM said:
If the AAU bolt is removed, what is holdIng the AAU plate on the camshaft? Wouldn't the AAU plate just slide off the camshaft?
Click to expand...

No, it's a tapered joint so as long as you are reasonably careful not to 'break' the tapered fit between the AAU and the camshaft when the bolt has been removed then the AAU should remain tightly in place.
 
As LAB said - it's taper fit and should be fine. Usually you have to break it loose with a bolt of the proper size (can't recall what that size is) inserted into the AAU which, when tightened, pops it off the cam.

Assuming you don't mind the periodic maintenance, properly maintained AAU/points is probably the most bulletproof/best performing ignition you can have on a stock Norton. ;)
 
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I dunno, Mike; for a decade my Tri-Spark's been good to me.

When I was young I had the time, didn't mind, rather enjoyed, constantly futzing with points gaps and timing plates and buggered soft screws and timing lights and replacing perfectly good but cheap condensers and greasing bob weights and comparing and replacing springs, and then finally resorting to hard chroming the bob weights, only to learn that I also had a problem with worn/leaky zinc on zinc carburetors and slides.
 
I've been there too, John. Fitted a Boyer when they came out and never looked back. Seems to be some nostalgic romantic allure to the old mechanical stuff today, especially given the reported failures of the electronic ones out there. I still have the points and AAU in a box somewhere, but I doubt I'll ever be reinstalling them.
 
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