Author Topic: auto advance question  (Read 1131 times)

Offline mike667

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auto advance question
« on: 17.05. 2010 23:58 »
Hey gang
 so while/ when trying to adjust the magneto / timing i notice that after i tighten up the bolt securing the auto advance unit to the magneto the auto advance springs doesn't  snap shut -  seems like its sticking so wondering if i can something mucked up while tightening it down (it closes up fine when off the spindle etc)

any thoughts?
 thanks as always!

mike

Online bsa-bill

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Re: auto advance question
« Reply #1 on: 18.05. 2010 08:34 »
HI Mike - glad you asked this one as my project does the same, I swapped the AAR unit with one off my flash that I know works - no change, so I'm thinking the problem maybe lies with the Maggie shaft ???? maybe
Possible it might free up with use.
Looking forward to to some answers

All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline MG

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Re: auto advance question
« Reply #2 on: 18.05. 2010 10:46 »
Hi Mike and Bill,

I also noticed that on mine,  I think this is caused by the friction in the magneto shaft (mainly points, magnetic field, maybe bearings).
Once mounted, the pinion can't trun freely anymore naturally as it is engaged with the other pinions down to the crankshaft, and the maggy shaft is held by friction (if it wasn't, you had no chance of mounting the AAU I guess).
Just turn the engine over a bit and you will see the AAU closing almost immediately. When I checked timing I also saw it working properly, so nothing to worry about.

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Offline Rusty nuts

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Re: auto advance question
« Reply #3 on: 18.05. 2010 11:22 »
Me three!

I switched to one procured from evil bay.
Still sticks, but not as much as the first which leads me to suspect units themselves rather than magneto shaft.
Also my mag newly overhauled by Dave Lindsay so doubt prob there.

Both seem to work fine & no performance difference between them.
But then my poor old longstroke is still struggling to get past 50 mph but that's another story!

Rusty
1949 A7 Plunger
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Offline mike667

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Re: auto advance question
« Reply #4 on: 18.05. 2010 12:09 »
Hi Mike and Bill,

I also noticed that on mine,  I think this is caused by the friction in the magneto shaft (mainly points, magnetic field, maybe bearings).
Once mounted, the pinion can't trun freely anymore naturally as it is engaged with the other pinions down to the crankshaft, and the maggy shaft is held by friction (if it wasn't, you had no chance of mounting the AAU I guess).
Just turn the engine over a bit and you will see the AAU closing almost immediately. When I checked timing I also saw it working properly, so nothing to worry about.

Cheers, Markus

Markus as per usual you are the man - thanks!

Offline Triton Thrasher

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Re: auto advance question
« Reply #5 on: 18.05. 2010 12:25 »
Check that you have backlash between the teeth of the two pinions.  Lack thereof can cause the stiffness when you tighten the nut.

Offline beezalex

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Re: auto advance question
« Reply #6 on: 18.05. 2010 16:47 »
Guys, as far as I know the sticking is normal, mainly because of brush and cam follower friction.  When the mag is rotating, the cam ring shoe friction always tends to make the AAU retard until the centrifugal force is high enough to pull the weights out.  IOW, don't worry, unless it's stuck tight.
Alex

Too many BSA's