Author Topic: Automatic advance unit  (Read 323 times)

Offline Spow11

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Automatic advance unit
« on: 31.03. 2019 22:26 »
Evening me again  ;)
I've had the magneto refurbished and rebuilt the ATD. Now with the ATD not installed it goes from advanced and back just fine. But when installed on the magneto shaft it is reluctant to go to un-advanced position. Its just on the cusp. After checking the magneto spindle is a bit stiff. I'm wondering will the newly reconditioned magneto bearings free up a little and the ATD will operate as it should?

Thanks Steve 

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Re: Automatic advance unit
« Reply #1 on: 31.03. 2019 22:33 »
Does it return to the retarded position if the engine is turning over?

If so, you may not have a problem.

Online JulianS

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Re: Automatic advance unit
« Reply #2 on: 31.03. 2019 22:43 »
When installed on the engine and engine static those little springs are not strong enough to move the weight of the armature, friction in the bearings and oil seal, the points on the camring, the earthing rush and the magnetism in the body, but kick it over and it should return to retarded. As TT says you may not have a problem.

Online duTch

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Re: Automatic advance unit
« Reply #3 on: 01.04. 2019 00:07 »

 Also, see if it frees up when you back off the nut a tad or ten, and if so, maybe the spindle/spigot is not quite long enough (gear too fat)
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline Swarfcut

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Re: Automatic advance unit
« Reply #4 on: 01.04. 2019 09:07 »
 Steve...  As duTch says, check the back of the fibre timing gear is not binding against the crankcase. Providing the ATD unit freely returns before being mounted, that's fine. As mentioned, the return springs are not strong enough to rotate the magneto armature, once the unit is fitted.

 Swarfy.

Online duTch

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Re: Automatic advance unit
« Reply #5 on: 01.04. 2019 09:48 »

 
Quote
Steve...  As duTch says, check the back of the fibre timing gear is not binding against the crankcase. ..............

 No- that's actually not what I meant, but do it anyway because mine did interfere and I had to carve about 20-30 thou off the casing....what I was referring to is under the nut where I think is a 'C' washer, and where the fibre gear complete rotates on the spigot/spindle/shaft, this- which if not protruding, the gear assembly may bind.....I also may be dreaming as I don't have one to look at just now ; *idea* I do have one but not here but should be there later
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

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Re: Automatic advance unit
« Reply #6 on: 03.04. 2019 00:57 »

 Ok I dug out the spare ATD that came with a maggie that I picked up last year, and it seems as I suspected was brain-fart dreaming about that binding spigot idea...been a while since I had the nut and cover washer plate off, but as in the pic is obvious the bob-weight carrier is pressed on to the spigot, so........moving on to next great idea   *bright idea* *conf2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Spow11

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Re: Automatic advance unit
« Reply #7 on: 07.04. 2019 12:35 »
Morning gents, Thanks for all the replies. Here is an update.

I was kicking the engine this morning checking for a spark on the plugs. I left the timing cover off to check the position of the ATD. Before kicking the ATD was in the advanced position (weights out). After kicking the ATD went to retarded position (weights in). So I checked again and advanced the ATD by hand and it did not retard freely, but after kicking again the ATD was back in retarded position.

Cant quite figure out why this might be but I'm happy that all is working as it should be.

Steve 

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Re: Automatic advance unit
« Reply #8 on: 07.04. 2019 13:33 »
The points heel rubbing on the cam ring makes the armature too stiff to be moved by the springs.

That same drag makes the timing go back to the retarded position when the crankshaft is turning slowly.

Online metalflake11

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Re: Automatic advance unit
« Reply #9 on: 07.04. 2019 21:00 »
Hello Spow!......Please PM you address I can send the oil pump to, your money has landed, thanks!

All the best!
England N.W
1960 A10
England