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Sam GiftTue Feb-01-05 12:14 AM

  
"Magneto Timing"


  

          

Gidday All......Have had to get the magneto on the Model 7 Dommie rewound and am seeking any advice on the easiest and most accurate way to set up the timing etc without all the gizmos and timing degree wheels, once the mag has been refitted to the bike. I know there will be someone out there who can help with a solution........many thanks
Sam

  

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RohanTue Feb-01-05 07:36 PM

  
#1. "RE: Magneto Timing"
In response to Reply # 0


  

          

Sam,
Lock the auto-advance mechanism with a wedge, and set the magneto so the points are just opening - while the piston is 1/4" down from TDC (top Dead Centre). A wire or thin rod down the plughole will give the 1/4" - make sure the rod is vertical, if a bit angled the measurement has to be a shade more than 1/4".

Make sure when you do up the centre nut on the advance unit that the timing doesn't move - this can be easier said than done with some units !!

have fun !!!

  

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RohanTue Feb-01-05 09:08 PM

  
#2. "RE: Magneto Timing"
In response to Reply # 1


  

          

The above was the easiest way.
The most accurate way is of course with a degree wheel and strobe timing light, the type that has an inductive pickup (clips onto the plug lead(s), runs off a 12v battery...).

hopethishelps...

  

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SamTue Feb-01-05 10:26 PM

  
#3. "RE: Magneto Timing"
In response to Reply # 2


  

          

Thanks Rohan, will give it a try this weekend.......Either side piston for TDC ????? or do I pick the right hand side piston when sitting on bike

sam

  

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RohanWed Feb-02-05 03:23 AM

  
#4. "RE: Magneto Timing"
In response to Reply # 3


  

          

Doesn't matter which side you do - but then always do the same side in future.

Make sure you set the timing on the compression stroke though, setting it for the exhaust stroke makes it hard (impossible) to start !!!

It doesn't hurt to then check the timing on the other side. Lots of maggies have been known to be a few degrees out side-to-side. If more than a degree or 2 different, Phil Irving, famous bike engineer, described how to "stone" (grind) a cam ring to get the timing even. If a long way out, a new cam ring can make the world of difference to a poorly running bike.

have fun...

  

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andersonWed Feb-02-05 01:49 PM

  
#5. "RE: Magneto Timing"
In response to Reply # 4


  

          

If the bike you have is a low tune 88 for riding at low speed and no hard use then you can go with the stick down the spark plug method. But if are using it hard you should really use a degree disc. Plus for hard use you absolutely must check the accuracy of timing on both cylinders.

The slip ring can be worn but also I have experience with the magnto bearings out of alignment and the shaft running out of parallel with the magneto body. This meant the timing was out by 10 deg plus one cylinder to the other. Check if you have the same points clearance on both cams of the slip ring.

and lastly if the bike is used hard I support Rohan when he says strobe both cylinders.

I melted two pistons before I learnt this.

(If you make a mistake and time on the wrong cylinder then just swap the plug leads over - I assume you are using a Lucas K2F mag.)

John

  

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triton thrashepSun Feb-06-05 02:28 PM

  
#6. "RE: Magneto Timing"
In response to Reply # 5


  

          

The slip ring is not the cam ring.
The slip ring is the bakelite (or similar) bobbin-shaped item with brass inserts for the HT pick-up brushes to rub against.

  

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andersonSun Feb-06-05 03:35 PM

  
#7. "RE: Magneto Timing"
In response to Reply # 6


  

          

Yes Sorry

Meant the cam ring. Senility setting in.

John

  

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Sam GiftMon Feb-07-05 09:23 PM

  
#8. "RE: Magneto Timing"
In response to Reply # 7


  

          

Hi again guys.......just a quick thankyou to all for the advice....gave it a try on the weekend and had no dramas, she fired first kick and ran smooth as. The bike is only used as a monthly social runner with the missus on the back so nothing too hard or stressful from a race perspective....Thnaks for all the help, now if only I can find an original Model 7 front mudgaurd or a very good copy

thanks again

talk soon

Sam

  

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