Ignition Timing

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Duncan
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Re: Ignition Timing

Post by Duncan »

You are aware that the disc will then turn at half engine speed?
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spookefoote1956
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Re: Ignition Timing

Post by spookefoote1956 »

Is that exactly half and will that affect the 39 degrees?
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Duncan
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Re: Ignition Timing

Post by Duncan »

Generally a degree disc is unnecessary, if the timing is roughly where it should be by sticking something down the plug hole, try your normal starting technique a couple of times, then give it a big hand full of throttle and try again.
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Duncan
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Re: Ignition Timing

Post by Duncan »

Yes exactly half
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spookefoote1956
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Re: Ignition Timing

Post by spookefoote1956 »

Thanks for your thoughts Duncan. If I were to try my method would I be looking for 19.5 degrees? Sorry my brain is currently in mush mode.
Hail Joe Lucas ............ Prince of Darkness!
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spookefoote1956
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Re: Ignition Timing

Post by spookefoote1956 »

I notice that young Spriddler has suggested in other posts 7/16" btdc due to modern fuels. How do you feel about this?
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Duncan
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Re: Ignition Timing

Post by Duncan »

Sounds about right, but your margin for error will also be doubled (1 degree out will equal 2 and so on), most find tapping the cam sprocket the most effective way of setting the timing as it avoids damaging the mag with an over enthusiastic "tap", you may struggle to do this with a timing disc on it.
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spookefoote1956
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Re: Ignition Timing

Post by spookefoote1956 »

I was going to connect the disc to the lower cam sprocket. I see what you mean about the margin for error. Stick down the plug 'ole it is then.

Edit: Scrap the above, I realise what you mean now tapping with a knocking stick as opposed to tapping a thread!
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
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Duncan
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Re: Ignition Timing

Post by Duncan »

To be honest I have never had to reset the timing on my coil ignition 350 in over 25,000 miles it still is as the previous owner set it (have had to change the points though). My 37 250 is set to the book (with a piece of wire in the plug hole) and is a lot more sensitive to the A/R position when riding.
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spookefoote1956
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Re: Ignition Timing

Post by spookefoote1956 »

Thanks Duncan, your help and advice is much appreciated.
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
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