Magneto drive chain

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Tazmantic
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Posts: 388
Joined: Tue May 25, 2021 10:50 pm
Location: Oxfordshire UK

Magneto drive chain

Post by Tazmantic »

Would this be too loose for the mag drive chain??

If so do I have to pack the mag upon shims to tighten the chain :x
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Andy51
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Joined: Thu Mar 31, 2005 1:00 am
Location: BERKS UK

Re: Magneto drive chain

Post by Andy51 »

The mag mount is hinged - loosen front stud nuts slightly, then loosen rear stud nuts. Lever up rear of mag mount with screwdriver or similar until mag chain has 1/4 in play, then tighten rear stud and check play again. Finally, tighten all nuts on both studs. Andy
Tazmantic
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Posts: 388
Joined: Tue May 25, 2021 10:50 pm
Location: Oxfordshire UK

Re: Magneto drive chain

Post by Tazmantic »

Cheers Andy I literally just found that, that’s me asking before I look 🤦???
Everyday’s a learning curve.
56G80S
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Posts: 3354
Joined: Wed Oct 12, 2005 10:45 pm
Location: N YORKS UK

Re: Magneto drive chain

Post by 56G80S »

I'm an idiot - this looks like a manual spark machine! Didn't look close enough. The advice still holds good for others though.

Andy51 is spot on. Don't forget to find any tight spot and set it there. I recall guru Alan Jacobs (Biscuit) stating that more problems are caused by a chain a bit too tight than one with the chain a bit too slack.

Certainly, a tight mag chain can cause problems with the auto advance & retard (ATD) sticking as I know from experience.

Also, be sure that the back of the ATD doesn't foul the chaincase. If the large "doughnut" between the mag and the case is too wide it will push the case onto the back of the ATD. Firstly, the slots in the mag mounting can be used to adjust the amount of entry into the chaincase to ensure that the chain run itself is straight, camwheel to ATD sprockets. Then check the doughnut is a sliding not force fit. I've cut it and refitted it once the right doughnut width obtained with gentle use of a tie wrap so there's no need to pop things apart.

Johnny B
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