Should I be able to move the cam assembly easily about 10 degrees clockwise and anti clockwise against the auto advance mechanism and there be no evidence of springing back to relax the spring in the magneto end? I cannot start the engine without a backfire which suggests to me that the mechanism is always fully advanced.. However having checked the contact breaker gap being 16 thou and not 12 as the book say it should be; so maybe when I set it to 11 thou the narrower gap may compensate for any problem with the auto advance system. Advice appreciated please.
Its fairly normal for the…
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Auto Advance Mechanism
Hi Rodger and Robert
The Auto-Advance Unit is a strange beast.
Some years ago Les Emery [who worked at Lucas building magnetos, so should know!] told me it is not intended to spring back fully in your hand. Only comes to rest [at low rev's] when fitted.
Might be worth ensuring it moves freely; lube' with engine oil before fitting.
Have just tried some new springs on mine from RSS [Rex's Speed Shop] Tel: 01580 880 768. Very helpful.
or website. Excellent on my 650SS.
Hope this helps.
Tim
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Its fairly normal for the unit to be lazy in returning. My suspicion is that the backfire is caused by an intermittent spark at the plug. Plenty of culprits to check could be a poor lead or plug cap. well worth investing in a resistance meter , Should show no resistance.