Brian 54G80S wrote: ↑Mon Jan 15, 2024 11:15 am
Can I access the auto advance mechanism to clean and lubricate without removing the magneto?
I haven't had or worked on an auto A/R mag (a bit too 'modern' for me) but if you have a read of these Lucas manuals they should be of some help........
Yes. So the big question is do you have the autoadvance unit? Does your timing side case have a bulge? That's where the unit sits. If the timing case is flat you have no advance. Assuming it does have the bulge then remove the timing cover. I would start by checking the chain tension and if it is tight set it to have some slack but so that the chain cannot hit the side when flexed hard.
Next open the bob weights manually and see if they will snap back. As you say try a small amount of oil.
The final check is messy run the engine and blip the throttle. If working correctly you should see the weights move outwards. Warning this will probably spray the oil and grease everywhere.
These units are prone to failure due to wear on the pin that the weights rotate round. With a lathe and competent engineering they can be replaced. Your problem is unlikely to be the springs as these do fail but would making it advance too soon and so harder to start rather than not running at higher throttle.
If the auto advance is missing this explains your problem, timing is fixed and set to help starting, you will never get full power.
clive wrote: ↑Mon Jan 15, 2024 8:09 pm
Yes. So the big question is do you have the autoadvance unit?
That had also ocurred to me Clive, as mags for stationary engines didn't have auto A/R and since the bike had been unused for 25 years many things could have been changed. Maybe the previous owner laid it up because he had the same problem as Brian.
'There is a tide in the affairs of men
Which taken at the flood............'
I note the instructions regarding controls seem to suggest that the "Air Lever" should be pulled inwards in normal operation and pushed away for starting.
Thats very different to how a choke usually operates, usually you pull them out to choke the airlow/increase fuel mixture for starting.
Am I missing something?
Brian 54G80S wrote: ↑Tue Jan 16, 2024 8:32 pm
I note the instructions regarding controls seem to suggest that the "Air Lever" should be pulled inwards in normal operation and pushed away for starting.
Exactly that. I suggested checking it because it's a common misconception by those of us more familiar with car choke controls.
If you open the throttle wide and look or feel into the carb intake when the choke is Off (cable pulled tight - engine not being choked) there will be no obstruction except the needle. When the choke is On, cable slack (i.e. for starting) there will be the brass choke slide in the airway.
P.S. Since it's mid summer at the mo in Queensland (circa 30 degs?) I doubt that you'll need the choke for starting - just tickle the carb and she should start and run O.K.
'There is a tide in the affairs of men
Which taken at the flood............'
How I wish it was only 30 degrees! Worst summer we have had in a long time. Many 35+ days, frequent heavy rain which results in humidity which is very challenging.
Thanks for your help and advice as always. I'm going to check auto advance and try again this coming weekend.
PS, I'm going to be in the UK in July this year and I'm going to the club shop for a look.
I was plagued with these kind of problems and the AR unit is a good place to look. There is a trick to getting it off the shaft which I know how to do when at the job but memory fails when it's not in front of me, someone else will help. You'll be astounded at how much filth comes out if you use Rob Harknett's approach of vigorous working it in white spirit. It should snap back fine when off the shaft, won't necessarily do so on the shaft as there are resistance factors in play.
Also second the comment about overtightened chain being a problem. I recall Biscuit's comment that a very slightly slack chain is better than one that's too tight. Also useful to check chain alignment as you don't know the history and as it's not the "correct" mag someone may not have used the facility to move the mag across the frame. Also, while the AR is off, look for any witness marks that the rear of the AR isn't fouling the alloy chaincase; mine was!
Hi, you can remove and clean the Lucas ATD easily without removing mag, but of course you will have to re-time the ignition. They often seize up because the is no provision to lubricate central spindle in situ - mine did. There are several websites out there telling you how to strip and clean ATDs. Andy
