Technical Distributor weights

[BarryH]

Hi all, have been tweaking timing over the last couple of weekends on the 500F. Carburettor mixture is showing a nice bunsen blue now at idle. The idle speed seems to be at its happiest around 1000-1100 rpm and the timing at this speed is slightly advanced of 10 deg as per video where I am thinking unleaded fuel may be a factor here with a slower burn. The question is that if I rev the engine the timing doesnt instantly return to the prior timing position immediately. I am running a powerspark module instead of points but I noticed that there was no felt pad on the distributor shaft so thinking that no oil to lubricate the weights which may be sticking. Any thoughts much appreciated. Barry

 

[bugsymike]

Hi all, have been tweaking timing over the last couple of weekends on the 500F. Carburettor mixture is showing a nice bunsen blue now at idle. The idle speed seems to be at its happiest around 1000-1100 rpm and the timing at this speed is slightly advanced of 10 deg as per video where I am thinking unleaded fuel may be a factor here with a slower burn. The question is that if I rev the engine the timing doesnt instantly return to the prior timing position immediately. I am running a powerspark module instead of points but I noticed that there was no felt pad on the distributor shaft so thinking that no oil to lubricate the weights which may be sticking. Any thoughts much appreciated. Barry

Sounds logical to me.
In the old days when points were common, on every service I used to oil the distributor shaft, then work the shaft using the rotor arm to check the balance weights were moving and the shaft hadn't seized.
I also used to oil down towards the balance shafts where possible via any holes in the base plate.
You could usually feel the return springs a little working. I would use engine oil via a squirt can.
Where applicable I would test the vacuum advance side too.
Some electronic ignition systems work from a fixed timing point and have built in advance capabilities, but probably not in your case.
Another point 1000-1100rpm idle sounds high to me so may stop balance weights returning to normal static position, weak balance springs could also be a cause, although note if you examine balance weights and springs there is usually two and one may appear loose compared with the other , but often that is a feature of the advance set up so do not try and shorten it etc.

 

[the hobbler]

Sounds logical to me.
In the old days when points were common, on every service I used to oil the distributor shaft, then work the shaft using the rotor arm to check the balance weights were moving and the shaft hadn't seized.
I also used to oil down towards the balance shafts where possible via any holes in the base plate.
You could usually feel the return springs a little working. I would use engine oil via a squirt can.
Where applicable I would test the vacuum advance side too.
Some electronic ignition systems work from a fixed timing point and have built in advance capabilities, but probably not in your case.
Another point 1000-1100rpm idle sounds high to me so may stop balance weights returning to normal static position, weak balance springs could also be a cause, although note if you examine balance weights and springs there is usually two and one may appear loose compared with the other , but often that is a feature of the advance set up so do not try and shorten it etc.

As"Bugsy" commented---1,000 to 1,100 rpm is too high an idle, it should be about 900 rpm, and at those revs, the ignition light will be flickering (that is if you have a dynamo). Your slightly hire idle-speed may indeed be slightly activating the advance bob-weights. New bob-weights and springs are available from one of the continental suppliers (but off-hand, I can't remember who).

 

[Flo500]

Hi all, have been tweaking timing over the last couple of weekends on the 500F. Carburettor mixture is showing a nice bunsen blue now at idle. The idle speed seems to be at its happiest around 1000-1100 rpm and the timing at this speed is slightly advanced of 10 deg as per video where I am thinking unleaded fuel may be a factor here with a slower burn. The question is that if I rev the engine the timing doesnt instantly return to the prior timing position immediately. I am running a powerspark module instead of points but I noticed that there was no felt pad on the distributor shaft so thinking that no oil to lubricate the weights which may be sticking. Any thoughts much appreciated. Barry

Hi Barry,
Random question, what your procedure for mixture setting? Curious how you observe the bunsen blue flame?

 

[BarryH]

Hi Barry,
Random question, what your procedure for mixture setting? Curious how you observe the bunsen blue flame?

As"Bugsy" commented---1,000 to 1,100 rpm is too high an idle, it should be about 900 rpm, and at those revs, the ignition light will be flickering (that is if you have a dynamo). Your slightly hire idle-speed may indeed be slightly activating the advance bob-weights. New bob-weights and springs are available from one of the continental suppliers (but off-hand, I can't remember who).

Many thanks guys, I will take a look at the Distributor internals and dial back the idle speed a little and yes a dynamo

 

[BarryH]

Hi Barry,
Random question, what your procedure for mixture setting? Curious how you observe the bunsen blue flame?

Hi with regards the bunsen blue, I followed the helpful comments on many of the posts to turn out the mixture screw 1 -1/2 turns from fully wound in to get me in the ballpark adjusting the idle screw a little as I went and then used a Gunsons Colortune to fine tune. Still some tinkering to go, it feels like spinning plates atm timing >> mixture >> idle, I am new to air cooled engines so every days a school day