Comet timing Advice

[alscomet]

I am just going to refit my K1F Magneto to my series C Comet with the points set at 0.012 In. Should I just have the points opening at 38 Deg BTDC with the auto spraged open, or do I need to set
it any differently now that ethanol is added to the Fuel by most suppliers.
Alan

 

[A_HRD]

Alan,

Opinions vary, but what passes for petrol these days seems to prefer 34 to 36 degrees max advance on my Comet. This assumes you have a fairly std set-up.

Peter B
Bristol, UK.

 

[b'knighted]

I agree that I would aim for 34 but do ensure that the full retard position is still before TDC.

 

[timetraveller]

All the above advice is good. Look very carefully at the stops on the ATD for serious wear. It is when these get worn (after 60 years of use!!) that the total movement from full advance to full retard is no longer what it was and then if you retard the fully advanced setting to about 34 you can get a fully retarded value of after TDC, WHICH IS NOT GOOD. If the stop look worn then it is possible to build them up with weld and then trim them with a file or grinder. Easier to do it before assembling everything and having the timing cover in situ.

 

[alscomet]

Thanks for reply time traveller,I doen't think I would like to weld up my stop lugs and then take a grinder to it especially as I only have a 9" Bosch to use.I set the points opening to 38 deg and then
took out the sprag and found the points opening at 3 degrees BTDC,Then set it to 36 degrees and again removed the sprag and found it was only at 1 deg BTDC, not wanting to start welding the stop lugs are quite soft so I slightly bent them both to give a stop at 2.5deg BTDC with the sprag removed
I will have to try it and see what its like,I can also get a bit more either way by opening or closing the points by a thou. thanks for all your input.What it really needs is an ATD with a 36 to 4 deg range. Alan

 

[bmetcalf]

Roy Price advertises new ATDs in MPH. Mine made a big difference and others recommend them also.

 

[alscomet]

Thanks Bruce for your input,when you read about setting the ATD it says set it to 38 degrees with the unit spraged and the points just opening and then that should give a reading of 4 degrees firing point with the sprag out at TDC.When
I am told to set it at 34 degrees on the forum if its a standard ATD without wear that would relate to 0 degrees at TDC unless the ATD is doctored or welded at this point,what are others doing? are they welding them up or fixing a shim somehow? My unit is a Roy price unit thats done less than 2K miles.Alan

 

[charlottevictoria]

Hi,
I am running my heavy Comet outfit (Blacknell Bullet) 1954 with 38 degrees an it runs more then 70 MPH, but I don't know weather the German fuel differs from the UK??? If I took less it would have been slower.
Best regards
Peter

 

[Martyn Goodwin]

So, what is the IDEAL setting to have to provide easy and reliable starting, that is the setting without any auto advance?

Ta Martyn

 

[charlottevictoria]

So, what is the IDEAL setting to have to provide easy and reliable starting, that is the setting without any auto advance?

Ta Martyn

With 38 degrees my Comet starts perfectly. Before the kick starter is down, the engine is running. After winter also the first (sometimes the second) kick lets the engine start. But the carb AND the magneto have to be good. Often the magneto becomes ill and there is no start when the engine is hot (so you have to push the bike). I guess the magneto becomes too hot under its cover??? (Caution: I use the highest German fuel; Piston 7,3:1).

Best regards
Peter