Dual vs. single point distributor

[oldman]

Got a manual advance dual point distributor for my '52 pan. Can you hook the leads together and run with a standard single points coil? Building a pan chopper.

Thanks

[Cotten]

Oldman!
I don't think so. I think the points cam profile won't allow it, I think. Or atleast I can't think of a way to make it work.
Personally, I think the dual points setup was the best the Factory ever put out. It makes it worth cramming a second coil on it somehow. But timing is a bitch without a degree wheel to mark your flywheel.

[oldman]

I believe both cylinders fire simultaneously, although only the one on the compression stroke at the time makes use of the spark with single points. With the dual point breakers each cylinder is timed to fire independently on compression so two coils are required right? The question is who makes a stock coil or rather coils for 1960 to 1964 panheads and how are they mounted on the bike?

Ed

[Olddad]

What's the advantage to having dual points? My '59 has a single point system, and the same points that were in the bike when I got it in 1972. The bike starts about as well in the winter as summer (which is saying something in Minnesota!). I am using 20W50 oil, and when I have run it in mid-winter, below zero, I have used 10W40 both in the engine and transmission. I really do not put a lot of miles on, but I do have a sidecar attached and so the engine does get a workout. The only starting problem I haven't figured out is how to start the bike when it is luke warm. My latest theory is that at that point I have a dry carburetor then. Otherwise, hot or cold it pretty much starts right off. By the way, I still have the 6 volt system too. -- The Ol Dad

[VintageTwin]

My single-point '59 runs with the Linkert just a tiny bit on the rich side, and it suits my motor fine. If I start my machine and it's warm to hot, I always kick the motor through once with the key off, then retard the spark at least mid-way, then put the pedal on a compression stroke at about 8 o'clock, and with my left foot firmly planted on the ground, turn the key on, and I give the motor one kick (which with the pedal way on down there, there is only enough leverage and swing, to turn the flywheel over once) and one kick is all it needs to fire. I never jump up and down on the kick-starter from the left side. (Had the kick-starter dis-engage on me once doing a "left side kick", seperated my knee that time..limped for a couple weeks). The kick-thru should appear effortless, and it will, as long as your left foot is on the pavement. You couldn't do this with a long stroke Sportster or even a Shovel....only works on a Pan or Knuckle. The ultimate rider and crowd pleaser, is when I can start the (warm-hot) motor right into a steady idle. No rev of the motor at all...just kick it from dead... into a steady idle. Then without looking around for applause (called "claiming" in surfing)...balance the machine with my feet on the footboards, shift forward into first, and baby the clutch pedal, where it makes the motor slow-idle and smoothly lope away....slowly. Rocker clutches are great for that.

[Cotten]

OldDad!
The advantage of the dual point circuit breaker is that is is a single-fire system: each cylinder is timed individually, and therefore more accurately.
I am also told that it reduces certain vibrations, eliminates broken top motor mounts, and a whole lot of other miraculous things, but just the smoothness and even burn between cylinders is enough for me to appreciate it.
And with a dual exhaust it sounds really tits.

[Olddad]

With my '59, if I stop for gas, or it's just shut off for 1/2 hour or so, it starts most always with just one kick. No kick through with the ignition off or anything. And when it's really cold, say it's sat a week and it's 30 degrees out, then it's 3 kicks with the choke full on; then with the throttle 1/3 on, and the choke 1/3 on, it usually starts with the 1st kick. I always retard the spark. But say I ride somewhere and then let the bike set for 2 to 3 hours. Then I have a problem starting. I'm thinking that the carburetor is dry. I always shut off the gas, and maybe the hot engine cooks the float bowl dry, or maybe it leaks out. I'm going to try turning on the gas well in advance to starting. Maybe the bowl will fill up. On my old Zuendapp there's a tickler under the carb. You hold it till your finger is wet with gas, then you start. At that point the float bowl is full. So that's my current theory. As far as idling and smoothness I don't see many Harleys, newer or older, which run smoother. It's fun sometimes to throttle way back, with the spark retarded, and just tick along at about zero mph (as long as you're in no one's way). With the sidecar on I can walk along side (in low gear) if I'm in a park or somewhere where there is no traffic problem. So I don't see how a 2 point system could be better. --The Ol Dad

[VintageTwin]

Kick it through once with a full choke when it's a hot re-start. The factory book says that. But since mine runs rich, a dry kick through is what works for me. Any mis-firing and smoke coming back through the carb? Mine does that when it's hot occasionally...but I always make a big deal out of it and wave my hand through the smoke like I'm putting out a fire. Cheap theatrics.. but then again...don't look around to see who's watching...you'd want it to appear like your just... regular people... starting his machine. This is all controlled-chaos after all.

[Ente]

Hi.. newbie nere.. Swedish guy, run a 55-pan in 49-frame. I was thinking to do the same thing with the leads... but after a little more thinking and a couple of beer I figured out that... Since you have 2 points, and they opens on different time.. ONE is always closed.. so you will always get the coil connected with common through either the rear or the front point.. MAYBE you can solve it with 1 diod on each lead to block the backway-earthing...

[dirtpandan58]

Doesn't a dual point system use two coils?

[VintageTwin]

I see a V-Tech® Single Fire Coil here in V-Twins March Monthly (VT 32-0467), says it gives 1 spark for each cylinder as fired and will mount to stock bracket and accept stock coil cover. 4.3 ohms.

[kell]

Ente:
You don't necessarily always have a set of points closed, it depends on the dwell. Dwell has to be less than 315 degrees to avoid the problem. Dunno what the dwell is on the dual-point distributor, but would hazard a guess it's not quite that long.

[Ente]

Kell:
You sure have a point.... or two

Since my dual-point distributor still is loose...
I just have to measure it...
not the degree or dwell, but if I really get 2 physical on-off during a round with the 2 leads connected to each other..and not just a loooooong forever ON(=common).
The issue is'nt really a big deal... but interesting..
I will be back after the weekend.....with da anzwer
everybody out there is waiting for...

[kell]

Methinks it's worth having separate coils, even if it means fabbing a coil bracket. I did that anyway for my double plug STD heads. I can also go single-fire now if I want to.
I have in mind a home-brew single fire electronic conversion of my old single point breaker using hall effect sensors. Have ordered the hall effect chips and will get IGBT's (insulated gate bipolar transistors) to drive the coils. I intend to use a steel shutter disc between the magnets and hall effect chips. I'm aware that shutter wheels go with optos and hall effects don't generally use them, but I think this is the way to go. I can mount the hall effect chips as far out as I need, a good inch from the center of rotation, so I'll be able to get them precisely 315 degrees apart (this will fix the relative timing of the cylinders, so you only need the one flywheel timing mark). That way too I can easily make the dwell however long I want it.
Which brings up the question of how much dwell do you need on a pan?

[Ente]

Oldman:
Let's go back to your original-question for a moment..

NO... you cant connect the two leads from the two points if you want to use a single coil... If the distributors cam only have one lobe, and it open one set of points, the other set of points is closed and vice versa... the connected wires always will be connected to common through either of the point-sets and no on-off-pulse will occur to the coils primary-side....
If you want to go single... (in distributor terms)
change the distributor-cam to the one with two lobes and remove one set of points.... Or find a nice bracket that fits two coils and go dual.....