OK boys and girls. I just bought a used motor and it has been dual plugged. Anyone know if the ignition has to be retarded, or what the advantages or disadvantages of this modification are.
It should burn the fuel more completly and overall should run a little better, but one disadvantage would likely be more heat, but you could throw some more fuel at it to help cool the engine. Post up some pics of it, I want to see where they put the other plug.
Use colder plugs (NGK 5329 ... they used to be called DPR9EA-9) to cool it down a little; or just add some ethanol :) . Dual plugs with staggered timing sounds perfect for burning ethanol (along with domed pistons and shaved head).
I was talking to my machinist about this when he was boring some cylinders for me. It came up since he was relocating a plug in a vintage race bike. If it is where I think it is, vertical next to the valve cover, this will provide a more even and complete burn of the fuel. I would run another pair of coils (or dual plug coils) so they fire at the same time and leave the timing the same.
Quote from: sprint_9It should burn the fuel more completly and overall should run a little better, but one disadvantage would likely be more heat, but you could throw some more fuel at it to help cool the engine. Post up some pics of it, I want to see where they put the other plug.
I will post a picture of it mid week. I am off to a wedding in a few minutes.
Quote from: dgyverI was talking to my machinist about this when he was boring some cylinders for me. It came up since he was relocating a plug in a vintage race bike. If it is where I think it is, vertical next to the valve cover, this will provide a more even and complete burn of the fuel. I would run another pair of coils (or dual plug coils) so they fire at the same time and leave the timing the same.
Yes, the second plug is vertical. I am surprised it fits between the valves.
I will be taking the top end of the motor apart before I run it. I wonder what other goodies I will find.
Quote from: D-DayOK boys and girls. I just bought a used motor and it has been dual plugged. Anyone know if the ignition has to be retarded, or what the advantages or disadvantages of this modification are.
As I recall, one of the advantages of a dual plug set-up is that you can advance the timing more without detonation.
Quote from: D-DayI will be taking the top end of the motor apart before I run it. I wonder what other goodies I will find.
Curious what size pistons are in there, and what profile. High lift cams too?
I know this doesn't help any, but my dad just picked up a '72 CZ380 motocrosser, and it's got dual plugs. Slightly different purpose though... :lol:
and what is that slightly different purpose......
2 stroke singles with a spare fouled plug.....
:? :? :? :? :?
Indeed!
A popular mod before the digital ignition times was to run 2 coils and fire both at the same time, for all purposes listed above for the 4-strokes, but the new ignitions light hotter, faster and are obviously more reliable.
Don't even need to go to a reed valve anymore with the quality of mixer oils out there today to prevent load-up. It actually idles like a modern MX'er, and that's pretty darn impressive in my book.