"wasted spark"

[cdav59]

So after alot of research ive learned my bike is a "wasted spark" system........ so correct me if im wrong. In layman's terms it pretty much means that when the piston is on the exhaust stroke the second spark plug in the head fires for nothing? if this i so could i get away with running only the two spark plugs that actually do something. and if so how do i determine which plugs they are. im not very mechanically inclined and im learning as i go with this new build so forgive me if my questions seem ridiculous. its a 1985 honda shadow vt500c....

 

[onefourx]

So after alot of research ive learned my bike is a "wasted spark" system........ so correct me if im wrong. In layman's terms it pretty much means that when the piston is on the exhaust stroke the second spark plug in the head fires for nothing?

Thats how it works. Your bike uses 2 plugs per hole, and they both fire at the same time (compression stroke) and fire again on the exhaust stroke.
The wasted spark thing is so you dont have to run a "distributor" of sorts, you can just run signal right to the coil and the byproduct is to have 2 of the plugs sparking on the exhaust stroke.

 

[cdav59]

as of right now the bike runs off two dual tower coils to 4 plugs....... hypothetically speaking what if i went with 1 dual tower coil and connected it to 2 plugs (one in each cylinder).....would it affect the engine any

 

[mydlyfkryzis]

It may. 2 Plugs are used because lean mixtures don't ignite well, and 2 plugs give you 2X the chance for one to ignite, reducing the chance of a miss.

2 plugs are also used to start the flame front of the combustion in 2 spots, inducing swirl and better combustion, as well as shortening the total time the gases are expanding. Going to one plug may cause some misfires, as well as reducing power, as the timing and setup are for the combustion peak pressures happening at a specific time.

Many cars use 2 plugs per cylinder nowadays too.

What are you trying to accomplish, other then saving replacing 2 plugs?

 

[cdav59]

im trying to keep the wiring as simple as possible and i figure with one less coil things wouldnt get so hectic, and a little cheaper too

 

[VonYinzer]

im trying to keep the wiring as simple as possible and i figure with one less coil things wouldnt get so hectic, and a little cheaper too

Understandable thought... That said, you don't want to do it. The addition of the second plugs isn't really that big of a deal to wire, and allows the motor to functiont in its most efficient manor. You'll lose fuel economy as well as power across the reg range. Not to mention the timing issues that may be likely to occur.

 

[lurkmaster2000]

if your not too mechanically inclined why would you try to re-engineer the ignition system of your motorcycle yourself?
you should stick to what the factory gave you and worry about simple aesthetics and things that are easy to work with.

 

[cdav59]

im just trying to learn new ways to achieve the same result. this is my first build and im pretty much going in blind just trying to ask as many questions as possible

 

[cleoncleon]

I run a wasted spark ignition system for my 76' XS650 - Twin..
Kicks teh piss out of both the stock mechanical and TCI Ignitions released with the bike.
Pamco Wasted Spark designed by Pete McLean..

Better throttle Response.
Better Mileage.
Much better/Hotter Spark.
Aloot less wires, Alot less hassle.

He currently designing an Electric Advance unit to replace the Mechanical one, also..
I know he's made the system for Honda's aswell..

 

[cdav59]

Would that ignition work with a cdi ignition

 

[teazer]

No it would not. It is a points replacement system to upgrade an old points system to electronic triggering. Your bike uses a pair of pulsar coils to trigger the CDI and generate the sparks from a pair of dual tower coils.

Wasted spark means that it fires both cylinders at the same time and one of them fires the mixture and the other is "wasted" in as much as it doesn't do anything useful. That usually applies to 360 degree twins where both pistons are at TDC at the same time. Are you sure that yours is in fact wasted spark? If so, why do they fit two pulser coils? Usually one will do.

The simplest ignition for your bike is stock. If you know what you are doing it is possible to peel open the wring harness and remove circuits you don't need, but since most states actually require all the stock electrics, there's not a lot of point.

What exactly are you trying to achieve by getting rid of a system that works. Does your bike run at the moment or is it a basket case or not running?

From what I can see from your other posts, you appear to have chopped into the stock wiring without a wiring diagram or any wiring experience. The best system for that bike is the stock one using as much of the stock wiring as possible.