80 gs450: convert to points?

[pete]

Still no word from Mr. Riggs.

But, I can kind of sum up what he did on the xs650 HEI system...

He modified a pickup and reluctor from a toyota distributor to send a signal to the HEI module which then fired a chevy dual output coil. Massive sparks can be made with chevy coils!

On my xs650 I went from two single output coils to one dual output coil... it just fired both cylinders at the same time since the pistons move up and down at the same time. How is a gs450 phased? Vibrations aren't nearly as bad as my xs650, so I'm guessing both pistons do not go up at the same time?

Aaaah I see. Was the XS650 points though? What I'm trying to achieve with the HEI modules is to avoid changing anything from stock and use the OEM pickup coils.

The 450 is a 180 degree crank, and if you look behind your timing cover on the right you'll see the two pickup coils are opposite each other and that the magnet is only embedded into one side of the governor.

[SqDancerLynn1]

Points advance and igniter advance units are different!!

[pete]

Points advance and igniter advance units are different!!

They certainly are! Fortunately both of ours are mechanical advance units, so no dramas there and it's the only reason the HEI modules have a chance of working

[mlc216]

So wouldn't a single pickup with a dual pole reluctor do the same thing as two pickups at 180 deg with a one pole reluctor?

I guess my biggest question is why do you have to wire in the circuit of resistors, etc. with two separate HEI modules when the xs650 setup can run off one HEI module and a dual output coil?

[mlc216]

Also, pete the xs650 setup used a points plate without the points to mount the pickup and then the reluctor was modified to fit on the advance shaft. The setup is orignally used on a four cylinder car, so two of the poles on the reluctor were ground off leaving two at 180 degrees.

[mlc216]

Ok I have another question... In the 4 stroke cycle there is an intake stroke (down), compression stroke (up), power stroke (down), and exhaust stroke (up)...

On a 180 deg crank:
If you look at one cylinder, it only needs the sparkplug to fire at the top of the compression stroke... as this fire happens and sends cylinder 1 into the power stroke, then cylinder two is coming up in its compression stroke. This creates a syncopated rythym instead of a steady beat. In other words it only needs to fire 2 of every 4 cycles... so does it actually fire every cycle and just have no effect when it fires at the top of the exhaust stroke? Or does the igniter take the signal and tell the coils only to fire every other signal for each cylinder?

[cowboyup3371]

From what I understand, yes. Something about a wasted spark.

[mlc216]

So it does fire every time and there is a wasted spark?

[mlc216]

Ok so this is the simple xs650 setup...

[mlc216]

And this is what I was thinking...

[pete]

Ok... Cowboy has it, it's a wasted spark setup.

On a car, distributors don't run at crank speed, so are able to spark only when required.

As bikes generally are timed directly off the crank, they generally have a wasted spark setup.

This is a very simplified explanation but best I can do, I ain't a guru.

As to one or two circuits, the 180 degree firing order requires two separate circuits to function.

If you used one module, it would fire both cylinders simultaneously, meaning one cylinder would be firing 180 degrees out and you'd only end up running on one cylinder.

I suspect that would also result in other far more destructive results too, although not sure exactly what they would be.

[mlc216]

I still don't understand how a system with two pickups and one pole fires any different than a system with one pickup and two poles.

[pete]

Actually I just looked at your diagram again...

The way you have the second diagram will have both plugs firing at the same time.

The problem with this is that when the left cylinder is at the bottom of its stroke and the right cylinder is at the top of its stroke (180 degree crank remember), the spark will fire on both cylinders, which is 180 degrees out of time for the left cylinder. It needs to spark only at the top of its stroke.

Does that help at all?

I'm not very good at explaining this, although it does make sense in my head...

[mlc216]

Yeah I don't know why it is so hard for me to understand. I guess with two pickups and one pole it fires two different signals so even though it has a wasted spark, the plug always fires at the top of the stroke. Got it. I think haha.

[pete]

Yup you got it! Sorry my explanation was such crap... oh well... haha