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Need Help! Changing dual Lightspeed Plasma II to Slick Mags

Ben R

Ben R

Well Known Member
I am in need of some advice guys.
A friend of mine decided to replace the dual Lightspeed Plasma II ignition system on his RV-8 with two standard Slick mags. We spoke with Joe at Champion/Slick support, who recommended two 4371 Slicks with dual impluse couplings based on the engine/prop combo on the plane (IO-360 A1B6 with a lightweight composite C/S prop). The dual Lightspeed system that was installed required a small battery as a backup power source in the event the aircraft battery/electrical system failed. The entire Lightspeed system was removed, Slicks installed, new P-leads fabricated and wired to the ignition switch, new plugs installed, and the mags were timed.
For some reason, the plane refuses to start. We have removed and re-pinned the mags per the Slick procedure (twice), verified timing (three times) with a timing tool, and verified spark at each plug at the appropriate time in the rotation. We have even disconnected the P-leads and attempted to start with no success. The engine will fire (only run a second or two) but only when the mixture is full lean. Any attempt to richen the mixture will cease all firing. The engine normally starts easily with no issues. We have tried starting multiple times with hours between start attempts (to eliminate the possibility of flooding during prolonged starts). There were no changes made to the fuel system or injectors. Is it possible that the Lightspeed system requires a different fuel adjustment that a standard Slick mag does not?
We are all scratching our heads. The owner is an A&P and replaced the mags on my RV-6 last year in no time and with no issues.
I plan on calling Joe again tomorrow but I'd appreciate any advice...especially if someone has made a similar swap.
Thanks in advance!!
Ben
 
Ben R said:
verified spark at each plug at the appropriate time in the rotation.
Ben
Click to expand...

We you sure they were firing on the compression stroke and not the exhaust stroke? You can confirm either by removing the valve cover. At TDC on compression stroke, you should be able to slightly compress both rockers on the pushrod side. On the exhaust stroke, one or both will be un-compressable. You can also stick your thumb or finger in the sparkplug hole, blocking the air. On the way from BDC (180* from TDC on flywheel) to TDC, compressed air will force your finger out of the hole on the compression stroke and you will feel nothing on the exhaust stroke.

EDIT: sorry, read the second half of your post too quickly. Seems you get initial firing, but then dies after 1-2 seconds. Certainly sounds fuel related. How much are you priming it? If it is kicking over in an ICO position, it had to have gotten fuel before you cranked it. You may just need to re-learn your starting technique. Any EI will fire a wider range of mixtures than a mag will. It will be a bit harder to nail the sweet spot with the mag. It will not be as easy to start as easy as it used to. Do some searches on FI starting techniques. I just converted to FI and am still learning. I still haven't figured it out yet. Lots of cranking as I learn.

Larry
 
Last edited:
Compression stroke verified.

Thanks Larry. We did verify that we were on the compression stroke by placing our thumb over the plug hole.
 
After removing your Lightspeed, did you plug the open manifold pressure line?
On a dual Lightspeed you would have 2 disconnected manifold pressure lines.
 
Are you sure that the impulse couplings had "snapped" before timing?
If not ignition timing would be way off.
 
plugs?

The new plugs are aviation plugs with a .018" or so gap, not auto plugs with a huge gap, right?
As Mel asked, are you seeing plugs fire close to TDC (since both mags have an impulse coupling)?
 
We did make sure the impluses had snapped before timing and they are firing right at TDC. The plugs are new aviation plugs...all auto plugs removed.
 
Are you using a key switch or push buttons and toggles.? If your using a key switch, make sure it's wired correctly.
 
The fact that you disconnected the P-leads takes the switch wiring out of the equation. With you verifying a spark at the correct timing, and you are sure of that, then chances are you have a fuel problem. You may not necessarily have 2 open manifold pressure ports, as common practice is to Tee them, but do check. Air/Fuel/Spark, right? Do check the fuel system and make sure you are getting fuel.

Vic
 
Ben R said:
We did make sure the impluses had snapped before timing and they are firing right at TDC. The plugs are new aviation plugs...all auto plugs removed.
Click to expand...

If the impulse coupling has popped, shouldn't the timing be at 25 degrees before TDC? I thought it was only TDC before the coupling had popped. In other words, the impulse coupling should snap at TDC.
 
The impulse should snap at TDC or sometimes a little after, depending upon the lag setting of the mag.

Timing of the mag to the engine has to be done AFTER the impulse snaps. Then you turn the prop backwards to just a little before the timing mark you want, and then come up on the mark stamped on your engine for timing and set the mag so the points open (the box buzzes or lights up), typically 20-25 degrees for our engines.

If you don't let the impulse snap you will get an erroneous timing value.

Vic
 
Here's the technique we are using:
1. Pin the mags partially in the "L" hole and gently rotate backwards until the pin bottoms out (backwards due to the impulse coupling).
2.Confirm that the #1 cylinder is at TDC by the location of the piston (by feel) on the compression stroke which also corresponds with the TDC mark on the flywheel.
3.Rotate the prop back 20 degrees based on the timing mark on the flywheel (engine is 20 degree lag).
4.Insert the mags, snug, remove timing pins
5. Advance the prop past the impulse snap.
6. Turn prop backwards slightly past desired timing mark.
7. Advance the prop to the 20 degree mark on the flywheel and confirm that the timing lights illuminate on the synchronizer and adjust as necessary by moving the magneto slightly.

Am I missing anything?
If not, next step is to check internal mag timing per Vic's recommendation.
 
Timing

The 180 hp engine should be timed to 25 degrees. Establish compression stroke on #1 cylinder. Back the prop up to slightly past 25 mark. Normal direction of rotation to 25 degree mark.
Turn the mag in the normal direction of rotation past proper timing hole until impulse snaps. Back up to timing hole. Insert pin and install mag with nuts just snug enough to allow rotation. Fine tune with buzz box.
You seem to be confusing timing mark and impulse lag angle among other things.
Once compression stroke is established on #1 you only need to be concerned with TDC if you are using a protractor style device on the spinner. NOT if you are using timing marks on ring gear support.
 
Timing

To clarify this further based on your last post you likely have the mag timed somewhere around TDC. Properly timed the impulse will fire the first cylinder around 5 degrees before TDC but the impulse will then disengage and the next cylinder will fire at 25 degrees before TDC.
DON'T confuse the lag angle with the normal timing.
 
SOLVED!

Just a follow up...the problem was the E-gap setting in the mags (the mags were used). Timed them correctly internally and it's running great now. Thanks to Vic for his advice and to all who responded to the post!
 
I know this is a little bit of thread drift but, can I ask why you (and a couple of others) have taken the Plasma II off and put mags on. I have plasma II's fitted to my 7 ?
 
Starting

I would remove the four top plugs, connect the wires and hand prop with ign. in on position. Spark should be nice clear blue color. The only thing changed was the mags and they are new but if you used resistor plugs and resistor wires there will be too much resistance and a very weak spark, hence very easy to flood. Regards, Carroll
 
PIN 37 said:
I know this is a little bit of thread drift but, can I ask why you (and a couple of others) have taken the Plasma II off and put mags on. I have plasma II's fitted to my 7 ?
Click to expand...

Phil,
My friends -8 came with two Plasma IIs when he purchased it. This required a separate, small battery to use as a backup source of power in the event of an electrical failure. He decided he would rather go back with two standard mags (eliminating the backup battery) and use a simpler system that he was more familiar and comfortable with. I made the same switch on my -6 last fall from LASAR to Slicks and have been more than happy with the change. I'll be posting his Plasma IIs soon. They were working fine when removed.
Ben
 
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