Horn cuts out Engine with Lukas CDI

[Paul_from_Thornbury]

Had LT coil failure. Ordered and fitted a Lukas CDI. Tried with a standard regulator and a BGM regulator I'd ordered.
Reedspeed diagram is wrong, it shows connecting Lukas on same side as input from Stator, don't get a spark like that.
When connected correctly, with a Lukas on output of regulator it starts.

However I find that operating the horn cuts out the engine.
Tried with both regulators, same response.

So the horn drags too much power and cuts signal to the Lukas cutting the engine.

Is this correct, should I be going DC with horn? The BGM regulator gives me a DC supply.

[Fast n Furious]

Horns consume high peak current.
I suspect the BGM regulator o/p may not be powerful enough to provide what is necessary.

[Adam_Winstone]

Does it do this with the lights OFF?

[HxPaul]

I've been using the Lukas CDI for quite some time,I just followed the wiring diagram that came with the CDI and it works perfectly.I have the yellow wire from the stator going to the regulator and from there to the CDI,both fitted onto one spade connector.

[Paul_from_Thornbury]

Haven't solved horn problem, engine cuts out with lights on or off. Measured voltage at Regulator, around 11v, as soon as horn pressed its drawn down to nothing and engine cuts.
Took for a good run today, very nice at lower revs, much cleaner running. However it won't rev out beyond 7k, used to get 8k+ with an LT coil and CDI and coughs/splutters/misfires at those high revs with Lukas.
Disconnected the wiring harness so it's just Stator and cdi connected to check the rest of wiring not causing a problem but still the same.

[HxPaul]

Are you using this CDI https://www.ebay.co.uk/itm/Readspeed-Ze ... 0005.m1851 Or the AC one that runs off your lighting coils.

[Paul_from_Thornbury]

I'm using the Lukas, but I'm not sure it's AC only. I've got a BGM regulator which has a DC supply. To get around the issue of the AC horn dragging down the Lukas I thought about using the DC supply to a battery and using this for the Lukas isolating the Lukas from the rest of the scooter.
With the Lukas running off the battery. It's now going to around 8000 rpm, where it's starts to hesitate and misfire. It would previously run to around these speeds but wouldn't misfire with an LT coil and CDI.
Scooter is now AC for lights and Horn, with AC supply to an Intelliconverter to run the SIP and the DC output of the Regulator charging a battery that only supplies the Lukas.
Will speak with Readspeed on Tuesday.

[HxPaul]

I'm using a standard Indian 12v system with this kind of regulator https://www.ebay.co.uk/itm/LAMBRETTA-GP ... Sw5cNYK02n

[Fast n Furious]

Paul.
Is your HT lead copper?
Is your plug cap resistive or straight through?
Is your plug resistive or not?

[MickYork]

Fit a battery.........

[HxPaul]

[quote="Fast n Furious"]Paul.
Is your HT lead copper?
Is your plug cap resistive or straight through?
Is your plug resistive or not?[/quote
I dont know which Paul you are talking too.
My HT lead is a carbon core
My plug cap is not resistive
My plug is not resistive

[Paul_from_Thornbury]

This is Paul who posted originally.

It's a copper HT lead that comes with the Lukas
Resistive plug and cap. Although I find it makes little difference to the SIP speedo if you run resistive or not.

Without going full DC which I guess should be my ultimate aim but I just haven't time to get that sorted ahead of Teignmouth.

As stated I'm now back to the scooter harness being full AC. The AC is also supplying an Intelliconverter to give a good DC for the SIP.
I've fitted a battery which is charged by the BGM regulator DC output. This battery is only supplying power to the Lukas.

I will be speaking with Readspeed tomorrow to discuss.

[Fast n Furious]

You only need one resistive component in your HT line.
Any more will result in a poor spark.
I suggest that you change either your plug cap or plug for a non resistive type and see if that makes any difference before delving any further.

[Paul_from_Thornbury]

ok thanks, Readspeed suggest pick up alignment may be an issue.

Standard CDI and LT coil may have had more tolerance on alignment than the Lukas.

[Fast n Furious]

Yes.. Quite possible.
The best way to check is to use an oscilloscope attached to your red wire from the stator. Unfortunately these instruments are not part of most peoples tool kit.
If it is misaligned, then the positive going pulse will be higher or lower in value than the negative going one. Adjust the pickup until they are both equal.
Also make sure there is no corrosion in the receptacle connector at the end of the red wire. A high resistance connection here can throw up some right head scratching moments.

[Paul_from_Thornbury]

I can do that, I can borrow a scope from our measurement guys at work.
I used to be a Flight Test Instrumentation Engineer in my earlier career.

[HxPaul]

The best way for checking alignment is to draw two lines on the side of the pickup in line with the sensers,and the same on the flywheel in line with the crossover points on the magnets.You then rotate the flywheel until it reaches that point and look through the window on the flywheel and see if they line up.

[Adam_Winstone]

The Lukas CDI can retard a couple of degrees from the previous static firing point with standard CDI, with the idea being that it should be a straight swap and on the safe side. However, if you were already running little advance then a couple of degrees could now see this retarded to the point of not burning off the mix at higher revs. Have you strobed the motor to see how the firing point compares with the previous setup?

Adam

[Fast n Furious]

I can do that, I can borrow a scope from our measurement guys at work.
I used to be a Flight Test Instrumentation Engineer in my earlier career.

Ahh good.
Let us know how you get on.