LCGB Forums

Hi all,

I am relatively new to the scene so please bare with me.

I have a series 3 li 150 with an rt 195 kit, 30mm dellorto, Ducati 12v system,bgm clubman pipe and has had a full engine rebuild.

I’ve done 112 miles on her, no issues but now she refuses to start. I’ve changed the plug, cap and bgm cdi and still no spark....

Any help very much appreciated

Cheers Alan

any loose wires or wire ends @ CDi?
whats your stator readings?

Prior to any other action, you could eliminate any non-essential components toward checking for spark generation:


Disconnect any shorting device from the CDI (traditionally the green wire that goes to the headset key/kill switch)

Connect a supplementary earth from CDI to magneto housing temporarily .

With no other than a well connected HT lead from the CDI (no plug or cap) turn over the engine & see if a spark, or flash, is apparent with the HT lead in close proximity to the new supplementary earth where it connects to the CDI.

Leap for joy if you get a spark/flash/belt up your arm.

'Monk' for the rest of the day if no result. Consider joining a monastery/convent.


That procedure will @ least narrow the field (no pun intended) & signify where to go from if a spark exists, or not.

Good Luck & welcome to Lambretta World! Consider this test as part of the initiation process, which for many of us never ceases over many decades.....

Sometimes a spark is hard to see.......bite the bullet and check by touching the plug when kicking over....painful but eliminates quite a few things.

If you get no shock then check as stated above.....also possible issue with pick-up height,

Thanks to all for the response,

Ran a few checks,

White terminal to mag housing 0.9-1.2
White terminal to green lt 470
White terminal to red 93.8

I presume there is a fault with the lt power coil at the stator?.

Should be very little or next too nothing on the white earth mag wire
The rest are in range

As Warkton Tornado said, the kill function is a VERY common cause of loss of spark and should be tyhe very first thing to check, There are two green wires in the CDI, one comes from the stator and the other goes into the main loom and runs up to the headset kill button or switch. Disconnect this wire from the CDI and see if you get a spark before doing anything else. Just to explain, the ignition is on all the time and the function of the kill switch is to short the ignition feed to earth. Sometimes the insulation in the switch breaks doen and applies a partial earth, this is more common with Indian sourced aftermarket ignition switches but can happen to the button type too, especially in damp conditions.

Yeah I’ve taken out the kill switch wire at the cdi and she still won’t fire up.

Remove the spark plug.
Use a multimeter set on the 200V AC setting. (An analog meter works best here.)

Temporarily disconnect the green wire in the terminal block (the one that goes up to the ignition or kill switch) and keep the green connection to the CDI.
Connect your black meter lead to the chassis and red meter lead to the green wire terminal at the CDI
Kick the bike over and you should see the meter peak at around 60 volts AC.
If the meter reads next to nowt, then most likely the LT coil on the stator has failed. (An extremely common problem)
It could also be the pickup coil that is the culptit, but these are difficult to diagnose correctly without an osciloscope. Very often these coils just get replaced adhoc when everything else checks out.
Truth is........ resistance readings of the coils usually proves to be a fruitless task.

I've huffed and puffed with similar, it'll be the stator for sure. Best just get a new one, if it works great, if not you have a spare. I spent a week looking for a fault with a multi-meter too, stator measured ok, was getting a spark but breaking down under load. Best cut to the chase and whip it out. G

Pick up height is what I have found causing problems. Remove the flywheel, Check the Woodruff key is intact. Find the 2 silver metal strips on the face of the black pick up and with a white or coloured pen draw the position of the strips on the side of the pickup. look at the inside edge of the flywheel and you will see the join between the 2 magnates. the firing point. Refit the flywheel and looking through the window turn the flywheel so you can see the join and also does it line up with the 2 marks on the pickup. Often the pickup is 3mm too deep. BGM was supplying a spacer to fit under the pick up to line them up. Often the stator is fine but too many slight changes with positions even on Brand new parts. The air gap between the pickup silver strips and the magnates can also be a problem but not so much.

check also that the flywheel hasnt worn thru the top of the black pick-up due to incorrect alignement of flywheel & pickup
I had a Ducati flywheel still firing ok for a couple of hundred miles then nowt,