Varitronic/cdi fault?

[Cheersdude]

hi all. A few weeks ago my engine cut out at speed. Thought it was the spark plug as I couldn't see a spark but it was a bright sunny day so was a bit hard to see. Tried another plug and could see a spark with that either. Fitted it anyway and remade the ht lead and it started and got me home. Since then I've been out on about a 70 mile round trip with no problem apart from a little splutter, again at speed. I eased off the throttle and it was fine the rest of the journey. It thought this might have been down to jetting, as its jetted for running in and this was the first time I'd pushed the speed over 70.
It's sat for a couple of weeks, I took it out the other night. It was hard to start and after about half a mile it cough,splutter and cut out. Check the spark plug again and there was a spark but not very bright. Managed to get it start, went about 100yards and it done the same again.
Got it started tonight and had it ticking over for a few minutes before it cut out and wouldn't restart. I got my megger out and tested the resistances, but I'm not sure what reads I should be getting and whether I'm tested between the correct wires. Here's what I got I tested each wire to the engine mount(basically to earth)
Red/black 0.7 ohms
Yellow/white 2 ohms
Red/white 0.9 ohms
Blue 0.6 ohms
I disconnect and reconnect as I went so these reading may be totally useless!
I'm leaning towards the stator or the cdi as these are the only 2 secondhand parts fitted. Though I'm open to suggestions. I've try removing the green wire from the cdi but it makes no difference. And I'm gonna try a different ht lead and cap at the weekend.

As ever any help greatly appreciated
Cheers. Jon

[Wack]

Compared to other systems the Varitronic seems to have a weaker spark but your readings seem strange. To test the LT coil, red/ black wire,with the meter set on 2k you should be getting 290 ohms give or take 20%. Blue is earth with low resistance. Check all earth points for CDI and that the engine has a good earth to the frame and that your terminals are sound.

[johnnyXS]

it might be worth checking the wire to your coil is not loose or shorting out somewhere .
Mine coughed and spluttered for miles and finally conked out on the way back from the MOT the other day . I suspected fuel delivery but eventually tracked it down to a taped tempoary joint I'd made on the stator- to- coil wire which was intermittently shorting out to the rear mudguard.

[MickYork]

sounds like you've tested with everything connected. disconnect all stator wires and re-test.

Cam-lam have some technical data on there site about the Varitronic.....might be worth a look or try e-mailing them with regards correct readings........if you try calling them good luck !!

[dickie]

I wouldn't test with a megger. You're likely to damage components if you use it on the low tension side.

It can also give very different readings to those you get using a multi meter so will be unhelpful when making comparisons

[Meds]

Try searching the forum under Varitronic Help , there are a couple of useful links

[Jamjo]

Some details here for readings

[Nobby]

Iv got one of the very first varitronics and its done 10000 + over about 12/13 years?, but last year it started to get hard to start but started ok with a new plug, then after a while ( I went to the iow on it, local ride outs) it started to cut out every now and then and a new plug would solve it, like you I redid the ht lead, cap, earths , connections etc thinking it was a fault in the external wiring, and like you I did the multi meter readings of the stata which showed they were only slightly under.
However when I rang round it seems varitronics arnt as indestructible as I thought and the statas do fail- not commonly but it does happen and a lot of the main suppliers do keep spare statas in stock -speak to armandos or Mike Phoenix or Camb lambretta, I changed mine and it totally cured it..... Think I new stata is £100?

[Gary Harwood]

A mate of mine and I were going to France for a long May bank holiday weekend. We both have Varitronics fitted to our Lammies and both have Mugello 186 kits. We left Cambridge early morning and stopped for breakfast about 10 miles into our journey south. As we set off again my mate's scooter spluttered and lost power for a couple of miles then cured itself. It behaved well from then on until we stopped for lunch at Strood in Kent. After lunch his scooter wouldn't start and we thought it was plug HT lead or choke stuck on. Having changed plug, HT lead and fitted new choke cable it started and we rode the rest of the way to Folkestone with no problems. We stayed overnight near the Chunnel as we were booked on a very early train to Calais the next morning.

The next morning we were up bright and early, scooters loaded but, once again, my mate's scooter wouldn't start. After 4 hours, and trying everything we could think of, we gave up. Carole Nash was called. Our French holiday was off (or so we thought) and I left my mate in Folkestone to wait for the recovery truck while I rode back the 140 odd miles to Cambridge. We had decided to have the recovery truck take his scooter directly to CamLam. Coincidently both the recovery truck and I got to CamLam within minutes of each other. Trevor from CamLam confirmed we had tried everything except the stator and suggested we fit a replacement. After a little over an hour we had fitted a replacement stator (supplied by CamLam for a little over £100) and....bingo.......it started first kick. My mate rode it to my house (about 20 miles from CamLam) and it performed impeccably.

I have a van so we quickly made another Chunnel booking for very early the next morning. Loaded the 2 scooters and our gear into the van, got some food and rest and then set off shortly after 4.00 am for the Chunnel. We eventually got to our original destination in France about half a day later than originally planned. The holiday was rescued. Wehad a great time riding the Lamies in France and we had no further problems whatsoever. So yes Varitronic stators do break down and we learned a valuable lesson........be prepared to change one on long trips. Good luck with fixing yours.

[bike grim]

Sorry to hi jack as I can't assist in the diagnosis but just out of interest how are you changing the Ht lead as I thought the ht lead was molded on to the cdi box on the varitronic. I only ask as I have a cdi without a lead that I presumed was junk. If I can fix it I'm all ears!

[Cheersdude]

Thanks for the replies. The megger is a multi meter, just maybe a little industrial for the job. But has an ohms setting, though I did think after testing that reconnecting as I went would give me false readings (should know better as I am a sparky!) I'll check again tonight.
As to the cdi mine doesn't have a moulded lead, I just screwed it in, like u do to a ht cap.

[Cheersdude]

I had another check tonight, I disconnected all the wires from the stator. Checked the resistance between red/black and earth and got 207ohms. And blue to earth was pretty much a short circuit which it should be. Am I right in thinking these readings are correct ?

Also checked the green to the ignition sw. which when the sw. is off I have a dead short and when the sw. is on I have an open circuit, which I believe is correct.

Still won't start. Will try a new lead and ht cap at the week just to rule these out.

[Captain Pugwash]

I had another check tonight, I disconnected all the wires from the stator. Checked the resistance between red/black and earth and got 207ohms. And blue to earth was pretty much a short circuit which it should be. Am I right in thinking these readings are correct ?

Also checked the green to the ignition sw. which when the sw. is off I have a dead short and when the sw. is on I have an open circuit, which I believe is correct.

Still won't start. Will try a new lead and ht cap at the week just to rule these out.

Think it should be a minimum 270 Ohms and maximum 310 Ohms, so if yours is reading 207 Ohms then it's a low reading.

[Wack]

Are you sure about the CDI as the lead is normally sealed in?

[Captain Pugwash]

I've had to removed a couple in the past, I think the HT leads are usually screwed in and glued.

[MickYork]

Megger is a brand same as a Hoover/\Dyson etc.......as long as you read on the ohm scale and don't use on the 500v setting (M ohm) you won't have a problem.

[Cheersdude]

Think it should be a minimum 270 Ohms and maximum 310 Ohms, so if yours is reading 207 Ohms then it's a low reading.

New stator then?

[Cheersdude]

I ordered up a new stator and fitted it today. It looked like a straight swap just unbolt the old one off the back plate and bolt on the new one. So I thought! It started on the second kick, but didn't feel right. Put it in to gear and shot off backwards! Wot have I done wrong? Will I need to get the timing checked?

[johnnyXS]

musn't larf.. yes it sounds like the timing is out unless you have the wrong stator
Have you got a video of it going backwards ?

[MickYork]

I ordered up a new stator and fitted it today. It looked like a straight swap just unbolt the old one off the back plate and bolt on the new one. So I thought! It started on the second kick, but didn't feel right. Put it in to gear and shot off backwards! Wot have I done wrong? Will I need to get the timing checked?

either check the timing or put the forks on the back end.....the choice is yours.

sounds like the timing is out by quite some way.....or the woodruff keys sheared and the flywheels slipped.