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Has anyone got any experience of wassel units interfering with ignition at high revs? I have got a fairly high spec TS1 that wants to rev high, but with the wassel connected splutters badly, disconnect the power.....runs like a dream!

I have tried different, stators and cdis, a new wassel, disconnected the lights, speedo etc, I've move the wassel well away from the Cdi, nothing makes any difference?

It' s also possible that this issue was responsible for a string of unexplained seizures on a previous build.

Any thoughts?

im a big fan of scootronic products, i presume you have a standard type stator, i would add an external pick up and see if it cures your issue, they do also make a cdi unit that doesnt use the standard low tension coil, can be used as the main ignition system and have the internal coil and pick up as a spare, ive got the whole lot on my rotax conversion, running it direct from the battery to get a big fat spark, makes good power. if i had to guess i would say your problem is pick up alignment not quite where it should be, bgm stators are well know for this issue, they even come with packers for the pick up.

Have you tried it with a different flywheel? could be a bit weak magnetism wise, also, what happens to the ignition voltage when it starts misfiring?.

Thanks for the replies chaps,

I definitely get the Scootronic set up, could be a good solution, I have tried a number of different stators, and did try a known good stator flywheel combination.

I'll test the low tension voltage at the weekend

Earths can make a huge difference to electrical noise suppression

Have you checked that that wassel is earthed to the frame and that is continuous to the engine body?

I've got good quality earths from the vassel/Cdi earthing points to the engine and over to the mag housing, resistance reads 0 on a decent multimeter. Battery voltage is constant 12 v dc, voltage across the stator/vassel connections is 12 to 13 v ac and stays consistent through 7000 revs when the spluttering starts, once again, disconnect the yellows and she's the best running scooter I've ever owned.

Just a thought, and I don't really know what difference this would make, but if your stators have been converted from AC, are both yellows isolated from earth?

Both yellow stator wires isolated from Earth.

I've now converted to ac, as I want to ride her over to Ypres, Might investigate further at a later date.

You haven't mentioned what stator you are using but 12-13 volts at 7k RPM sounds a bit low, I get 14 volts from about 5k upwards using a BGM and a Scootronics stator. If the problem goes away with it converted back to AC then it has to be the wassel regulator at fault.

Stator is BGM, Wassel unit is brand new (BGM) but demonstrated exactly the same problem as the previous one.

The problem was discovered on a dyno tune, we couldn't work out what was causing the high rpm spluttering and generally lower than expectated performance, almost by chance we disconnected the power side and discovered that this resolved the issue. Various stators and flywheels were tried And in the end a new wassel, I have tested wiring to death and even bought a new ignition switch in case there was power to ignition interference there.

The engine is a fairly high revving TS1 on a TSR pipe, 30+ BHP with healthy low down torque, as I said the best running scooter I have ever owned........until you connect the yellows! Weird

Back on AC for the foreseeable future, but would be interested to hear if anyone else identifies similar issue. it could be quite subtle, costing a HP or 2, but also I am suspicious that the associated running issues may have caused excessive heat generation and led to dual carriageway seizures on previous builds.

The person you need to talk to is Anthony Tambs, he doesn't come on here as far as I know but he is on Face Book under Scootronics. What that guy doesn't know about Lambretta ignition systems isn't worth knowing

What is the retard unit?

Well, hat of to Mr Tambs.
Removed the large grounded copper washer on the Low Tension core as suggested by Anthony & problem solved!
Back on DC running like a dream.

Bobs2 wrote:Well, hat of to Mr Tambs.
Removed the large grounded copper washer on the Low Tension core as suggested by Anthony & problem solved!
Back on DC running like a dream.

I told you he knew his stuff