TV 175 Will not start

[Littlewheels]

All wiring in headset is correct.

Have spare TV engine so going to take the stator off that.

[lofty]

i would also consider trying a different flywheel..

it has the classic symptoms of a demagnetised flywheel..

[Triffid]

I agree. The symptoms you describe where the engine stutters and dies when the lights are switched on are linked to demagnetised flywheel. Remove it and take it to a Lambretta specialist with fluxmeter. It can then be ascertained if the flywheel is demagnetised or not, a problem more common with the earlier brass flywheels. Some dealers may be able to remagnetise the flywheen ( if they have the right equipment) if the problem is indeed one of demagnetisation. TTFN

[Adam_Winstone]

The old test for this, documented in various texts, is to close up the spark plug gap so that the spark has as easy a task as possible. Whilst we all normally scratch our heads as to why the lighting influences the ignition, being two separate systems, this is a test that really does work, having experience it many times myself.

[dickie]

The old test for this, documented in various texts, is to close up the spark plug gap so that the spark has as easy a task as possible. Whilst we all normally scratch our heads as to why the lighting influences the ignition, being two separate systems, this is a test that really does work, having experience it many times myself.

The coils are separate but the magnets are shared between the 2 systems. A magnet produces a fixed total amount of flux, so if the magnet is weak, maybe the lighting load on it is sufficient to deny the ignition coils of sufficient flux to provide enough energy for a high voltage spark and cannot jump as large a gap?

[Littlewheels]

Update:

After replacing the stator and getting the flywheel remagnetised I managed to get the engine running but sadly too late to set off for Woolacombe

Today I took the scooter out for it's first ride. It started ok but felt like there was too much vibration and after stopping for 15mins for a coffee it refused to run & when it finally fired up it cut out when I turned the ignition key to 'lights on' position

I must mention that this engine had previously been overhauled before my ownership however after a seizure and consequently a strip down I discovered that the wrong crankshaft had been fitted (107mm), a cheap pattern piston and an Indian barrel.

Therefore I decided to rebuild it as close to original spec as I could as I wanted to experience what a standard TV175 engine ran like especially as I had been told that they were the smoothest engine Innocenti had built. I fitted an original 116mm crankshaft, Borgo piston, and an original barrel albeit now 181cc due to a rebore. The ignition also I had decided should be as it left the factory, DC with battery using the heavy brass flywheel as I had also heard that this added to the smoothness of the engine.

So you can only imagine therefore my disappointment today when I felt all that vibration! I will say though there is quite a lot of play in the handlebar rods which obviously doesn't help matters but even so I just thought it would be a lot smoother

Plan is to replace ignition switch, along with the handlebar rods and maybe change to electronic ignition.

Can anyone tell me their experiences with running a standard TV175 engine

[Fast n Furious]

I think you need to determine if it's the magneto or the scoots wiring here.
Try this:-
Disconnect both of the stators yellow wires from the regulator.
Take an old gash car headlamp bulb and connect one yellow wire across both the dip and beam connections.
Run the engine.
Touch the other yellow wire to the bulbs common point.
If the engine dies, then it's a magneto issue. If it doesn't....... then its a regulator/ wiring problem.

[Warkton Tornado No.1]

The TV 175 engine was the smoothest of all SIII’s in my opinion, so the vibration experienced is not the norm. Presumably the crankshaft is running true……

If you fitted a new woodruff key - to the freshly lapped in crankshaft taper to suit the replacement flywheel - did you check that it allows the flywheel to ‘fit’ & is not too high?

[Littlewheels]

Hi
Yes crankshaft was balanced by myself and ran spot on. Didn't lap the flywheel in as I am waiting for another to return from Scooter Surgery as the remagnetising machine has packed up I sent another (no so good) to another dealer for the same thing and I'm using that until the forever one comes back.
After a couple of days thought I've decided to replace the coil as I used the 60yr old one, the ignition switch for a genuine Osam, and rebuild the handlebars so they dont vibrate as much. Hopefully then, it should improve matters

[Littlewheels]

Update:
Rebuilt handlebars and everything looking good.
Replaced coil with CEAB
Had better flywheel remagnetised and fitted.
Re set timing and points
Started ok but still doesn't run as it should with misfiring more pronounced with lights on position.
Plus lights very bright but then halogen headlamp bulb blew (6v 25/25w) on high beam then dipped
Coil was wired with green wire to + positive and earth wire to - negative

Read that making the spark plug gap smaller can fix so set to 0.4mm
Also read a review of the CEAB ignition coil and that after fitting someone had similar problems but were fixed by reversing the wiring I.e. earth to + positive and green to - negative terminal!
Did this and now runs ok even with lights on however headlight bulb still blew with new standard type (again 6v 25/25)
Thinking that remagnetised flywheel causing too much power so thought about changing to 6v 35/35w or 12v 25/25?
Running a 12v 21/5w rear light bulb

Any help greatly appreciated

[Littlewheels]

Update:

So I did away with the new CEAB Coil and replaced it with a Vespa type coil with similar output and she started first kick and rides without any probs

[Storkfoot]

Great news. Fingers crossed, it stays that way