OP
UTC

Member
Vespa ET4 (Pre-Leader)
Joined: UTC
Posts: 6
Location: London (UK)
 
Member
Vespa ET4 (Pre-Leader)
Joined: UTC
Posts: 6
Location: London (UK)
UTC quote
Hi all,

Pretty new to these forums so please bear with me if I do anything wrong...

Have a 98 pre-leader ET4. Sometimes runs, sometimes doesn't. Was driving along, stopped the bike for a minute or so, then would not start up again. Tried both kick-start and electric start, nothing. Waited a few hours after wheeling it home, started okay. Happens every time I run the bike, never dies while running, only if turned off and restarted. When it's being a pain, I've checked the spark plug by taking it out and turning the engine over whilst the plug is on the engine block and there's no spark. Engine turns and it sounds like it kicks, but no combustion. Also, smells like fuel so no problem with the fuel getting into the engine.

List of things checked so far:

- Battery (ok)
- fuel lines + carb jets (ok)
- fuel tap (changed)
- Spark plug (changed),
- HT coil + lead + cap (changed)
- autochoke (changed)

I've also visually inspected all the ignition cables and switches, which seems to be okay.

I think the next step is to change the CDI box, but I'm unsure as I've already done a bit and don't fancy getting disappointed again...

Any advice would be welcome. This has been happening for about 4 weeks now and i'm a whisker from scrapping the thing.
UTC

Molto Verboso
portofino green GTV 300
Joined: UTC
Posts: 1410
Location: w.ma. Northampton
 
Molto Verboso
portofino green GTV 300
Joined: UTC
Posts: 1410
Location: w.ma. Northampton
UTC quote
I would check valve gaps, the exhaust may have closed up.
@jimc avatar
UTC

Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43686
Location: Pleasant Hill, CA
 
Moderaptor
@jimc avatar
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: UTC
Posts: 43686
Location: Pleasant Hill, CA
UTC quote
I'd be wondering about the CDI as well. I'd try using some freezer spray (that plumbers use for freezing pipes) for a few quick squirts on the CDI to cool it off. If it then starts, you have your culprit, and can replace it with confidence.

e.g. https://www.cromwell.co.uk/shop/lubricants-and-chemicals/leak-detectors-flawfinders-and-freezer-fluids/freezer-spray-400ml/p/AMB7010750T

or https://www.wickes.co.uk/Wickes-Pipe-Freezing-Spray---240g/p/424922

Heat-related faults are not uncommon in automotive electronic units (often just a dry joint), and some components do not age well especially in potted devices.
OP
UTC

Member
Vespa ET4 (Pre-Leader)
Joined: UTC
Posts: 6
Location: London (UK)
 
Member
Vespa ET4 (Pre-Leader)
Joined: UTC
Posts: 6
Location: London (UK)
UTC quote
flyangler - Not sure what the valve gaps are? does this require taking the housing off the front of the engine? I've heard that the reed valves in the carb could cause a similar problem to this, but haven't checked those yet.

Jimc - Might pop to the shop or try an ice pack in the morning and see if it fires up. This would be the second time the CDI would have gone if it is that, unfortunately only have the previous duff one to compare with.

Although now the red engine oil light is coming on and off when trying to start it (even though there's plenty in there)... The never ending plot again thickens...
UTC

Hooked
carnaby 125
Joined: UTC
Posts: 144
Location: uk
 
Hooked
carnaby 125
Joined: UTC
Posts: 144
Location: uk
UTC quote
if I was you once its running is get sold and buy something else

if it costing you more then what it worth don't keep it
OP
UTC

Member
Vespa ET4 (Pre-Leader)
Joined: UTC
Posts: 6
Location: London (UK)
 
Member
Vespa ET4 (Pre-Leader)
Joined: UTC
Posts: 6
Location: London (UK)
UTC quote
Update: changed the CDI unit and it seems to be running okay... We'll see for how long.
Gave it a clean and uploaded a pic as thanks for your help!
Forum member supplied image with no explanatory text
@michaelg avatar
UTC

Hooked
ET4 187
Joined: UTC
Posts: 324
Location: Germany
 
Hooked
@michaelg avatar
ET4 187
Joined: UTC
Posts: 324
Location: Germany
UTC quote
She looks great!
I'm happy you invested a bit to let it run again. The pre Leaders can mount up amazing mileage.
@dirtydrew avatar
UTC

Hooked
vespa et4
Joined: UTC
Posts: 103
Location: San Francisco
 
Hooked
@dirtydrew avatar
vespa et4
Joined: UTC
Posts: 103
Location: San Francisco
UTC quote
Mine will sordove do the same thing too. My connector to my coil or even my spark plug wire will back out once and awhile.
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