LCGB Forums

Last fill up before leaving Helsinki, pulled away from petrol station and it came to a fuel starved halt. Petrol tap was on, it started again and ran as normal. 2nd fill up in Germany same thing but wouldn’t start, put tap in reserve position and it started and ran as normal. When it came to fuel at reserve level in tank it wouldn’t use it despite tap being in reserve position. Used Jerry can as my reserve from that point.
Associated with all this I assumed at the time was a mid range splutter and misfire at the time I associated with the tap. It got so bad that I stopped and changed the tap, all seemed fine for a while apart from occasional mid range spluttering.
All the time it was doing this it would run happily at higher revs. Tried tests with and without fuel cap to rule that out.
Leaving Magny Cours it started again, until about 3 hours into the day when it came to a complete fuel starved stop.
I cleaned carb, checked fuel flow, checked spark, put it back together and it ran like a dream for 2 hours. Then on one occasion it got close to reserve fuel, it started again and again I persevered for an hour until came to a complete stop again. It would start, but not rev out.
I left with a nearby house for the night and went to hotel and came back to it in morning.
That night thanks to LCB and LCD pick up and transport was arranged.
While waiting I did a load of checks, including fuel flow rates, started and seemed to run ok but there’s something just slightly amiss.
It’s a TS-1, running SIL stator but no LT coil. Tambs CDI/Coil supplied directly from battery. Standard pick up and Tambs external pick up.
It’s on its way home a day or so behind me. I’m on a ferry home currently.
First port of call will be CDI/Coil I assume, but it had a spark every time I stopped, if those fail is it not normally terminal, it doesn’t explain the 2 hours of perfect running on the Sunday. What about reeds? I replaced them this winter as the previous set had been there a while but were looking ok.
Any thoughts gratefully received.

Reeds tend to fray then let go so performance wouldn't come back, only deteriorate then fail.

What carb and how old is it?
I ask because as I was about to leave the euro on Saturday, my scooter wouldn’t rev out and was a pig to start. Seemed electrical even though it was sparking.
Methodically went through and replaced plug, plug cap, ht lead and cdi. Obviously one thing at a time.
Eventually it wouldn’t start at all so general consensus was either stator or reed petals.
Took petals out, some were feathered and one set wouldn’t close. Thought we’d cracked it……
Replaced reeds and still wouldn’t start or even fire.
Next change was stator but I wasn’t convinced. No different.
Anyway, happened to have a new carb with me so thought nothing to lose trying that before taking the barrel off. Put it on with the old slide and needle so didn’t have to mess about with throttle cable.
Started first kick.
Left on Sunday morning, couple of plug chops and needle change and then did 430 miles and got home Sunday evening.

/\/\/\ that's a good call

Never had it on bretta but, those symptom are very evident when the Vespa SI carb is failing , don't know what it is but it does happen.
The Spacos going quicker than the genuine dellortos did.
Have experienced it on my own and a friends bike, luckily from him i`d gone through the pain.

It’s a Dellorto VHSH30, and I guess about 7 years old.
My issue with this suggestion is that starting isn’t a problem, revving out most of the time is not a problem.
It’s the riding along after 2 hours with no worries at all, then all of a sudden the mornings problems start again. When it’s returned my first port of call will be CDI/ Coil. Cannot be stator as I don’t use LT coil. Both internal and external pickups work.
Just be good to know people’s thoughts on CDI/ Coil, can they have intermittent periods, then be faultless, then faults return. My thoughts are no.
My fuel flow is good, but when it dies it feels like fuel starvation but it could be the spark just stopped.
But as soon as I test for spark it’s good.
It’s a new fuel tap, and flow is acceptable.

No harm in trying a different carb.
A friend had similar symptoms with a Dellorto, changed carb and all good.
Your symptoms are very similar to mine. After all, I’d done 750 miles getting to the Euro with no trouble, easy starting, revving out fine etc.
Pretty rare for cdi to fail these days. Same one on mine for 17 years. Have had plug cap fail though….

Had this sort of problem myself some years ago.
Turned out that I'd filled up with some dodgy fuel that had a lot of water in it.
Leave the scoot to settle over a few days and then shine a torch into the tank. if it has water in it, then it tends to settle as a noticable glob on the bottom of the tank.

Any update Paul?

Not as yet. On holiday.
When it arrived back at port in Helsinki, it ran like a dog home from port. Started no problem, but any revs just above idle it’s coughing and spluttering. But when given more throttle it seemed to run better.
Did one thing before leaving, fitted a new float valve and thoroughly cleaned carb. Now it won’t start at all.
With centre plug head it’s a shock off to check spark and I couldn’t be bothered. So I’ll do in a week or so when home.

Ahhh the joy of Lambrettas!

Fast n Furious wrote:Had this sort of problem myself some years ago.
Turned out that I'd filled up with some dodgy fuel that had a lot of water in it.
Leave the scoot to settle over a few days and then shine a torch into the tank. if it has water in it, then it tends to settle as a noticable glob on the bottom of the tank.

This was my thought too especially as it seems to hapen when the fuel is low. I;d drain ut into a clean clear container

Ok, she’s running. My switch between internal/external pick up wasn’t quite switched in position, hence she wouldn’t spark/start after I cleaned carb last week. So it looks like it could have been the float valve/needle as that was a suggestion by Martin Ollman of LC Deutschland, the symptoms certainly suited that. Carb has been thoroughly cleaned too. Tank is nearly full and I don’t have enough Jerry cans to empty. When we are back at home next week after holiday I’ll ride to empty the tank to check there’s no water in bottom and give fresh fuel.
But I’ve just run up the road a few times and she revs cleanly to 8000.

Sounds like you've solved it...

Nope, it’s gone again. Ran fine for 70km today. Went into reserve. Was ok, then started the misfiring and cutting out again. Checked fuel flow on reserve, all ok. Drained what’s left of the crap French fuel and put in fresh and it’s the same.
Stripped carb again, all ok.
But will start then just stop. Will start and run for 100m then stop.
I have no idea now at all.

Have you taken the petrol tap apart to have a look at the insides at all Paul?

Tried adding some fuel so it’s above reserve and running on main fuel position but it still hesitant and dies at a junction.

It’s a new tap fitted on way to Magny Cours. It flows the right amount on both positions.

That rules that out then. What about a hole in the carb float? Also, had you been inside the carb shortly before the problem started? If yes, could the float adjustment have been accidentally changed?

Got a friend coming next week with a Vespa 50 tank to put on seat behind me. Going to rule out my tank, tap and fuel pipe in one go.
I’ll stick a borescope camera attached to my phone down inlet also on Monday to check reeds.
If I get chance I’ll fit new CDI/Coil before all this just to rule that out, but I’m sure it’s not electrical issue.
One suggestion above was a complete new carb, thoughts on this, it’s all been cleaned out, all jets are clear, it runs fine for ages and then I get these periods of poor running. Not sure what new carb body does for me. Plus it’s over €200 for a new VHSH.

Random thought. You mention changing the needle valve. Did you change the float needle too?

I know on a PHBH/PHBL if you go from, say, a 2.0 to 3.5, the needle is a different profile.