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Sorry to ask such a vague question but I'm in a bit of a pickle. My lambretta is 40 miles away and I need to go equipped to fix it.

Started becoming increasingly spluttery while on the dyno. Seemed to clear up but 2 miles into my ride home it became unrideable. It will start but barely runs for 5 services or so and splutters badly while doing so.

Changed plug, cap, cdi, carb, pick up. Measured lt coil resistance and output voltage (around 50v). Plenty of compression. No spitback.

So everything is perfect but it doesn't work!

The only thing I can think to do is swap my stator because I haven't tried it, but it measures ok.

Thanks to Billy with the tartan scooter and Ken (dsc?) for the excellent help with spares and ideas. Smashing fellas. I'll get you both a pint sometime.

Any ideas please so that I can take what I may need?

Has it got a reed valve? broken petals?

Leotech wrote:Has it got a reed valve? broken petals?

It's a gt186 so yes, but i don't think so as there is no spit back at all and at first it ran fine 90% of the time. I'd expect a broken reed to give consistent symptoms. Also I replaced the reeds 50 miles ago. I can't say they aren't broken as I haven't checked but I doubt they are damaged. I'll check that when I'm there.

Not very helpful - but if its only 40 miles away - are you not better cadging a van & bringing it home - especially if you don't know whats wrong with it

Looks like you've done the obvious stuff so open heart surgery seems daft when so close to home

if you've no van - try Shipley - you never know whether someone is in the area & up for a quick job

If you replaced the petals 50 miles ago is it possible they have worked loose? Just a thought.

bookertmgs1 wrote:Not very helpful - but if its only 40 miles away - are you not better cadging a van & bringing it home - especially if you don't know whats wrong with it

Looks like you've done the obvious stuff so open heart surgery seems daft when so close to home

if you've no van - try Shipley - you never know whether someone is in the area & up for a quick job

On reflection I think you're right. I might just ask the lad who has it to drop it off and I'll do it in the comfort of my own garage. I'll have to pay him but I'll save time and van hire cost.

Donnie wrote:If you replaced the petals 50 miles ago is it possible they have worked loose? Just a thought.

You could be right. They were fitted with loctite and I'd expect spit back but it's worth checking.

I've got it home now and just started looking. When I put my hand over the carb I can feel some pressure pushing my hand away from the bell mouth. Is this normal with a reed? It's not for the full revolution , and it's hard to be precise but i'd say from approx tdc to bdc. This seems like reeds to me but before I go stripping my top end to take a look I'd appreciate second opinions.

As advised above do check your reeds.
You say you measured 50v from your LT coil? I'm assuming that's 50 VAC? Only measure this on AC!
If so, this isn't enough and is a typical measurement that you will see from an iffy indian stator. If the symptoms seem to be that the scoot has developed a near perfect rev limiter then this is typical of a goosed LT coil.
Measuring the resistance of the coil won't tell you anything worthwhile. In my opinion its not worth the effort trying to fix it with spare parts. Just put a BGM stator in and be done with it. Its £40 for a piece of worthless crap and £80 for a peace of mind.
No brainer.

Fast n Furious wrote:As advised above do check your reeds.
You say you measured 50v from your LT coil? I'm assuming that's 50 VAC? Only measure this on AC!
If so, this isn't enough and is a typical measurement that you will see from an iffy indian stator. If the symptoms seem to be that the scoot has developed a near perfect rev limiter then this is typical of a goosed LT coil.
Measuring the resistance of the coil won't tell you anything worthwhile. In my opinion its not worth the effort trying to fix it with spare parts. Just put a BGM stator in and be done with it. Its £40 for a piece of worthless crap and £80 for a peace of mind.
No brainer.

Thanks. It is a bgm stator because I generally subscribe to the same point of view as you; that it's better to buy quality once!

It's not acting like a rev limiter though. It runs great for something between 10 seconds and 2 minutes then won't start for a few kicks, then it's fine again. I have a spare motor under the bench with a bgm stator that I'll try tonight if I get the chance.

Not an ignition problem. Runs really nice then all of a sudden goes flat and dies. But it takes a good 5 seconds to stop altogether. While it's cutting out I can see that it's still firing well as I had my strobe on and the spark is rock steady at 17 degrees.

My money is on stator and the stator you speak of are not the most reliable I can assure you, we done 4 new ones on our production racer last season, readings etc were fine, low tension coils over heating was the general consensus of opinion from some well respected electro wizzards.
or possibly a fuel starvation problem?

Ok then Scotty, I'll bow to your greater experience. New stator tomorrow night.

I'm certain it's not ignition but I've been certain before and then found out I was wrong.

I had a similar problem over the past week having completed winter maintenance. Scooter would start, I'd get about 100 yards and stall. Changed LT coil, swapped CDI, played around with jetting, etc etc... eventually figured out yesterday what the problem was... I fitted a new mid-range tank and tap over the winter and had filled it with about 4 litres of fuel I had in shed. What I didn't realise is that the reserve on this new tank/tap set-up is about 4 litres... turned the reserve on and it started and ran straight away. Sometimes it's the simplest of things...

I would suspect bad fuel my sons vespa had similar symptoms to yours when I drained his tank there was gobs of stuff that looked like fat so cleaned the tank put fresh fuel in and it was fine again

missing lynx wrote:I would suspect bad fuel my sons vespa had similar symptoms to yours when I drained his tank there was gobs of stuff that looked like fat so cleaned the tank put fresh fuel in and it was fine again

Interesting. I filled up 1 mile before putting it on the dyno. It was a bp garage. Regular unleaded. Never correlated the 2 things though, probably because there was an hour between them? That's 2 things to do tonight. Stator first though as it's easier. Thanks gents

dscscotty wrote:My money is on stator and the stator you speak of are not the most reliable I can assure you, we done 4 new ones on our production racer last season, readings etc were fine, low tension coils over heating was the general consensus of opinion from some well respected electro wizzards.
or possibly a fuel starvation problem?

Looks like you're right scotty. I eventually got round to changing the stator tonight and it seems good. If it's dry tomorrow I'll do a few local miles to be sure.

Funny thing it's that as well as readings being perfect it was still firing my strobe. And the firing angle was rock steady.

Not certain yet but that's the longest I've run it and it never spluttered. If it can do 5 miles it's sorted.

B**ls. I thought it was the stator but it was just teasing me. I'll repeat the symptoms:

Starts fine and will tick over until I get bored. Revs clean and crisp. I THINK it starts to faulter as I close the throttle to change gear or just slow slightly, but it's hard to be sure about that.

Personally I wouldn't expect reeds to give intermittent symptoms; am I wrong?

The carb was stripped and blown through but not by me so I can't vouch for how well it was done.

Could reeds really give those symptoms?

I'm reluctant to strip the top end as I spent ages trying to get it just right and it's covered in threebond.

I think you more or less eliminated it being the stator because I agreed (to myself!) way back when you said:

dickie wrote:Not an ignition problem. Runs really nice then all of a sudden goes flat and dies. But it takes a good 5 seconds to stop altogether. While it's cutting out I can see that it's still firing well as I had my strobe on and the spark is rock steady at 17 degrees.

To my mind, it sounds like inlet, specifically the reeds sticking/breaking down. Sorry that it’s not the diagnosis you want to hear....

Well, I took the reed valve out to inspect it. Absolutely fine.

Aaaaarrrgghhh.

I reckon it's the carb. It's been pulled apart a couple of times but not by me so I can't say how good or bad it was. Only that the chap who did it is far from stupid. The Mrs is getting irritated though so it will have to wait until tomorrow night.