Starting Problems

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
Blenks
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Joined: Thu Feb 26, 2015 1:29 pm
Main scooter: Lambretta S3 Li150
Location: Coventry
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Mon Jul 02, 2018 10:46 am

Since the rebuild of my Li150 I have been having intermittent starting problems. I have had the carb cleaned and a new air filter fittted. I was shown pictures of the crap that was removed from the carb so thought that would sort it. Also had an ignition key fitted to replace the kill switch. I don't think it is that because I had the problem when the kill switch was still fitted. It starts first kick usually and runs really well - BUT, when I stop and try to restart there is nothing. Stopped yesterday at a mates after doing about 5 miles and when I tried to start it seemed dead like there was no spark. I even tried to bump-start it but nothing. Gave it a minute and tried to kick it over again and it started no problem. I know the plug is OK but had this issue now for about 6 weeks. I can't suss out what it is and it has been in to a repair shop twice with no joy. Really frustrating because when it's running it is spot on. The ignition switch that was fitted is a CASA one so hopefully it is a good one. Any suggestions???

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garry inglis
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Mon Jul 02, 2018 11:34 am

check your earths are all tight there is three main earths rear light headset and frame to regulator and coil also spark plug cap ht lead is tight in cap and coil

Blenks
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Main scooter: Lambretta S3 Li150
Location: Coventry
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Mon Jul 02, 2018 11:47 am

Thanks Garry. The earth fixings were my first port of call and they all seem good. Also tried a new plug cap and plug. Not made any difference. Just strange that it starts no problem initially but there is a problem if I stop and try to restart when the engine is warm or has been run for a while. May revisit the earths though and check that there is enough paint removed from the contact points.

mick1
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Mon Jul 02, 2018 2:18 pm

Try starting with bellows removed. Sounds like fuel could be trapping and causing it to flood

bristolmod
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Main scooter: Lambretta TV175 S3- what else!
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Mon Jul 02, 2018 3:12 pm

I assume you have the "new" bellows without any drain system? Innocenti dropped the drainage system round about 1967 to save costs, but the "new" system can allow fuel to gather within the bellows as Mick says above. I tend to put a very small hole in the lowest point of the bellows (1 or 2 mm) to allow excess fuel to drain away- doesn't affect the running at all and generally works

Chris
Scootering since 1968.

Blenks
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Posts: 161
Joined: Thu Feb 26, 2015 1:29 pm
Main scooter: Lambretta S3 Li150
Location: Coventry
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Mon Jul 02, 2018 6:44 pm

Thanks For the replies folks. There is no drain off on the bellows I have fitted. I’ll check for fuel in it when I get a chance and try starting with filter off. Anyone tried the tea strainer type that MB sell. I don’t want to have to cut holes in the side panel. I have a larger fuel tank so the filter and bellows get squashed a bit when the panel is fitted. Could that be a cause???

Blenks
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Posts: 161
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Main scooter: Lambretta S3 Li150
Location: Coventry
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Thu Jul 05, 2018 8:22 am

Just for clarity I have a 186 Mugello fitted to Li150 engine and have a Dellorto PHBH 30 carb. I had an elbow bellows with a foam filter (ram air type) but when it went in to the repair shop they fitted a cone paper type filter on to the bellows. As I have a larger fuel tank and no air box I have to have the filter at 3 o'clock rather than pointing straight up as there is very little space between tank and tool box. The filter does get pressed against the side panel when it is fitted. I have read a bit about spit back and wondered whether the tea strainer (metal grille) type filter that fits direct to the bell mouth of the carb would be better and if it would help with the collection of fuel in the bellows as in affect there would not be a bellows fitted. MB have one and it states it is "the only air filter you will ever need". Anybody used one or one similar?

My other thought may be that it could be the choke. I fitted a new cable when I rebuilt it and had to shorten the cable slightly. I have read again that the choke may be slightly opened as I sit on the scooter due to suspension movement. I have noticed that the engine seems to tick over faster. I will check this at the weekend when I get a chance.

HotPearlSnatch
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Thu Jul 05, 2018 12:00 pm

Hey Blenks, okay, if you're running a 30mm dellorto it should run fine without any filter on there, if your filter is fouling the panels [when they are on] you could be constraining the air flow into the carb. Just take the filter off entirely and try that. You might need to richen the mixture on the airscrew a touch also.

If your bike is ticking over quicker than usual [or you like] then it is either running too lean [and that could cause starting problems on a warm engine], or your choke or throttle cable could be too short and that could cause it to run rich [usually bogging down if its the choke though].

I am guessing you have an electronic ignition on this bike right?

I have had significant problems with some indian pick ups lately and i suspect here is a sea of crappy fake K2s out there [because i seem to keep buying them!].

Much of the issues i have had i *thought* were carb but in fact turned out to be ignition and in a couple of occasions the bikes starting deteriorated prior to the ignition giving up completely. If you have a spare stator then maybe try that, better still if you have a mate with a spare BGM then try that. I got a BGM V4 [older version] off eBay for 40 quid, excellent ignition in comparison to the SIL ones that have given me so much trouble of late.

Finally [and this will cause an uproar] i ditched my dellorto 30mm for an AMAL MK2 30mm and my fuel problems disappeared. The dellorto carb is a much lighter casting than the old amals so fuel CAN evaporate out of the carb quicker [as the motor and carb get hot]. The Amal is a way heavier casting so dissipates heat more evenly....just a hunch.....worked for me.

Good luck and please do report back.

Blenks
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Main scooter: Lambretta S3 Li150
Location: Coventry
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Thu Jul 05, 2018 12:29 pm

Thanks for the advice and suggestions. It is a 12V electronic ignition and it has a BGM stator fitted. Was on when I bought the scooter about 3 years ago so not sure how old it is. I'll definitely give it a go without the filter fitted tomorrow and report on how it goes.

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HxPaul
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Thu Jul 05, 2018 1:16 pm

When it refuses to start,have you checked for a spark ?

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