Lambretta Overheating

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
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Burnside
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Mon Jul 31, 2017 10:14 am

MightyGem wrote:
Fri Jul 28, 2017 8:15 pm
TBH the weather should make little difference as standard Lambrettas sold well and ran reliably in warm climates and we've had some VERY warm weather for the last 2 Euro Lambrettas, with many riders screaming their bikes on motorways for hundreds of miles a day, without seizure.
My thoughts as well, but it's never happened on cooler days.

You're actually more likely to run hotter on cooler days than hot days as the air is denser and you run slightly leaner, but it is negligible
Out of interest have you checked the plug when it seizes
Not at the time of seizure, it's too hot. :D

I find gloves help
too little oil all can cause the motor to run excessively hot.
Mix at 32:1 (3%) EVERYTIME
I run at 4% so going down to 3 is probably not needed.
4% of what oil? For a standard set up 4% is excessive imo unless using mineral oil

MightyGem
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Thu Aug 03, 2017 7:58 pm

4% as per Lammy handbook; i.e., 25 to 1.

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Burnside
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Fri Aug 04, 2017 12:38 pm

MightyGem wrote:
Thu Aug 03, 2017 7:58 pm
4% as per Lammy handbook; i.e., 25 to 1.
A 50+ year old Lammy handbook, in which time both the petrol and 2 stroke oil you are using is completely different to what it was in 1959, 2 star and mineral oil was the standard when that was written! That is too much for a standard set up with a modern oil, 3% is plenty, 2% will be enough. I only use 3% of cheap semi-synthetic in my tuned Lambrettas

MightyGem
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Tue Aug 15, 2017 12:39 pm

Thanks for that. I'll give that some consideration.

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alcoholic maniacs sc
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Tue Aug 15, 2017 2:10 pm

Grumpy225 wrote:
Fri Jul 28, 2017 6:22 pm
Jetting is usually the culprit when it comes to heat. Too rich, too lean, too much oil, too little oil all can cause the motor to run excessively hot.

Start with the easy stuff first.

Clean your motor if it's covered in grime.
Mix at 32:1 (3%) EVERYTIME and use the highest grade fuel you can get consistently.
Run the coldest plug you can with out it fouling out, I run NGK B9ES on everything.
As mentioned before, timing is important. Make sure it is set correctly and know where its firing.
i run a standard 150 on tesco lawn mower oil and an open carburetter with factory jets, th exhaust is so blocked it weighs as much as the scooter, the ignition timing was set to " it looks about right" - flat out everywhere
standard Lambretta's were still running in southern italy well into the early 90's with no maintenance whatsoever , ditto vietnam etc
if your bike is nipping up then my guess would be an airleak somewhere or the piston is mullered..
does it tickover for long periods without stalling ?
does it start after a couple of prods on the kickstarter?
that usually tells you how healthy your iron barrel is.
ive nipped mine up 10 times in 10 years ad cant be bothered stripping it u til the thing gets too slow or something else breaks, but if i was constantly getting your symptoms then id go for a strip down, ignition timing is important on tuned bikes but a little out on a standard should manifest itself in other problems as well before seizing ....
Alcoholic maniacs social club. out f@@k,out fight and out booze 'em.

MightyGem
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Wed Aug 16, 2017 9:50 pm

the piston is mullered
Is that a technical term? :lol:
does it tickover for long periods without stalling ?
does it start after a couple of prods on the kickstarter?
Yes to both.
ive nipped mine up 10 times in 10 years
Under what circumstances?

Jeff T
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Thu Jul 05, 2018 10:13 pm

Mine packed up on Sunday Imola, not sure it's heat seizure what are the symptoms. I've stripped the cylinder down and apart from more carbon on the piston crown than I would have expected as I only rebuilt it last year, I can't see anything obvious what should I be looking for.

mick1
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Fri Jul 06, 2018 6:29 am

Marks on the piston and cylinder walls.

If it's an Imola then a seizure would normally break the nicasil off the cylinder walls.........re-plating then required.

If your cylinder looks ok i'd be doubtful it was a heat seize. What was the symptoms ?

Jeff T
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Fri Jul 06, 2018 7:15 am

At first I thought I’d run out of petrol so same symptoms so switched to reserve but it just died then I couldn’t restart even after a couple of hours. When I checked there was still plenty petrol so it wasn't that. I’d been riding with a lad on a standard kit fairly slow only just on throttle when we got to a dual carriageway I opened it for 5 mins at the most and it was a hot morning but only about 10am so not like mid afternoon, waited for my mate then it packed in a couple of mins after I set off.

mick1
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Fri Jul 06, 2018 7:23 am

With a seizure your back wheel locks up.

Sounds like a fuel or electrical issue.

Is it running now ?

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