Lambretta Overheating

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Jeff T
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Fri Jul 06, 2018 7:36 am

No stripped it down to check everything, don’t think it’s fuel I’ll check electrics.

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HxPaul
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Fri Jul 06, 2018 7:39 am

mick1 wrote:
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 ?
Not necessarily,with a soft seize it feels like you've just run out of petrol,as in Jeff T's case.If it were mine I'd get the top end off and inspect it,if all was well I'd be looking elsewhere.

Jeff T
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Mon Jul 09, 2018 8:29 pm

Bit of an update the flywheel key on the crank has sheared and the flywheel was loose, I have a Variatronic kit that's been on 12 months so bit surprised to see a key split like that.

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rosscla
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Mon Jul 09, 2018 10:12 pm

Make sure when you put it back together you take the time to lap the flywheel onto the taper of the crank with a bit of grinding paste.

The key isn't designed to stop the flywheel spinning on the taper. It's only there to ensure it goes on in the right place. The taper and the torque setting on the nut should be what holds it in place. If it sheared one of them wasn't right.
"Our dilemma is that we hate change and love it at the same time; what we really want is for things to remain the same but get better."

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ringwoodrob
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Sat Jul 14, 2018 7:35 pm

try using a different 2 stroke oil,rock oil injector2 4% when running in and 3% after stopped mine nipping up years ago,if the jettings correct,,,,,iron barrels get hotter they need the best with all this crapp fuel and crapp oil will break down and cause more friction hot hot lol

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ringwoodrob
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Sat Jul 14, 2018 7:38 pm

only read 1st page with that reply above lol

johnny650
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Sun Jul 22, 2018 10:07 am

hey MG are you still over heating ?
Something that occurred to me is that a lot of seizing can occur when the engine is under deceleration.......... Because under deceleration the throttle is shut off , the engine is still turning over at potentially high speed but is only supplied by the Pilot jet which is only supposed to supply sufficient fuel for idling. This results in a rapid rise in temperature of the engine which cannot be dissapated quickly enough hence the nipping up and seizing .

My suggestion is to up your pilot jet slightly from 45 to 48 so you have a richer idle mix and increase your idle speed setting slightly higher to give more fuel on deceleration.

You could also reduce the amount of oil in your fuel which would increase engine cooling.

Personally I always pull in the clutch and blip the throttle every few seconds if I am decelerating from speed after a sustained high speed run.

Another tip I read about recently that i didn't even think about before is to get your flywheel cowl as close to the fan blades as possible which apparently can have a dramatic effect on the amount of air drawn across the engine by the fan . ....You learn something interesting every day

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Doom Patrol
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Sun Jul 22, 2018 6:40 pm

Stator could be failing.

MightyGem
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Sat Aug 04, 2018 9:59 pm

OK, an update.

Took the scooter to my local Lambretta guy last November. There were marks on the piston and cylinder, from the nipping up, and carbon/oil sludge on the underside of the piston crown, but no obvious signs as to the cause of the problem.

It had done 8000 miles since it's restoration before it started overheating/seizing, although I'm thinking that the overheating was a result of it seizing. It would happen at a constant speed, around 45mph, on the flat, not under deceleration.

Anyway, I was persuaded to go for a stage 4 175 conversion and spent the winter/spring running it in.

Hopefully, the problem has gone away. Time will tell.

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LI150
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Sun Aug 05, 2018 4:13 am

Did your local Lambretta dealer tell you why he thought it had seized.

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