Difficulty starting. Ruling out the easy stuff first..

[Snails]

Cant get the scooter started. Its never been right/easy since I put a new engine in but it was running before the winter where I did some tinkering with the gearbox. Now it wont start. It sparks and gets fuel so I am a bit stumped. Before I get in to the hard stuff (electrics for me) I want to rule out the carb possibilities

I checked it over. I've even swapped out the main and pilot jets with spares. The starter jet is size 60 rather than the 50 I see recommended on the cambridge lambretta jetting guide. Would that make a difference. I cant seem to find any where selling different starter jet sizes so I guess people dont tend to change them anyway...its phbf 25 mm

[cgt75b]

Hi

Try a 45 pilot jet see if that helps the starting. Also if it's running through an air box take the bellows off the carb and see if it's any easier to start.

I am not saying this will solve your current problem but give it a bash, and see what happens.

Bloody scooters ehh pain in the arse at the best of times : )

The very best of luck with it.

Cgt75b............................

[Snails]

Thanks cgt. I have tried removing the air filter and fitting 45 pilot no luck

[cgt75b]

Have you tried bump starting it? Only recommended if you know what you are doing, you also need a fair lung capacity to use this technique.

[EddieStone]

Easy stuff first: Fit a new plug correctly gapped.
Check the timing - strobe is the best way, with the flywheel powered by a drill.
Check the choke is opening
Check you have compression/no leaks.

I had a poor starting problem with mine which was resolved by making the jetting richer, not leaner. That was after a rebuild though, with a modified kit and a different carb.

In my experience, carbs don't really mess up unless something drastic happens. You could check for blocked jets I suppose, the starter jet in this case. If the plug is wet, then your problems are probably elsewhere.
Poor starting is indicative of a knackered seal.

[Snails]

Have you tried bump starting it? Only recommended if you know what you are doing, you also need a fair lung capacity to use this technique.

No i have not. I do know what I'm doing as had a fair amount of experience doing this as a kid.

The reasons why not:

1. It does not even sound like it wants to start
2. Its quite hard work now-a-days
3. Pride

[Snails]

Easy stuff first: Fit a new plug correctly gapped.
Check the timing - strobe is the best way, with the flywheel powered by a drill.
Check the choke is opening
Check you have compression/no leaks.

I had a poor starting problem with mine which was resolved by making the jetting richer, not leaner. That was after a rebuild though, with a modified kit and a different carb.

In my experience, carbs don't really mess up unless something drastic happens. You could check for blocked jets I suppose, the starter jet in this case. If the plug is wet, then your problems are probably elsewhere.
Poor starting is indicative of a knackered seal.

tried a different plug but will check gap as forgot that when I did it
I've strobe tested it when it was running. Its on my list of tests but as Ive done it already and the scoot has not driven anywhere since I dont see why it should not still be correct - but I will double check if I run out of other ideas
Checked the choke is opening
Comparison seems fine on the kickstart shaft. I dont have gear for compression testing properly. I air tested the engine before I installed it, I've not done so since it started not wanting to start. Again its probably something I might do again if I cant do anything else like the strobing.

[Chris in Margate]

Buy a can of Bradex Easy Start from Halfords or similar.
Open throttle and spray generous amount into the carb mouth.
If it doesn't fire or start after 3-4 kicks, then it's not a fuelling issue. If it starts you can discount the electrics. Easy Start will normally start anything.

Compression tester should be used to see if you have at least 100 psi. £10 delivered from ebay.

Air leak derector using bicycle inner tube cut in half and either end secured at inlet and exhaust pipe and then pumped up.

[Snails]

Thanks Chris I like the logic of easy start.
Might invest in the compression tester as useful for tuning an stuff - in which I like to dabble

Ive got my home made air leak tester. Its great.

[Snails]

as useful for tuning an stuff

Actually thats total claptrap aint it. Thinking of measuring the cylinder head capacity which it wont do. Never mind, I'm sure it will be useful on lots of occasions.