Modern Vespa

vespa wont start new gaskets on carb new gaskets on piston new spark plug new petrol ???? any ideas

Make sure the spark plug is screwed all the way in.

cheers but tryed the spark plugs but had cheap oil in mix before emptying tank and had blck oil on spark plug so changed it 3 times left it alone for a week and it kicked over and ran for a spin of about 5 miles parked it up for the night and next day ,no start again ???

Exactly what model Vespa is it, and what reg. year?

Ok its a lml frame 1999 and a one year old mallossi 166cc engine running ok untill got short of petrol and put in c, heap oil then had p, troblems so drained tank and now wont start even with new gaskets car.b checked new spark plugs ect

First thing I look for besides kill switch.

OK, suspected something of the sort - so moved to the 'Not so Modern' section where you will hopefully find an expert or twenty.

with the fuel tap on, if you unscrew the banjo from the carb, just a little, maybe an eighth or quarter turn, does fuel come out? If you remove the spark plug and ground it against the head, do you have spark? What's the compression read? I've got a bike that gets about 90psi which is bottom of the chart, and is a bitch to start.

Got good spark as jolted arm a cou
ple of times carb clean and seems to be ok some onementioned thebad oil sitting in the sump andto empty the sump but dont know how to empty sump ,

if any one is out there just sent all day stripping the engine down and cleaning evey thing and got the scoot started at last BUT now have petrol coming out off carb manafold so checked fuel line but ok so another job another day ? at least its running.

By carb manifold, do you mean air box? I would guess you need a new needle for the carb float. If it runs, does it run really rich or stall after a while? is your plug really dark? Rule I've set for myself, is always keep a carb rebuild kit on hand. When you use one, buy one. When you need one, buy two.

cheers for the tip gaskets for the carb x2 are on order even though i changed them three weeks ago will change again and use gasket sealer this time to be sure.

Needle, you need the needle.

This definitely has nothing to do with gaskets.

Sounds like you need a new float needle(as mentioned) and a good carb adjustment.

Try turning the fuel tap off and let it sit for a while to let the excess fuel evaporate. Then turn on the tap and try again. My guess is it will start.

If it does you can be pretty sure your float needle is worn.

Weii its been 6 weeks now and im still scratching my head ????? Ive changed the needle and float and gaskets in the carb ? TOTAL WASTE OF TIME .... changed the base and top gaskets on the piston and then paid out for a new exhust and still the scooter will kick over on the first kick every time and will tick over steady BUT as soon as i drive it up the road it cuts out. and NO its not the petrol as ive changed that as well and cleaned the tank out and put in a new fuel line ???? so any ideas any one as im at the end nearly ????????

When it stops, how long before it will start again? 5 minutes? A day?

Have you checked the fuel tank lid is clear and able to breathe?

When it stops and you pull out the plug, is it wet or dry?

Hi Ginch it takes about 10 - 15 mins before it will start again and the plug is wet ???

Also tried to run it with no petrol cap on in case it was the breathing hole in cap but did the same and cut out .

loose spark pug cap...??

you do the fuel flow test yet...??
you rebuild the gas tap yet...??

What jets are you running in this carb? Do you use the choke to start it? If so, how long is the choke on for?

As Spider says it may be electrical as well.

choke rarly needed starts fist kick normally and wiring been tested but seems all ok carb set up via mallossi with engine two years ago.

usually if a cold engine does not need the choke at all then the idle jet / mixture screw is set up too rich

or

it is not closing all the way which leads to a richer than needed jetting / plug fouling issues

^^^^^^^ That, especially plug wet or dry.

Remove the carb box top and air filter, take a small amount of extra fuel with you, then ride until it quits. Pour about a half shot glass of fuel directly into the carb and see if it starts and runs. Things can happen that interfere with carb fuel delivery even after doing what you've done. Using your emphatic NO up there has gotten me into trouble many times.

Something like this will let you see if spark is happening, or pull the plug, hold it against metal and look for a spark.

http://www.amazon.com/Fool-proof-Engine-Ignition-Spark-Tester/dp/B0042KJV9U

That ad is slightly untruthful about foolproof since a plug can pass ignition current without a spark actually occurring.

Look in the tips and tricks (Voodoo post) thread for a homemade spark tester.

Good idea Blackbart... here's the link to the tester. I've used and recommended this so many times I should be giving Voodoo royalties!
https://modernvespa.com/forum/post1548781#1548781

Cheers lads . some great tip and sites had it going today and drove it for half a hour before it cut out so tried the petrol in the carb . Sorry no help it just did not start. The only thing that i havent changed is the CDI unit . is there a way of testing these as i have spark .

How do you know that you have spark when it stops? What method did you use?

Also, next time pull out the spark plug when it stops and note whether it's wet or dry. A photo might help us too. You haven't told us what jets you are running as yet.

Well finally cured the problem I replaced the cdi unit forr the second time and wham all ok again so at last ready for the isle of white rally so see you all there .