Italika D150 Sputters and Dies - Please Help

[Nikibahama]

While I have an extensive background in Automotive maintenance/mechanics, I am new to scooters and know next to nothing about carburetors (other than them being a pain in the ass).

I have a D150 (150cc) Italika 4 stroke scooter. Months ago it began sputtering and dying. I'd go 100 feet and it would die. It would take forever to start again, go 500 feet and die, etc... I drained the gas tank, drained the fuel lines, replaced the fuel lines, replaced the fuel filter, blew out the carburetor with carb cleaner, re-assembled everything, filled with fresh gas and voila... she was back up and running like new. I hypothesized there must have been water in the gas somewhere, but here we are several months later and it's back to the same sputtering and dying garbage. I drained the gas, not a drop of water in it...


I drained gas from the drain tube that comes off the carb and hangs by the rear wheel. Once drained the moped started up and ran again for a few miles. Then it started sputtering again and I repeated... ran again for a couple miles. Every time I repeated this, it ran for less distance. Some guy passing by says "put it on the stand, it will start", so I put it on the rear stand (instead of kick stand) and it starts... No idea what the stupid stand has to do with anything, but thought I'd mention it. Put it back on the ground and it just turns and turns without starting (or starts after a minute of trying). So I put it back on the stand and it starts and begins sputtering. I disconnect the fuel feed line from the carburetor. Now it runs like a beast. Revs up, redlines, holds there, keeps going... runs for a minute straight without fuel connected. Re-connect the fuel line and the thing just sputters and dies. Spark plug is black so we're obviously running rich, but this is a stupid simple system... gravity drain fuel with a vacuum-controlled valve that then passes the gas through a filter and down to the carb. There is no fuel pump here where I could possibly be "pumping" too much fuel into this thing, nor have I made any adjustments to the carburetor (it's factory). Can someone please help me understand what the hell is going on here? I can rebuild an entire 8 cylinder motor in my garage but some stupid non-pumped, gravity fed factory carburetor with less than 1500 miles on it since new, is constantly giving problems and running rich without any excessive fuel pressure or force? I'm at my wits end with this stupid piece of s___.

[sc00ter]

Few things to try:

Try loosening the gas cap. You might be getting vapor lock.

Make sure the fuel line isn't being pinched somewhere.

If it has high miles or has been sitting for an extended amount of time you might have a clogged jet. I highly doubt that though.

The float height may need adjusting in the carb, or it could have gotten damaged. I've seen many people (including me) catch the float when pulling the float bowl off, knocking it out of adjustment.

Is the spark plug cap damaged or routed wrong, and/or pulling off the plug?

CDI failing. Also, highly doubt it.

Coil failing. Highly doubt it.

It does sound fuel related but it could also be:

Transmission issue. MANY variables....

Stator issue.

Bad earth ground, the ground can be in weird locations.

Nothing else is popping in my head right now.

I purposely picked a carburetor equipped scooter for the simplicity. I don't always like carbs but I've gotten pretty good at messing with them.

Keep us posted!

[sc00ter]

Oh, I've seen petcocks fail before but that is crazy rare. They work off a simple vacuum, on or off. You can pull a vacuum on the suction line (I use a shop vac) and see if the fuel flows and stops. The failure seems to be the little internal flap will warp and hang up. It's easier to replace it IF its bad. This problem rears its head on older scooters mostly. Again, very rare.

[sc00ter]

2 more things popped in my head last night:

Did you top off the fuel when filling it? Overfilling will flood the emissions system. I've done this twice on my scooter. Annoying but it will clear up after a few miles.

Plug gap set correctly? Usually the plug will be pre-set out of the box.

okay, 3 things. How many miles and has the valves been checked/set if needed to spec? That is the killer for most scooters, people not doing the valve checks. My exhaust valve will get a tad tight between check intervals