Only runs "good" with the choke on

[C3Killer]

Ok, so I get the moped out of the shop the other day because the guy didn't have time to work on it. It was there for 3 months, and he didn't have time to work on it?!? Anyway, I start her up now with the choke on, and let her warm up some. With the choke on she runs fine. Kinda boggy for a few revvs and then WHAM, its like I hit NOS or something. Front end lifts, and heaven forbid I'm rounding a corner, I would loose it. When I am running for a couple miles, I take choke off, and shes soo boggy sounds like shes gonna die. Pull up choke, and I'm good. Whats this sound like?

AF18E motor, PG Long, 28mm oko carb,

[Bear45-70]

Improperly tuned carb.

[Wheelman-111]

Greetings:

Drop the carb, remove the bowl and have a look at the Pilot jet - the one that needs a small slotted screwdriver to remove. 2-3 months is enough evaporation time to gum up most of those little holes and produce the symptoms of a blocked Pilot circuit so beloved of stock carb owners. De-Gum that along with the Main and emulsion tube and she should be right. It only runs on the choke because that circuit alone is clear. However it won't run "right" on the choke either.

[C3Killer]

I'm not running a stock carb, 28mm oko.

[Bear45-70]

I'm not running a stock carb, 28mm oko.

It is still the place to start.

[C3Killer]

Ok, I'll do that, thanks.

[C3Killer]

Ok, I have taken the jets out and cleaned them out. I think I put it back together correctly. I am one clip up from center on the needle, and 1 3/4 turns out on the a/f screw. Still won't run without choke on, what direction do I go from here. Takes off like a bandit with choke on.

[Bear45-70]

The obvious is a vacuum leak.

[C3Killer]

obvious? What vac lines are there? I replaced the one from the gas tank to the intake. Here are some pics....

[C3Killer]

That "nipple on the bowl in the 4th picture.....what is that supposed to be connected to? The hose that was on it doesn't go anywhere., I thought may be it was the bowl "vent." Could this be the "leak" that is causing all my problems?

[Wheelman-111]

Greetings:

The bowl vents are not part of the intake stream. They're not likely your problem.
Lines can keep water out but aren't mandatory unless you ride in the rain a lot.

A Vacuum leak can develop between the carb and rubber spigot mount, the reed block,
crank seals or basically any gasket. Do check for cracks in the Vac line, too.

[C3Killer]

Ok, I just took off the carb, the mani, took out the reed block. Those all seal up good. I didn't know it had carbon fiber reeds. The vacuum line looks good, its brand new. Check check check.......whats the rubber spigot mount?

[Bear45-70]

You will never find a vacuum leak by disassembling the intake system. You need the engine running to find a vacuum leak. You really have no idea of what you are doing and you need to find a forum member close to you who can help. This way is gonna take forever.

[Wheelman-111]

Greetings:

The big black donut betwixt carb and manifold.
Hose clamps can cut the rubber. Overtightening can crease it.

How big is that Pilot jet? Did you swap pipes? Why was it in the shop for three months?

If it likes the choke, it must be too lean. Air leaks can cause this, but so can mismatched tuning.
The colder the ambient temps, the worse for a lean situation. Mine takes a while to warm up in 34 degrees.
I had to apply a little choke myself today for the first half-mile today. After that it ran fine.

[Trafficjamz]

What is your setup?

What cc engine, what pipe and what main/pilot jets are you using?

Sounds lean to me.