MOPED ARMY

When I first got it this is actually what I did before I bought the foam element, and it was actually much worse (noticeable deceleration when I opened the throttle all the way). This was before I got the new carburetor and cleaned the exhaust, though, should I try it again? I could try a cone filter too.

I may also try running it without the exhaust pipe to rule that out but I don't want my neighbors to hate me. (edited)

I will try those suggestions. Now that I have two carburetors I'm a little less skittish about ruining one ;)

I'll try running with the choke on but if everything is stock I shouldn't need to rejet though, right? I worry if I rejet I might just be band-aiding some other issue, like an air leak... Admittedly, I reused the old gasket for the new carburetor.

I'll get back in a few hours but still open to suggestions so I can try 'em all at once. Thanks! (edited)

New carb is probably overjetted. When you said you CHANGED the spark plug,was it a new one?

Whenever I have suffered 4-stroking it was always over-jetted or a restrictive airbox.

I’m going to clean the old carb and put it back tomorrow cuz I got the day off but I also noticed the carb leaks a bit of fuel out the overflow at the bottom, would this be an indication it’s running rich or some other problem, or is it normal? It doesn’t seem like a lot, it is barely enough to wet the surfaces the overflow tube is resting on, and make my finger wet if I touch the end of the tube. I can get pictures in the morning for a better visual.

How many times did you press the primer button without starting it?

I don’t have a primer button. There’s a prime lever on the fuelcock but I only had to use that when I first replaced the carburetor.

An FA50 uses an automatic fuel valve ( petcock ) .

Unless something is not right or it has been replaced with a different style , anytime the motor is not running or being turned over , fuel will not pass until it is switched to the prime position .

If the carb is leaking out of the drain at the bottom of the bowl : the float may be stuck ; the float valve may be dirty ; the drain screw might need attention or the brass over flow tube could be cracked .

In stock configuration , the FA50 runs best with a OEM type foam air filter set up and the carb adjusted per the manual , exactly .

My FA50 started first kick , most often , and held 30+MPH for as long as I cared to ride , when it was totally stock .

Now , technically , it isn't completely stock : less 1 ring and the piston crown has been 'channeled' which lowered the compression a bit slightly quickened transfer and exhaust flow . The carb has been adjusted to accommodate the changes and the bike does as much as 34 - 35 MPH . The piston and rings are due for replacement as both have about 8,000 miles of pretty hard riding .

I guess I’ll have to anyway if it’s gonna keep overflowing

Slide adjustment is best accomplished via the adjusting ferule atop the carb .

So I put the old carburetor back after what I think was a good cleaning, and it stopped bogging at full throttle but still only went 25. I noticed an air leak (detected with starting fluid; engine died when I applied it to the intake manifold) which applying some Permatex seemed to fix. Any issues with top speed should be with the engine itself at this point, right?

Good idea. I don't know why China makes such bad products and not just moped parts.

I see. The manual makes a great deal out of cleaning carbon from the combustion chamber and exhaust port as part of the maintenance procedure, and I've already put my stock carburetor and air filter on, as well as fixed any air leaks. It runs consistently at full throttle, but just barely breaks 25 mph. Judging by the amount of carbon I found in the exhaust port while cleaning the pipe, there's probably still a fair amount in the combustion chamber.

So I suppose my next step will be a thorough inspection of the engine and transmission. Maybe a compression test as well? How many kicks will give an accurate reading? Just once? And lastly, the manual only gives a compression ratio of 6.5:1. How does this translate to PSI? (edited)

6.5:1 CR

average sea level atmospheric pressure = 14.7psi

6.5 * 14.7psi = 95.55 psig (on a gauge).

if you're at any kind of altitude, you have to take that into account (which is what the paragraph from PD explained).