- A few things you need to look at when
trying to troubleshoot your
moped. How does it sound? If you run it wide open
when warmed up, does it peak out? or stutter? is it loud, or very quite?
- The symptoms can help decide what to try.
When you are going full throttle, the engine should get to a high RPM
sound smooth. Things that will make the engine sound or run different-
- Plugging air intake- will start well
cold, but be hard to warm up and not reach top speed. Engine will
at high RPM.
- Open air intake- to much air or air cleaner
is disconnected- engine will not have power at high speed, make vacuum
cleaner sound. Acts like it is running out of gas. ( sounds almost the
same as a dirty carburetor.)
- Plugged exhaust port- Engine sounds and
runs good, but has no power. Slow take off. Same as plugged muffler,
if the muffler is plugged you get a very smooth exhaust note at idle.
instead of pop pop pop pop
- Fouled spark plug- backfire. If you get
pretty good chance the plug is fouled.
- On models with
belts, the gear ratio drops as the belt gets thinner (most
hondas have belts).
- On a moped with
high mileage, the belt will cause slow top end speed if
you have a bike with chain
drive in oil bath (razz, suzuki FA 50, ) and you OVERFILL the oil
in the chaincase, that makes for slowww running as it requires too much power to turn the oil.
your engine does not rev up
well, and stutters or sputters, like when it is cold with the choke on,
the engine is running too rich. (too much fuel).
- Is the air filter
soaked with oil? Clean with soap and water!
- Is the air opening
in the airbox plugged? Very common for a spider or mud
wasp to build a nest in one of the intake holes .
- On a razz, it is
common to get a leaf stuck in the intake port of the airbox,
causing a 10mph drop in top speed.
- Don't try to
adjust the screws on the side of the carb to get lean or rich,
as they are for the idle circuit only.
- The idle airscrew
should be about 1 1/2 turns out on most bikes.
- Say your engine
revs but kind of wheezes, or acts like it runs out of gas?
- It is common to
have a buildup of hard scum on the inside diameter of the
hole in the main and pilot
jets, and it must be carefully removed.
- If your moped does
not idle the pilot jet is likely plugged.
- Anytime a moped
has not been
used for 1 year or more, and still has the same fuel in it, good chance
you will need to clean the jets.
- The poor
today's gasoline's have made this a rather steady bet.
- Mopeds are
affected more than
most vehicles because the small size hole the jet requires is
easily plugged, even by thick oily fuel, or water.
- Drain your carb
once in awhile! Most have a screw of
type at the bottom (where the drain needs to be) of the carb.
- Make sure the air
boot to the
airbox is not on wrong, kinked, hard and shrunken (QT 50)
- Don't oil the air
filter if you got the stutters.
- On a spree, you
can leave one snap loose on the airbox lid to allow it
to crack open, to get full rpm.
- But, beware, to
much lean out on the gas, and since the fuel cools the
piston, the piston can MELT.
- Still slow?
the muffler tip. Make sure no carbon buildup is inside the tip, stick
in as far as it will go.
- Common on razz to
have the tip bent over on a curb, then carbon up solid.
common on all types to have the whole muffler plug.
- When you have the
muffler off, is it heavy?
- Can you get the
baffle out to see if the holes are plugged?
- Check the exhaust
port on the cylinder.
- If you can't see
way in to the piston, use a mirror and a flashlight to make sure the
is ok and the port is not plugged where it meets the piston.
- Common on all
models to plug here, Just scrape it out so the hole is full
- Don't worry about
film on the inside of the port, I am talking about a very thin film
forms a wall in the exhaust port right next to the piston.
- A 1 1/2 inch hole
can be reduced to the size of a pea...... With a thin
film of carbon.
- If you can see the
piston ok, it's not the problem.
- If you are in
doubt regarding your
exhaust pipe being plugged, put your hand behind the muffler to see how
much pressure is expelled. compare to another bike.
- It should blow
pretty good, and have a distinct pop pop pop pop
sound while idling, not a steady hhhmmmmmmmmmmm.
If you are still struggling,
let me sell you something to make you feel
Scooter Therapy Inc
12 North Few
Street | Madison,
1-608-255-1587 | E-mail
12 N. Few
9-6 Saturday, 10-3 CST