Winter Fuel; Care And Cleaning; Troubleshooting - Demon 625 Street Carburetor 1900 Instruction Manual

Different fuels are used in the United States in the summer and winter. These fuels can even differ depending on what
part of the country you are in. Winter fuels have a higher Reid Vapor Pressure than summer fuels. In other words, the fuel
boils at a lower temperature than that of a summer blend. Most of the time this does not cause issues with drivability,
however in early fall or late spring when summer temperatures may still be present and winter fuels are in use it may
cause drivability issues. The most common problem observed is the fuel boiling in the fuel bowl and percolating out of the
vent tubes after the engine is shut down after a drive. Another less common issue is the fuel evaporating in the fuel line or
also known as vapor lock. The best thing that can be done if this is experienced is to isolate the fuel lines and carburetor
from excess heat by using a phenolic spacer under the carburetor and insulating the fuel lines. If you store your vehicle
over the winter it is highly advised that a fuel stabilizer such as STA-BIL is added prior to storing.
Street Demon™ carburetors do not require extensive maintenance. They are made from aluminum so over time the shiny
appearance can dull. Any quality aluminum cleaner and polish can be used to bring the shine back to as new condition.
Always clean the part first with a mild soap and water or non-vinegar based window cleaner, then polish as instructed by
the polish manufacturer. Always use a new microfiber cloth for polishing or unwanted scratches can occur. The composite
fuel bowl on the part #1901 Street Demon™ does not require any type of polishing; cleaning with a mild soap and water
will bring it back to new condition.
PROBLEM CONDITION
Engine cranks but
will not start
Engine starts, then
dies within a few
Cold Starting
seconds.
Engine normally
starts OK but then
dies backing out
driveway or at first
stop sign. After that
it runs OK.
Engine starts OK,
increases RPM
then gets too slow
with lots of black
smoke.

Winter Fuel

Care and Cleaning

Troubleshooting

POSSIBLE CAUSE
1) Choke not closing.
2) Choke linkage binding.
3) No gas in carb.
4) Accelerator pump defective or
worn out.
5) No spark or engine problems
such as bad compression.
1) Choke not closing properly.
2) Big vacuum leak on engine
somewhere.
3) Fast idle RPM set too slow.
4) Low fuel delivery.
5) Electrical or compression
problems on the engine.
6) Float level set very low.
1) Choke setting too lean
1) Choke set too rich
2) Slow flooding.
3) Float level very high.
16
CORRECTION
1) Inspect choke adjustment and for something binding. Adjust,
if necessary.
2) Lube with WD-40 and check for something bent. Adjust if
necessary.
3) Check fuel delivery. Look for plugged filter or clogged lines,
bad pump, stuck needle & seat, and fuel pressure.
4) Replace the pump. Problem is usually caused by bad gas,
dirt in gas, or vacuum leak or ignition problems.
5) Diagnose & correct the problem.
1) See notes above. Adjust choke if necessary.
2) Use vacuum gauge to check. Fix the leak. You may have put
the base gasket on wrong or it is the wrong one for this carb &
engine combination.
3) Adjust to recommended RPM.
4) Correct delivery to carb. Usually it is a plugged up filter.
5) Do complete tune up & diagnosis. Fix the problem.
6) Set to factory specs. Factory setting, with air horn upside
down, is 1.01"+/- .015" from the cast surface to bottom of float.
1) Richen choke by adjusting cap counter-clockwise
1) Lean choke by adjusting cap clockwise
2) Fix cause of flooding.
3) (Rare) Set to factory specs - Factory setting, with air horn
upside down, is 1.01"+/- .015" from the cast surface to bottom of
float.