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Keihin Troubleshooting

Engine Cranks but Won’t Start

  • Out of gas
  • Incorrect starting procedure – when cold step on gas once, then crank.
  • Bad fuel pump – Remove fuel line from carburetor, place the open end into a jar or bucket and crank the engine. The correct way to test the fuel pump is with a pressure tester but start with just seeing if any gas is getting through.
  • Clogged fuel filter.
  • Engine flooded – Does is smell gassy. That would be a clue to flooding. Hold the throttle all the way to the floor and crank. Crank for 10 seconds then let it sit for 30 seconds holding the throttle down. Too much cranking will overheat the starter.
  • Bad Choke – When cold is the choke valve closed? When hot the choke valve should be open.
  • With the engine off look down the carburetor and pump the gas once. You should see a good squirt of gas. If not then either the carburetor doesn’t have gas, or the accelerator pump isn’t working.

Why Does My Engine Hesitate or Bog?

  • With engine off, look down the carburetor and pump the gas once. You should see a good stream of gas squirt into the bore. If not, then the accelerator pump circuit may be the problem. Assumes the float bowl is full of fuel.
  • Not enough fuel in the float bowl. Is the float level way off? Perhaps the fuel pump isn’t pumping enough pressure.
  • Dirty carburetor- take the top off and see if there is any dirt in the float bowl.
  • Bad fuel – too much water in the fuel, or especially dirty.
  • Clogged fuel filter or kinked fuel line.
Keihin Carburetor Kits

Why is My Engine Flooding?

Flooding is when too much gas is getting into the float bowl and running out the top vent, or maybe the throttle shaft. There will also be a strong smell of gas.

  • Number one cause of this is a dirty needle & seat. Try gently tapping around the inlet, or blowing compressed air into the inlet. This might dislodge any dirt. With the float needle closed blow into the inlet. Very little air should get through.
  • Fuel pump is over pressured. New pumps are especially suspect.
  • If the car has been sitting for months, the gas may have coated the inside of the carburetor with varnish. You will usually get a varnish smell. This would require a rebuild.
  • Float might be bad and filling with gas.
Get Keihin Carburetor Manual
Updated on 08/10/2021

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