Home / Repair / Motorcycle/Car losing power randomly, but idle is perfect.

Motorcycle/Car losing power randomly, but idle is perfect.

Most likely reason - Since the engine is idling fine even when there is no power, issue is with the electrical system.

Is your motorcycle losing power, but engine idle is fine?

Is scooter / bike stalling randomly but engine turns on and run perfect at beginning?

Popping sound from engine when accelerating and losing power?

Engine RPM not increasing when accelerating?

Most likely reason - Since the engine is idling fine even when there is no power, issue is with the electrical system.

Usually happens when a part of electrical system in the vehicle is almost failed but not fully.

But we will also look at other issues like mechanical or vacuum issues also.

Popping sound can happen when fuel air mixture is too lean or too rich.

This can happen because of many reasons. But idle is fine, we are focusing mainly on electrical issues.

Other Symptoms — Engine bogging randomly, but idle fine.

  • Engine idle fine but no power.
  • Starts & idle fine but bogging.
  • Popping sound from engine.
  • popping sound from exhaust.
  • Scooter bogging when accelerating.
  • Scooter/car losing power while riding.
  • Scooter stalling when accelerating
  • Scooter losing power when accelerating
  • Scooter stops randomly, but idle is fine.

Reasons of losing power but engine idle perfect.

  • Faulty Spark plug - spark plug is one of the parts that need regular replacement. All symptoms listed above can happen because of a bad spark plug.

Spark plug

  • Ignition coil - a failing ignition coil or one with wrong specification will cause this issue.

Ignition coil

  • Battery - Very low chance of this issue happening because of battery. But it should be on the checklist.

  • Magnetic coil / Pickup coil — if one or two winded coils is getting faulty, this issue will happen.

  • CDI Unit — a failing CDI unit will be the result of many issues starting from low fuel efficiency to engine stalling, scooter stopping after getting hot etc.

  • Carburetor main jet clogged - there is low chance of this being the problem. But since the vehicle idle is perfect and the issue happens when accelerating, technically this can be a reason too. If the popping sound is coming from the exhaust, there is more chance of a clogged main jet.

  • Spark plug cap not tight — a loose spark plug cap will cause all the problems mentioned.

  • Vacuum petcock valve - Since engine runs fine for intermittently or randomly, petcock valve should also be in the suspect list.

  • vacuum leak - vacuum leak can cause many issues, starting from engine bogging to randomly stopping.

  • Clogged fuel tube - very low chance, but a very old and leaking tube should be replaced as a precaution.

  • Air filter clogged - again, very low chance of this problem happening because of air filter. But should be checked.

  • Empty engine oil - Yes, this can happen because of leaks and is one of the primary checks you have to do.

  • Fuel tank cap clogged — fuel tank cap have a very small hole as an air went to allow flow of petrol. If this is closed, fuel will stop going to the carburetor because of air sealing itself.


  • Step 1 — inspect /clean & adjust gap or replace spark plug.

  • Step 2 - Carburetor main jet clogged - clean carburetor.

  • Step 3 — Battery — check voltage.

  • Step 4 — Ignition coil — check voltage. If faulty, replace.

  • Step 5 — CDI Unit- check voltage from the pickup coil to the CDI. If faulty, this should be replaced.

  • Step 6 — Magnetic coil / Pickup coil — open and check for any rust / burned coil.

  • Step 7 — Spark plug cap not tight — Make sure cap is fitted tightly by pushing it.

  • Step 8 — Vacuum petcock valve - suck in air via tube that goes to the vacuum source(usually engine head) and make sure that fuel is flowing from petcock to carburetor.

  • Step 9 — vacuum leak - start the vehicle. Then spray soapy water on tubes and check for any vacuum leak.

  • Step 10 — Clogged fuel tube - replace all tubes to make sure there is no clogged/leaking tubes.

  • Step 11 — Air filter clogged - open air filter compartment. Inspect and clean/replace air filter.

  • Step 12 — Empty engine oil - check engine oil level and replace add oil if necessary.

  • Step 13 — Fuel tank cap clogged — open, inspect and clean fuel tank cap.

Written on October 6, 2021
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Engine idle fine but no power Starts & idle fine but bogging Popping sound from engine popping sound from exhaust Scooter bogging when accelerating Scooter/car losing power while riding Scooter stalling when accelerating Scooter losing power when accelerating Scooter stops randomly, but idle is fine


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