How to Repair the Ignition System on a Yamaha PW50

Written by brianna byrne
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How to Repair the Ignition System on a Yamaha PW50
Yamaha recommends that owners only try to repair the PW50 ignition system's spark plug. (Stockbyte/Stockbyte/Getty Images)

A small dirt bike designed for younger riders, the PW50 features a compact frame and a 49cc engine. Despite its size, the PW50 is susceptible to the same periodic mechanical failures or problems as all vehicles, requiring occasional repairs. Yamaha suggests that owners attempt some minor replacement and adjustment of the spark plug to repair a faulty ignition system. The company does not recommend that owners attempt any major repairs of the ignition system.

Skill level:
Moderate

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Things you need

  • Spark plug wrench
  • Spark plug gap tool
  • NGK BP4HS or a DENSO W14FPL replacement spark plug
  • Wire thickness gauge

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Instructions

  1. 1

    Locate the spark plug, which is situated within the PW50 engine's single cylinder.

  2. 2

    Remove the spark plug cap covering the plug. Then twist the spark plug away from the cylinder with a spark plug wrench.

  3. 3

    Inspect the condition of the porcelain insulator tip. This tip should be medium to light brown in colour. If it is burnt, cracked, or brittle, owners must replace it. The Yamaha PW50 takes an NGK BP4HS or a DENSO W14FPL plug.

  4. 4

    Measure the spark plug gap using a wire thickness gauge. The spark plug gap is the distance between the spark plug and the hook at one end of the plug. For the PW50's spark plug to work properly, this gap should measure between 0.024 and 0.028 inches.

  5. 5

    Widen the spark plug gap as needed using a spark plug gap tool to gently pull the hook outward.

  6. 6

    Shorten the spark plug gap by pressing the hook against a solid, flat surface.

  7. 7

    Reinstall the spark plug with the spark plug wrench and return the spark plug cap.

  8. 8

    Try the starter again. If ignition system still does not work, take the PW50 to the shop.

Tips and warnings

  • Yamaha urges owners to take the PW50 to a certified dealer for repairs if the ignition system experiences major mechanical failure.
  • Use only NGK BP4HS or a DENSO W14FPL spark plugs in the PW50. Any other kind of plug can cause serious engine damage.

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