Flywheel Puller LH vs RH Thread: What is the Difference

Flywheel pullers come in right-hand (RH) and left-hand (LH) thread versions, and using the wrong one is a common - and expensive - mistake. This guide explains the difference, why both exist, and how to tell which one your motorcycle needs.

What RH and LH Threads Mean

• Right-hand (RH) thread - tightens when turned clockwise (when viewed from the top). This is the standard direction for most bolts, and for most flywheel pullers.
• Left-hand (LH) thread - tightens when turned counter-clockwise. Used on rotating parts where normal engine rotation would otherwise loosen the fastener.

Why Some Flywheels Use LH Threads

On some engines, the flywheel is on the left side and rotates in a direction that would unscrew a normal RH-threaded puller or retaining nut. To prevent self-loosening, manufacturers use a left-hand thread. This is especially common on:

• GY6 125cc and 150cc scooters (very common LH flywheel)
• Many two-stroke MX and dirt bikes
• Some Honda, Yamaha, Kawasaki and Suzuki models

How to Tell the Difference

Visual Check

Look at the thread angle. On a RH thread, the thread crests slope upward to the right. On a LH thread, they slope upward to the left. Place the part with the thread facing you and follow one thread crest - if it rises to the right, it is RH.

Try a Known Bolt

If you have a normal right-hand bolt of a similar size, try to engage it lightly. If it starts to thread, the flywheel is RH. If it will not start, it is likely LH.

Check the Service Manual

The service manual almost always states the flywheel puller thread direction and size.

What Happens If You Use the Wrong Direction

An RH puller forced onto an LH flywheel (or vice versa) will cross-thread and permanently damage the flywheel threads. The flywheel then cannot be removed properly and may need replacement. This is why confirming thread direction before ordering is essential.

NACHEE Flywheel Pullers - RH and LH in Stock

NACHEE manufactures both RH and LH flywheel pullers across the full size range (M14 to M50), including the common M27×1.0 LH for GY6 scooters and M28×1.0 RH for modern four-stroke MX bikes. Send us your bike model and we will confirm the correct thread direction.

Website: https://www.nachee.cn
Email: lilywang@nachee.cn
WhatsApp: +86 13611901566