Jet Keihin Pilot #38 (FCR-MX) (4/Pkt)

The Keihin Pilot Jet #38 is a direct-fit replacement slow jet for Keihin FCR-MX flat-slide carburettors, sold in a pack of four. Pilot jets govern fuel delivery at closed to quarter-throttle openings, making them the primary tuning lever for idle quality, low-speed response and choke-off cold starting.

Suited to motocross, enduro and off-road riders who are re-jetting for altitude, temperature changes or engine modifications, this pack provides multiple jets so you can work through a jetting sequence without waiting on individual orders.

• Size #38 pilot jet sized for Keihin FCR-MX flat-slide carburettors
• Controls fuel delivery from closed throttle to approximately quarter throttle
• Pack of 4 jets — sufficient for a full jetting sequence without reordering
• Direct OEM Keihin replacement part
• Precise orifice sizing for consistent, repeatable jetting results

• 4 x Keihin Pilot Jet #38 (FCR-MX)

Remove the carburettor float bowl to access the pilot jet; use a correctly sized flat-blade screwdriver — an ill-fitting tip will damage the jet's brass slot.
Thread the jet in by hand first to avoid cross-threading the aluminium carburettor body, then snug lightly; do not overtighten.
Blow compressed air through a removed jet to clear blockages; never use wire or a drill bit, as enlarging the orifice even slightly changes the jetting characteristic permanently.
If idle quality or low-speed response degrades after cleaning, inspect the jet orifice under good light for wear or debris before replacing.
When tuning for altitude or temperature, move one jet size at a time and test between changes — the #38 is one step in a range, and a rich or lean condition at idle is often resolved with a single size change.
Store unused jets in a sealed container away from moisture; corrosion inside the orifice will alter flow and introduce inconsistent running.
Always re-check and re-set idle mixture screw position after changing pilot jet size, as the two are interdependent.