TBParts Big Valve Kit – Honda Grom, Monkey & MSX 125 (2021 & Older)

TBParts Big Valve Kit – Honda Grom, Monkey & MSX 125 (2021 & Older)

Maximize airflow and unlock more power from your Honda Grom, Monkey 125, or MSX 125 with the TBParts Big Valve Kit. Featuring a +1.5mm oversized intake valve and a +0.5mm oversized exhaust valve, this kit is engineered to outperform the factory valves in every measurable way — more flow, more strength, and less weight.

Both valves are machined from EV8 stainless steel, a premium alloy that delivers superior heat resistance and longevity over OEM valves. The redesigned valve profiles improve flow characteristics for real-world power gains, while the lighter construction reduces valve float — allowing the engine to rev higher and faster while freeing up horsepower previously spent moving heavier stock valves.

Features

• +1.5mm oversized intake valve for increased airflow and power
• +0.5mm oversized exhaust valve for improved scavenging
• EV8 stainless steel construction — stronger and longer-lasting than OEM
• Lighter than factory valves — reduces valve float and frees up horsepower
• Redesigned valve profiles for superior flow characteristics
• Direct upgrade for stock cylinder head (valve seat cutting required)

Fitment

• Make: Honda
• Models: Grom 125 (MSX125), Monkey 125
• Years: 2021 and older only

Part Number

• TBParts PN: TBW1042

Installation Note

This kit requires professional installation by a qualified mechanic or machine shop. Valve seats must be cut to accept the larger valve head diameters, and valves must be sunk to the correct depth to maintain proper overlap clearances. Refer to the TBParts installation spec sheets for protrusion and install height specifications before beginning work.