Yamaha NMAX 155 - Master Maintenance & Torque Guide

Field note: The NMAX 155 Blue Core engine features an oil strainer screen (OEM # 2DP-E3411-00) and requires 0.9 L of 10W-40 JASO MB oil. Check final drive gear oil (150 ml refill volume) during every main service. For shared 155cc platform data, view our Yamaha SMAX 155 master guide. Learn more about variator nut spline protection in our CVT variator nut torque analysis post.

Field note: This element is an OEM exact fit with no tolerance for a "close enough" generic substitute — a slightly undersized aftermarket filter allows unfiltered air bypass around the edges, which is functionally worse than running with no filter cleaning at all since it goes unnoticed. Keep airbox screws at 1.5 Nm; the plastic mounting ears crack easily under power tools.

Field note: Weigh all six rollers individually before installation — a variance of even half a gram from the 13g spec is enough to produce a noticeable flat spot in acceleration on this displacement class. Torque the variator nut to 45 Nm on a clean, dry taper; skipping the cleaning step is the most common reason for premature nut loosening reported on this platform.

Field note: This Blue Core engine runs a wider 0.8-0.9mm gap than most small-bore competitors, and installing a plug pre-gapped to a more common 0.6-0.7mm scooter spec produces a measurably weaker spark event that can trigger intermittent misfire under load. Always verify the gap with a feeler gauge before installation rather than trusting a "pre-gapped" label.

Field note: On the Blue Core short block shared with the NVX 155, the piston pin circlips must be installed with the opening gap oriented 90° to piston travel, never fore-or-aft. A backward clip compresses under inertial load on every stroke until it walks out of its groove and ejects into the crankcase, and the freed pin gouges the cylinder wall on the following stroke, destroying the bore. Use only new clips and confirm full seating by feel before closing the case.

Field note: Yamaha's painted plastic panels become progressively brittle at the mounting tabs after roughly three years of continuous UV exposure. Never use an impact driver on body screws, and apply silicone grease (never petroleum-based) to rubber grommets before removal so panels flex free without cracking.