How to Change the Coolant in a 1986 Suzuki RM250: MotoSport Guide

Shop parts for a 1986 Suzuki RM250 Dirt Bike.

Proper cooling system maintenance on your vintage 1986 Suzuki RM250 is key to peak performance – whether at the track or on the trails. Flushing and refilling the coolant is a straightforward procedure you can tackle at home with basic tools and a bit of care. This guide covers the full process and points out a few model-specific notes for your classic RM.

Preparation

  • Always work on a cold engine to avoid burns or pressure release mishaps.
  • Place the bike upright on a stand in a well-ventilated area. Gather basic hand tools, a drain pan, new coolant (preferably ready-to-use motorcycle coolant), a funnel, and if possible, a new drain bolt washer.

Coolant Draining

  • Remove the seat and side panels for easier access to the radiator cap if needed. Loosen and remove the radiator cap slowly to relieve any pressure.
  • Locate the coolant drain bolt at the base of the water pump on the right side of the engine. Position your drain pan beneath it.
  • Remove the drain bolt and washer, allowing coolant to empty fully. It helps to lean the bike slightly to the right to facilitate complete drainage.
  • For a deeper flush, briefly fill the radiator with distilled water and drain again to help remove old coolant and residue. Avoid using tap water due to mineral content.

Inspection & Installation

  • Check the drain bolt washer for wear and replace if necessary. This step helps prevent leaks on older RM250s.
  • Reinstall and torque the drain bolt appropriately. (On similar Suzuki models, this is around 8.0 lbf-ft or 11 N·m*.)

Refilling with Coolant

  • Using a funnel, pour fresh coolant up to the base of the radiator filler neck. The total system capacity is approximately 950 ml for comparable 250cc Suzukis*.
  • Gently rock the bike or squeeze the hoses to help release any air bubbles during filling. The RM250 does not have an air bleed bolt, so cycling coolant this way is important.
  • Replace the radiator cap securely.

Final Steps

  • Start the engine and let it idle until it warms up. Shut it off and let it cool fully, then recheck the coolant level – top off if necessary.
  • Check for leaks at the drain bolt and below the water pump.

Model-Specific Notes

  • The 1986 Suzuki RM250 uses a conventional, non-pressurized expansion tank setup. Inspect your radiator and cap for corrosion or damage that can affect sealing, which is common on older models.
  • Watch for signs of a failing water pump shaft seal (coolant in transmission oil, milky residue, or leaks below the water pump). Early intervention can protect your two-stroke's vital internals*.
  • If you notice repeated overheating, check for radiator fin damage or clogging, which can happen after years of mud, dirt, and the occasional crash.

Keeping your 1986 RM250's cooling system in top condition is essential for reliability & engine longevity. MotoSport stands ready with parts, maintenance products, and expert advice to keep your ride at its best.

<.-- *Descriptions of capacities and torque values reflect typical specs for similar Suzuki two-strokes of this era, but consult your service manual for exact figures and procedures. -->

Related Shopping Categories

Shop Radiators for a 1986 Suzuki RM250 Dirt Bike.

Shop Coolant for a 1986 Suzuki RM250 Dirt Bike.

Shop Temperature Sensors for a 1986 Suzuki RM250 Dirt Bike.

Shop Tools for a 1986 Suzuki RM250 Dirt Bike.

Shop Radiator Hoses for a 1986 Suzuki RM250 Dirt Bike.

Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.