Thermostat for Honda Pioneer, Rancher, Foreman and Rincon
Honda SXS 500 and 700 Pioneer, TRX 420 Rancher, TRX 500 Fourtrax Foreman, TRX 650 and 680 Rincon, 2003-2019
This is a brand new aftermarket thermostat, built as a direct replacement for the original unit fitted to the Honda SXS 500 and SXS 700 Pioneer side-by-sides and to the TRX 420 Rancher, TRX 500 Fourtrax Foreman and TRX 650 and TRX 680 Rincon quads built between 2003 and 2019. It replaces OEM part numbers 19300-HN8-003 and 19300-HN8-305. It is plug-and-play, a direct fit, and easy to install.
The thermostat is the valve that controls coolant flow between the engine and the radiator. While the engine is cold it stays shut so the engine reaches operating temperature quickly; once up to temperature it opens and lets coolant circulate through the radiator. A thermostat stuck shut causes overheating, and one stuck open leaves the engine running cold, hurting fuel consumption and, on a machine worked hard in cold or wet conditions, engine longevity. Every unit is tested before it is shipped. Our part number for this thermostat is RMS150-105805.
Key Features
- Brand new aftermarket thermostat, not a refurbished unit
- Direct replacement for the original Honda unit
- Cross references OEM 19300-HN8-003 and 19300-HN8-305
- Plug-and-play, direct fit, easy installation
- 50 mm diameter, 52 mm high
- Covers Pioneer, Rancher, Fourtrax Foreman and Rincon models
- All products shipped are tested
Technical Specs
| Specification |
Detail |
| Part number |
RMS150-105805 |
| Component type |
Thermostat |
| Diameter |
50 mm |
| Height |
52 mm |
| Fitment type |
Direct replacement, plug-and-play |
Vehicle Fitment Guide
Years shown are the overall coverage span for this part. Please confirm against the OEM part number on your original unit before ordering.
| Make & Model |
Years |
| Honda SXS 500 Pioneer |
2003-2019 |
| Honda SXS 700 Pioneer |
2003-2019 |
| Honda TRX 420 Rancher |
2003-2019 |
| Honda TRX 500 Fourtrax Foreman |
2003-2019 |
| Honda TRX 650 Rincon |
2003-2019 |
| Honda TRX 680 Rincon |
2003-2019 |
OEM Part Number Cross Reference
Aftermarket replacement. OEM part numbers are listed for reference only.
| Part Number |
Manufacturer / Brand |
| 19300-HN8-003 |
Honda |
| 19300-HN8-305 |
Honda |
Frequently Asked Questions
Will this thermostat fit without modification?
Yes. It is a direct replacement for the original unit on the models listed above, described by the manufacturer as plug-and-play, direct fit and easy to install. It drops into the original housing, so no machining or adaptors are needed.
What is included?
The thermostat itself. Gaskets, seals and coolant are not supplied, so have a fresh housing seal and enough coolant to refill and bleed the system ready before you start.
How can I tell that my old thermostat has failed?
A thermostat stuck closed shows itself as rapid overheating with a hot engine and a radiator that stays cool, because no coolant is reaching it. A thermostat stuck open does the opposite: the temperature gauge is slow to rise and never settles at its normal reading, and the fan rarely cuts in. Either way, the usual bench test is to drop the old unit in a pan of heating water and watch whether the valve opens and closes cleanly.
How do I check this is the right size for my machine?
Compare the OEM number on your original unit or its housing against 19300-HN8-003 and 19300-HN8-305. If no number is legible, measure instead: this thermostat is 50 mm in diameter and 52 mm tall.
Dispatched from the UK · 12-month warranty · Fitment support from our technical team
