Kioti NX-series transmission solenoid recall — loss of reverse on HST models

## Affected machines All four Kioti NX-series compact tractors with HST (hydrostatic) transmission, regardless of cab configuration: - **NX4510** / NX4510 HST / NX4510 CAB / NX4510H CAB - **NX5010** / NX5010 HST / NX5010 CAB / NX5010H CAB - **NX5510** / NX5510 HST / NX5510 CAB / NX5510H CAB - **NX6010H** / NX6010H CAB Year range: 2014 onward. The campaign covers the full production run because the affected solenoid supplier was in use for an unspecified window before Kioti switched suppliers. There is no published serial-number cutoff in any source we located; if you have an NX-series tractor of any model year with the symptoms below, contact your dealer. Note: Synchro-shuttle (gear) NX models without the electronically-controlled HST are not affected by this specific solenoid issue. ## Issue The NX series uses an electronically-controlled hydrostatic transmission that is unique within the Kioti lineup (the similarly-sized NS series uses a different transmission). One of the small solenoids in the HST control circuit was sourced from a supplier whose parts had a quality problem. Per a dealer/technician account on TractorForum: > "It's a known issue. It's a small solenoid that Kioti had an issue with a run of them, fired that supplier, and went with another. It affected multiple NX models." Symptoms reported by owners: - **Loss of reverse**: tractor will not move in reverse, or moves only intermittently. Restarting the tractor sometimes restores reverse temporarily. - **Surging when HST is pushed forward**: the tractor accelerates in pulses rather than smoothly. - **Intermittent reverse engagement**: reverse "comes and goes at random" — works fine for a session, then fails on the next. The failure mode is electrical/hydraulic in nature, not mechanical wear, so it can manifest with very few hours on the tractor. One reported case: NX6010 bought new in May 2021, problems from the start; symptoms intermittent enough that two different dealers struggled to diagnose initially. ## What to do 1. If you observe any of the symptoms above on an NX-series tractor, contact your authorized Kioti dealer. The fix is covered under warranty. 2. Be prepared for a long shop visit. The solenoid is "in a horrible spot, mid tractor under the area of the seat" per the technician quote — the tractor must be split at the mid-frame to access it. This is not a 30-minute job. 3. Avoid attempting to "drive through" the symptoms. Loss of reverse on a loaded tractor (loader full, on a slope, in soft ground) creates real exposure: you may not be able to back out of a situation. 4. If your dealer is not familiar with this campaign, the Kioti Service Bulletin / warranty coding is internal and not published publicly, but the dealer's Kioti technical-support line can confirm the campaign exists for your machine. ## NX-specific operating notes (separate from the recall) The NX-series HST has some operating quirks that, while not part of the recall, can mimic or compound transmission issues: - **Do not press both HST pedals simultaneously** — this corrupts the HST calibration and can require recalibration at the dealer. - **Linked-pedal mode**: if your tractor has the linked-pedal feature and is shut down with that mode active (rather than in neutral), recalibration may be required on the next start. - **No-stall / speed-limit switch**: similar — wrong-state-at-shutdown can require recalibration. If your symptoms are limited to "tractor won't move at all on next start" rather than the loss-of-reverse / surging pattern above, the problem may be a calibration issue rather than the solenoid recall. Your dealer can determine which. ## Hazard Loss of reverse on a tractor performing loader work, snow removal, or any task that involves backing out of an obstacle is a real safety issue. Surging on forward HST input compounds this — operators have reported the tractor lurching unpredictably during loader work. Severity is rated **critical** for this reason, even though no published CPSC or NHTSA recall covers it. ## Source - TractorForum.com thread "Recall for Kioti NX series tractor", with multiple owner reports across NX5010 and NX6010 and an explicit dealer/technician confirmation of the campaign and root cause. - Kioti NX-series product literature confirming the four-model lineup (NX4510 / NX5010 / NX5510 / NX6010) and the electronically-controlled HST option. ## Library note The four NX-series tractor model rows are being added to equipment_models in the same migration as this bulletin (migration 050). Per the established standing rule: when bulletin research surfaces an issue on a model not yet in the library, the model is added in the same migration as the bulletin so the bulletin can attach immediately rather than requiring a separate backfill task.