12V 4.2KW 11T Starter Motor IS1105 for JCB construction equipment

Overview of the IS1105 Starter Motor

This IS1105 starter motor is the 12V, 4.2 kW replacement for JCB construction equipment applications. The housing, drive end and terminal positions follow the original design, so the unit bolts straight onto the bell housing and reuses the existing cabling.

Every unit is bench tested at the factory for current draw, solenoid pull-in and pinion throw, because those three values decide whether a starter works in a cold engine bay as well as it does on a test bench.

Technical Summary

• Rated voltage: 12V
• Rated output: 4.2 kW
• Pinion: 11 teeth
• Type: reduction gear starter with pre-engaged solenoid
• Application: JCB construction equipment
• Net weight: approximately 10 kg
• Condition: new, direct replacement for the original unit

A 12V 4.2 kW rating is the output the motor can hold while cranking, not a peak figure. It is sized so the engine reaches starting speed on the first or second revolution, which is what makes a healthy start feel immediate.

The reduction gearset lets the motor run at high speed while the pinion turns slowly with high torque, which is why the unit stays compact enough for a crowded engine bay.

Reference Numbers and Cross References

Cross references for this starter are listed below. They are a matching aid rather than a substitute for checking the number on the old unit:

• IS1105
• 11131292
• 11131697
• 320-09022
• 320-09346
• AZF4576
• AZF4181
• LRS02489
• AZF4301
• 11131711
• 11131848
• 11132113
• AZF4186
• AZF4224
• 6678205
• 28100-64040

Starter suppliers revised this design more than once during production. Confirm the number on the old unit, or send a photograph of the drive end, before committing to an order. This starter is listed with 16 references in total.

Where This Starter Is Used

JCB construction equipment applications in this range share the same mounting pattern and terminal layout, which is why one reference can serve several model years. Fitment is still decided by the starter number rather than by the badge on the vehicle. Because the IS1105 reuses the original bolts and connectors, no adapters are needed on JCB construction equipment.

If the number on the old unit falls outside the list above, send the engine code and a photograph of the drive end before ordering. A starter with the correct housing but the wrong pinion will grind on the first attempt and can chip the ring gear.

Failure Causes

Heat is the underlying cause in most cases. The starter sits close to the exhaust, and after a hot shutdown the solenoid winding and brush plate soak in heat with no airflow. Resin hardens, springs lose tension and the contact oxidises.

Most failures start at the solenoid contact. Each start switches the full cranking current through a copper disc, and after thousands of cycles that disc pits and burns. The result is the familiar single click with no rotation, or a delay before the motor turns. On JCB construction equipment installations, access to the IS1105 usually decides how long the job takes.

Symptoms of a Failing Starter

• No-crank with a fully charged battery
• Cranking that slows noticeably as the engine bay heats up
• Grinding that disappears on a second attempt
• Whine under load, suggesting a slipping pinion clutch
• Starter that continues to spin for a second after the engine fires

A cranking voltage test separates the starter from the rest of the circuit. If battery voltage stays healthy at the terminals but drops sharply at the starter stud, the cable or the connection is at fault rather than the motor. Owners of JCB construction equipment should treat the IS1105 reference list as a starting point, not the final answer.

Pre-Fit Checklist

• State of charge and age of the battery
• Corrosion on the earth strap and the engine-to-body bond
• Pinion tooth count against the ring gear
• Free movement of the new pinion before fitting
• That the signal wire connector seats fully on the solenoid

Most comebacks after a starter replacement trace back to something that was not checked before the unit went on: a tired battery, a corroded earth or a chipped ring gear. Ten minutes with a multimeter and a torch prevents the second repair.

Installation Procedure

With the battery isolated, remove any heat shield or ducting that blocks access and disconnect the main cable and solenoid connector. Support the unit before the mounting bolts come out; these starters are heavy enough to damage surrounding parts if they drop.

After fitting, confirm the pinion returns freely and the cables are clear of the exhaust. Crank once before the first drive, then re-check the main terminal for tightness after the first heat cycle. The IS1105 is built to the same flange pattern as the unit it replaces.

Quality Control and Supply from Hejian Nuojin Auto Parts Co., Ltd.

Each production batch is inspected for housing dimensions, terminal integrity and pinion fit, and every starter is bench tested before it is boxed. Units ship in neutral cartons with foam protection, which keeps freight damage low and allows distributors to label stock under their own brand.

Common references are kept in stock for fast dispatch, volume orders are delivered in around 30 days and each starter carries a one-year warranty against manufacturing defects.

Frequently Asked Questions

How do I confirm the starter matches my vehicle?

Compare the original part number first, then check the pinion tooth count and the terminal connector layout. The vehicle model alone is not enough, because more than one starter was fitted during production.

Why does the starter click but not turn?

A click with no rotation usually means the solenoid pulls in but the contact does not pass current. Check the earth strap and the main cable before condemning the starter.

Why does the starter work cold but fail when hot?

Heat raises solenoid resistance and reduces brush spring pressure. Both effects build up gradually and appear first on a hot restart.

Can the solenoid be replaced on its own?

It is possible, provided the motor draws normal current and the pinion is sound. Where the brushes are already short, replacing the complete starter avoids a second repair within a year.