Ariel Square Four, Leader, Arrow & Twins / Singles Workshop Manual, 1937–1965 (OEM)

• Covers 1937–1965 Ariel Square Four 4G, Leader, Arrow, and various twin/single-cylinder models (including the 200cc Colt).
• Official Ariel factory publication, Sixth Edition by C.W. Waller (C. Arthur Pearson Limited), P/N: CAP-6.
• 84 exploded-view diagrams and detailed schematics for internal engine, transmission, and chassis assemblies.
• The definitive reference detailing the transition from early 4G push-rod engines to the later Leader and Arrow twins.
• Details complete tear-down and rebuild steps for the rocker box, Type GB gearbox, mainshaft bearings, kick-starter assembly, oil pump, and the foot-change operating mechanism.
• Outlines essential specifications and maintenance for the primary chaincase, timing chain, cylinder head, contact-breaker points, valves and seats, and the precise ignition timing on 500-c.c. engines.

Factory Service Details

This complete 119-page PDF manual delivers the exact maintenance and overhaul procedures used by original Ariel mechanics. Chapters trace the evolution of the 1,000cc 4G Square Four engines, specifically the Mk I and Mk II transitions, alongside the integration of S.U. Type M.C.2 carburetors. You will also find dedicated tear-down sections for the 250cc Leader and Arrow twins. Working on a single-cylinder? The guide covers the complete 200cc to 600cc lineup, including the NH, VH, and Red Hunter models.

Instead of paying premium rates at a classic motorcycle specialist, technicians and advanced DIYers can follow step-by-step instructions for tasks like setting the ignition timing on 500-c.c. engines, replacing mainshaft bearings, and completely dismantling the Type GB gearbox. Having this high-resolution document on your shop tablet allows you to pull up complex front fork schematics or Lucas electrical system diagrams (magnetos and dynamos) right at your workbench. It catalogs everything from rigid and plunger-type frame details to chain adjustments and wheel hub servicing. This direct access to factory tolerances prevents costly reassembly errors, providing serious time-saving value for your daily shop routine.

Technical Specifications & Component Visuals

Factory clearance settings and torque values ensure absolute precision during complete engine and transmission rebuilds. The manual indexes specific lubrication charts for both the 1,000cc fours and the smaller 250cc–650cc models. For example, technical data tables list the Square Four intake valve clearance at 0.003–0.004 inches, an oil sump capacity of 2.8 liters, and peak performance calibrated at 6,500 rpm.

The document includes comprehensive visual aids to expedite your workflow; alongside essential wiring diagrams, it features detailed engine cross-sections, precise valve timing charts, rocker box cutaway views, carburetor tuning graphs, and gearbox exploded drawings. These references make electrical and mechanical troubleshooting straightforward, helping you correctly identify part orientations and fix complex issues the first time.

When executing a repair on the Ariel Square Four, mechanics often encounter severe oil sludge buildup in the internal crankshaft galleries; failure to meticulously clean these sludge traps will restrict flow to the rear cylinders and cause catastrophic overheating. Additionally, on the single-cylinder models, undetected wear on the timing-side main bearing frequently causes sudden oil pressure drops that mask themselves as oil pump failures. Understanding these specific vintage traps is vital for any authentic repair and prevents irreversible damage to scarce engine casings.

Please note that vintage motorcycle systems require precise handling. Always verify your specific model year and ensure you use proper lifting equipment before beginning heavy frame or suspension work. This contents overview confirms what is inside the document; the actual download provides the comprehensive technical data and diagnostic schematics required for an accurate, reliable restoration.