Royal Enfield Chaincase Inner / Back Half (Inches, 4-Speed KS) – Pre-Mar 2002 | 111889

If your old Royal Enfield’s primary chaincase is leaking, cracked, rubbing the chain, or has damaged mounting points, replacing the chaincase inner / back half is the correct long-term fix—not sealant or welding. Part No. 111889 is the chaincase inner (inches type) used on 4-speed Kick Start (KS) Royal Enfield motorcycles manufactured before March 2002 (older “inches” hardware standard). 

This is the inner/back half (engine-side piece) that supports alignment of the primary chain run, keeps the chain protected from dust/water, and helps prevent oil seepage when paired with the correct gasket and fasteners. Unlike many generic aftermarket castings, a correct-spec replacement helps maintain proper clearances—reducing chain noise, premature wear, and repeat leaks.

Best practice: replace the gasket, inspect the primary chain/sprockets, and verify whether your bike uses inches vs metric chaincase hardware before ordering. (If your bike is later-model 5-speed / AVL / Electra / Thunderbird / Lightning, fitment must be verified—see compatibility.) 

Key Features 

• Genuine-spec Chaincase Inner / Back Half for Royal Enfield primary drive

• Part Number: 111889 (commonly referenced as chaincase inner/back half) 

• Designed for 4-speed Kick Start (KS) models before March 2002 

• “Inches type” chaincase variant (important for correct mounting/fasteners) 

• Helps restore proper primary-chain protection and reduces oil seepage risk (when installed with correct gasket)

• Direct replacement concept—no machining typically required (as per multiple dealers) 

• Ideal for restorations / rebuilds of older Bullets

• Recommended add-ons: chaincase gasket, correct fastener set, primary chain inspection

Compatibility Table (PLEASE CHECK PART NUMBER BEFORE PURCHASE)

Explicit caution 

Some sellers explicitly warn this part is not for Electra / Machismo / Lightning / Thunderbird families. Treat those as NOT compatible unless you verify by chassis + parts manual. 

Variants

• No variants (single part).
  If you want, you can add a Shopify note/selector for: “Inches (Pre-Mar 2002) vs Metric/5-Speed” to stop wrong orders.

FAQs 

1. Is 111889 the inner or outer chaincase?
   It is commonly sold as the chaincase inner / back half (engine-side half). 

2. Will this fit my 5-speed / AVL / Electra / Thunderbird / Lightning?
   Do not assume. Several sellers state it’s for 4-speed KS pre-Mar 2002 and caution against Electra/Thunderbird/Lightning families. Verify by your parts manual/chassis. 

3. What does “Inches type” mean?
   Older Bullets used “inches” hardware standards; the official retired catalogue lists 111889 as chain case inner (inches) and notes before Mar 2002. 

4. What should I replace along with this?
   At minimum: chaincase gasket; recommended: inspect primary chain & sprockets, check alignment, replace worn fasteners.

5. Is machining required?
   Dealers describe it as a direct replacement with no machining typically required (provided your model matches the KS 4-speed pre-2002 spec).