Reviving Your RD350LC: The Crankshaft Rebuild

The Yamaha RD350LC, affectionately known as the 'Elsie', stands as an undisputed icon in the world of classic two-stroke motorcycles. Its exhilarating performance and distinctive sound have cemented its place in the hearts of enthusiasts across the UK and beyond. However, like any machine of its era, particularly a high-performance two-stroke, the longevity and reliability of its engine are paramount, with the crankshaft being the very heart of its operation. A well-maintained or expertly rebuilt crankshaft is crucial for keeping these legendary machines running as Yamaha intended, preserving their power and responsiveness for years to come.

While many two-stroke engines feature a pressed-together crankshaft assembly, the RD350LC presents a unique challenge that sets it apart. Understanding these intricacies is the first step towards a successful rebuild and ensuring your 'Elsie' continues to thrill on the open road.

The Unique Challenges of the RD350LC Crankshaft

Unlike many other two-stroke crankshafts where the crank pin is a separate, easily replaceable component, the 4L0 RD350LC crank features a design where the crank pin is integral to the inner flywheel web. This particular characteristic introduces a significant layer of complexity when it comes to assessing and quoting for a rebuild. If there is any wear to these crucial crank pins, it necessitates the purchase of a complete inner web replacement. Each inner web costs £37.50 + VAT, and with two of them required for a full replacement, this can quickly add to the overall cost of the rebuild.

The condition of your existing crankshaft webs is a critical factor in determining the scope and cost of the rebuild. It's simply impossible to tell what parts will truly need replacing without a thorough, professional inspection that involves stripping the crankshaft down. For instance, if a big end bearing has failed catastrophically, it's almost a certainty that a new inner web will be required due to the damage incurred. Conversely, if the crank has seen relatively low hours of use and has been well-maintained, there's a possibility that a standard rebuild, without the need for new webs, might suffice. This inherent uncertainty underscores why a 'quote' for an RD350LC crankshaft rebuild often begins with an assessment once the unit is disassembled.

Comprehensive Crankshaft Rebuild Service at PJ Motorcycle Engineers

Here at PJ Motorcycle Engineers, we possess the specialist knowledge and equipment required to carry out meticulous crankshaft rebuilds for the Yamaha RD350LC. Our process ensures that your engine's vital component is restored to optimal condition, meeting or exceeding original specifications for performance and durability.

The Standard Rebuild Process

Our standard crankshaft build involves a rigorous, multi-step process designed to address all critical wear points and ensure the highest quality outcome:

• Initial Stripping and Inspection: All components of the crankshaft assembly are carefully stripped down. Each part then undergoes a thorough cleaning process, followed by a detailed inspection for any signs of cracks, fatigue, or excessive wear that might compromise the integrity of the rebuilt unit.
• Component Replacement: We believe in replacing key wear items with only the best quality parts to guarantee longevity. In a standard rebuild, the following components are always replaced:
  • Con rods: Essential for transmitting power from the piston to the crankshaft.
  • Big end bearings: Crucial for the smooth rotation of the connecting rod on the crank pin.
  • Thrust washers: Control the lateral movement of the connecting rod.
  • Small end bearing: Supports the piston pin within the connecting rod.
  • All 4 main bearings: Support the crankshaft within the crankcases.
  • Centre labyrinth seal: Prevents oil and air leakage between crankcase halves.
• Quality Parts Assurance: We use only NEW, high-quality parts, predominantly sourced from Japan. This includes renowned brands such as Koyo and Hic Bearings, and Long Brand Con Rods, ensuring the rebuilt crankshaft meets the demanding standards required for a high-revving two-stroke engine.
• Precision Assembly and Truing: The reassembly of the crankshaft is a highly skilled operation. We build the crank on a specialised jig, which is absolutely critical for ensuring the crank is phased precisely at 180 degrees. This exact phasing is vital for the smooth and balanced operation of the parallel twin engine. Following assembly, the entire unit is meticulously trued by hand. This painstaking process corrects any minute imbalances or misalignments, resulting in a perfectly balanced and true crankshaft that is ready to be dropped directly into your crankcases, ensuring a seamless fit and optimal performance.

Pricing and Upgrade Options

The price for a standard crankshaft rebuild is £280.00 + VAT. For those seeking enhanced durability and performance, there is an option to upgrade the big end bearings to TZ style for an additional cost of £20.00 + VAT. This upgrade can provide an extra layer of robustness for enthusiasts pushing their RD350LCs to the limit or simply desiring the best possible components.

Logistics and Payment

We understand that getting your bike back on the road is a priority. Our typical turnaround time for a crankshaft rebuild is usually 10 days' workshop time, ensuring a swift yet thorough service. Payment for the service is not required until your crank is fully rebuilt, inspected, and ready to be sent back to you. We offer convenient payment options, including credit card, PayPal, or bank transfer.

If you require this specialised service for your Yamaha RD350LC crankshaft, or if you have any further questions, we encourage you to get in touch with PJ Motorcycle Engineers. Our team is ready to provide expert advice and assistance to ensure your 'Elsie' receives the attention it deserves.

Understanding the Heart of the Beast: The RD350LC Engine

The Yamaha RD350LC was a groundbreaking motorcycle, produced by Yamaha between 1980 and 1983. Although it immediately succeeded the larger RD400, the RD350LC was powered by a slightly smaller 347cc parallel twin two-stroke engine. Interestingly, this engine actually shared the same bore and stroke measurements (64 x 54mm) as the older RD350, demonstrating Yamaha's ability to extract impressive performance from a proven design.

What truly set the RD350LC apart was Yamaha's integration of liquid cooling, a significant advancement for two-stroke engines at the time. This innovation, coupled with other modifications in porting and exhaust design, was crucial for complying with the ever-tightening emissions regulations of the era. The RD350LC was primarily aimed at the European market, alongside its smaller sibling, the Yamaha RD250LC.

The 1980 to 1982 350cc models were famously codenamed 4L0 and quickly earned the affectionate moniker 'Elsie' among riders. While not officially sold in the United States, the model was readily available in neighbouring Canada, further solidifying its global appeal. The RD350LC's legacy continued with its replacement in 1983 by the RZ350 / RD350LC II / RD350 YPVS, a model that introduced Yamaha's revolutionary YPVS (Yamaha Power Valve System), which fundamentally changed the performance characteristics of two-stroke engines. However, the original LC (1) was also sold in that pivotal year alongside the newer YPVS model, highlighting its enduring popularity.

The Enduring Allure of RD350LC Restoration Projects

For many motorcycle enthusiasts, the Yamaha RD350LC isn't just a classic bike; it's a piece of history, a symbol of a bygone era of raw, exhilarating motorcycling. This deep connection often fuels ambitious restoration projects, transforming neglected machines back into their former glory. The journey of restoring an 'Elsie' can be a true labour of love, fraught with challenges but ultimately immensely rewarding.

Tales of acquiring an RD350LC, patiently waiting for its arrival in the early 80s, and then embarking on years of ownership filled with mechanical adventures are common. From holing a piston on a foreign tour to discovering long-forgotten manufacturer recalls, these bikes have certainly lived lives. One particular anecdote highlights the dedication required: an owner who, after a critical engine failure (an exhaust flange parting company with the barrel), left the half-stripped engine to 'fester' for over two decades before finally embarking on its much-needed restoration. Such stories underscore not only the mechanical intricacies of these bikes but also the profound personal connection owners develop with them, often leading to restorations undertaken as heartfelt tributes.

Undertaking an RD350LC restoration is not a trivial matter. It demands patience, meticulous attention to detail, and often a significant investment of time and resources. From stripping down a long-dormant engine to sourcing elusive parts, every step presents its own set of hurdles. However, the satisfaction of seeing a beloved 'Elsie' return to its original, or even better, condition, is an unparalleled reward. It's a testament to the enduring appeal of these machines that so many are still being brought back to life by dedicated enthusiasts.

The RD350LC's Legacy and Investment Value

When the RD350LC finally arrived in June 1980, after production delays that only amplified anticipation, it immediately lived up to its hype. Its impact was so profound that it was voted MCN Machine of the Year that very November. The following year, 'LC mania' swept across the biking scene, fuelled in part by the televised 'Pro-Am' race series, where the thrilling antics of riders like Mackenzie, Carter, and McElnea ignited a fervent passion for the 'Elsie'.

Decades later, the RD350LC remains a highly sought-after classic. Its original purchase price, around £1100 back in the 1980s, seems a modest sum compared to the value these bikes command today, particularly well-restored examples. For many, an RD350LC is not just a motorcycle; it's a cherished project, a link to their past, or an investment in a piece of motorcycling history. The enduring market for these bikes, combined with their relatively straightforward (though intricate) mechanical design, makes them a compelling choice for a restoration project. The availability of specialist services, such as crankshaft rebuilds, further supports the viability of these projects, ensuring that the legendary 'Elsie' can continue to be enjoyed by generations of riders.

Crankshaft Rebuild Options Comparison

Frequently Asked Questions (FAQs)

Q1: Why is the Yamaha RD350LC crankshaft rebuild considered complex?

The complexity of an RD350LC crankshaft rebuild stems primarily from the design of the 4L0 model. Unlike many other two-stroke cranks, the crank pin (the part the big end bearing runs on) is integral to the inner flywheel web. This means that if there is wear to the crank pins, you cannot simply replace the pin; you must purchase and replace the entire inner web, and there are two of these. This design makes it challenging to provide an accurate quote without first stripping the crankshaft down to assess the exact condition of these integral components, as their replacement significantly impacts the overall cost.

Q2: What parts are typically replaced during a standard RD350LC crankshaft rebuild?

During a standard RD350LC crankshaft rebuild at PJ Motorcycle Engineers, all components are stripped, cleaned, and thoroughly inspected for cracks. The following parts are then replaced with new, high-quality components, typically sourced from Japan (e.g., Koyo/Hic Bearings, Long Brand Con Rods): the con rods, big end bearings, thrust washers, small end bearing, all four main bearings, and the centre labyrinth seal. This comprehensive replacement ensures that all critical wear items are new, providing maximum reliability and performance.

Q3: How long does a professional RD350LC crankshaft rebuild usually take?

A professional RD350LC crankshaft rebuild typically has a turnaround time of around 10 days' workshop time. This duration allows for the meticulous stripping, cleaning, inspection, parts replacement, precision assembly on a jig (ensuring 180-degree phasing), and careful hand-truing of the entire assembly. This ensures that the rebuilt crankshaft meets the highest standards of quality and is ready to be directly installed into your engine crankcases upon return.

Q4: What type of engine powers the Yamaha RD350LC?

The Yamaha RD350LC is powered by a 347cc parallel twin, two-stroke engine. This engine shared the same bore and stroke (64 x 54mm) as the older RD350 but distinguished itself with the crucial addition of liquid cooling. Yamaha also incorporated other modifications to its porting and exhaust system to help the engine comply with the increasingly stringent emissions regulations of the early 1980s. This liquid-cooled, two-stroke twin was central to the RD350LC's reputation for thrilling performance.

Q5: Is the Yamaha RD350LC a good choice for a restoration project?

Absolutely, the Yamaha RD350LC is widely considered an excellent choice for a restoration project, albeit one that requires dedication. Its iconic status, engaging two-stroke performance, and strong enthusiast community make it a rewarding endeavour. While restoring an 'Elsie' can present challenges, such as sourcing specific parts or addressing age-related wear (like potential crankshaft issues), the satisfaction of bringing such a legendary machine back to life is immense. The bike's enduring value and the availability of specialist services for critical components like the crankshaft further enhance its appeal as a viable and worthwhile restoration candidate.

Conclusion

The Yamaha RD350LC remains a cherished classic, a testament to Yamaha's engineering prowess in the two-stroke era. To keep these iconic machines performing at their best, a properly functioning crankshaft is indispensable. While the unique design of the 4L0 model's integral crank pin presents specific challenges, expert services such as those offered by PJ Motorcycle Engineers provide a comprehensive solution. By entrusting your RD350LC crankshaft to specialists who understand its intricacies, replacing worn components with high-quality parts, and performing meticulous assembly and truing, you ensure your 'Elsie' continues to deliver the thrilling ride it's famous for. Investing in a professional rebuild is not just maintenance; it's a commitment to preserving the legacy and exhilarating spirit of this beloved two-stroke legend.

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