19/12/2002
Yamaha RD350 LC 4L0 Engine Rebuild - Episode 4: Stripping the Engine
Welcome back to Project Elsie, where we continue the exciting journey of restoring a classic 1980 Yamaha RD350 LC 4L0. In this instalment, we delve deeper into the heart of the beast as we complete the engine strip. Last time, we wrestled with the 'flywheel from hell', and now, with that vanquished, we turn our attention to the other side of the engine to assess the internal condition. The news is largely positive, revealing a powerplant that has clearly been well-maintained, despite its considerable mileage.
Beneath the Covers: A Glimpse Inside
Removing the engine side panel revealed a surprisingly pristine interior. While one stubborn bolt necessitated the use of mole grips, it eventually yielded. The clutch assembly appears almost new, and the gears are in pristine condition, showing little to no evidence of the 40,000-plus miles the bike has covered. This bodes well for the rebuild, suggesting that many of the original components will be reusable. The oil pump also seems to be in good order, with oil present in the exit pipes, indicating it was functional when the bike was last run. However, as a precautionary measure, especially given past experiences with autolube systems, the initial run-in after the rebuild will involve a 25:1 fuel-to-oil premix. This allows us to safely monitor the autolube pump's operation and bleed any air from the system without risking catastrophic engine damage.
The Scourge of Silicone and Stubborn Screws
A thorough inspection revealed the unwelcome presence of red silicone sealant in several areas, including the crankcase and water channels. While its ubiquitous nature is a testament to past repairs, its removal will be a time-consuming yet crucial step to ensure a clean and reliable reassembly. Fortunately, most of the other components, including the clutch and starter assembly, came apart with relative ease. The only minor hiccup was a small screw securing the input shaft bearing retainer behind the clutch, which refused to budge. However, as the crankcases can be split by removing just one of the two screws holding the retainer, this was a manageable inconvenience.
Yamaha's Ingenuity: Stamped Bolts and Clutch Secrets
Yamaha's attention to detail is evident in the stamping of numbers next to the bolts, indicating the correct removal and replacement order. This is a feature rarely seen on motorcycle engines and is a welcome aid during the reassembly process. A total of 16 nuts and bolts, in either 10mm or 12mm sizes, need to be removed before the crankcase halves can be separated. Upon closer inspection of the clutch, two surprising features emerged. Firstly, the metal plates are not perfectly round; each has a section removed from one side. Yamaha's design intention, it is believed, was to slightly unbalance the plates to counteract clutch noise through centrifugal force. While this innovative approach may not have been a resounding success, as it's not commonly found on other bikes, its correct reinstallation is vital. The cut-off sections must be spaced equally at 60-degree intervals between discs to maintain proper balance. On this particular RD350 LC, this spacing was incorrect and will be rectified during the rebuild.
A Crucial Component: The Belville Washer
A word of caution regarding the primary gear and pump drive pinion assembly on the end of the crankshaft. These are secured by a washer followed by a retaining nut. The washer in question is a Belville washer, a conical spring, and it is imperative to keep it safe and not substitute it with a standard washer. Its unique properties are essential for the correct functioning of this assembly.
Unforeseen Issues: Main Bearings and Gearbox Woes
With the engine fully disassembled, it was time to inspect the gearbox and main bearings. Unfortunately, not all the news was good. Two of the main bearings felt less than perfect. Given that the crankshaft will need to be disassembled anyway, replacing these bearings is the only sensible course of action. The gearbox itself has suffered significant damage, with 6th gear being particularly mangled. The extent of the damage suggests a catastrophic engine seizure at high speed. Both pinions will require replacement, adding to the list of parts that need to be sourced.
What's Next for Project Elsie?
With the engine parts list growing, further progress on the engine is on hold until the new components arrive. The next episode will shift focus to the brakes, a critical safety system that also requires attention. If the weather permits, the frame will be taken outside for degreasing, and any areas of rust will be addressed before a small amount of painting. Additionally, there is some electrical work to be done, including repairing a poorly executed fuse box modification. This project continues to be a challenging yet rewarding endeavour, bringing a classic Yamaha RD350 LC back to its former glory.
Frequently Asked Questions
- What episode number is the Yamaha RD350 LC 4L0 engine strip? This engine strip is detailed in Episode 4 of Project Elsie.
- What is the significance of the numbers stamped on the engine bolts? Yamaha stamped these numbers to indicate the correct order for bolt removal and reinstallation, aiding in the assembly process.
- What is a Belville washer? A Belville washer is a conical spring washer used to provide tension and absorb shock. It is crucial not to confuse it with a standard flat washer.
- What damage was found in the gearbox? The gearbox suffered significant damage, particularly to 6th gear, indicating a high-speed engine seizure. Both pinions will need replacement.
- What is the plan for the autolube system during the rebuild? The initial run-in will involve premixing fuel at a 25:1 ratio to safely monitor and bleed the autolube system.
Join us next time for more exciting developments on Project Elsie!
Article sponsored by Wemoto. Article provided by David Powell of Boston Bike Bits.
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