21/10/2011
The allure of endurance racing, particularly with diminutive motorcycles, is a curious one. It’s a test of machine and rider, a crucible where limitations are exposed and triumphs are forged in the fires of sleep deprivation and sheer grit. Having previously subjected ourselves to the trials of a Honda Grom and a Kymco K-Pipe in similar 24-hour challenges, one might think we’d have learned our lesson. Yet, the siren song of racing small-displacement bikes for an entire day proved too strong to resist, especially when a new contender emerged: the Benelli TnT135.
The Benelli TnT135: A Glimpse of Potential
Our initial encounter with the Benelli TnT135 was met with a surge of enthusiasm. Compared to its contemporaries like the Honda Grom, the TnT135 boasted a larger 135cc engine, a four-valve head, dual spark plugs, and a five-speed gearbox. These specifications, coupled with surprisingly attractive styling for its price point, immediately piqued our interest for another endurance race build. The prospect of pushing this affordable machine to its limits for 24 hours was an irresistible proposition.
The Build: More Than Just a Quick Fix
With the UMRA 24-Hour race circled on the calendar, we had a generous six months for preparation – a luxury compared to our usual last-minute scrambles. Benelli’s willingness to participate was a testament to either overconfidence or a genuine belief in their product. Our build philosophy, as always, was to see how a budget-friendly motorcycle could hold up under extreme duress. The TnT135’s foundation seemed solid: a capable 135cc engine with modern features like an oil cooler and fuel injection.
Engine Enhancements: Waking the Beast
The core of our build focused on extracting more performance from the TnT135. A key upgrade was the installation of a custom camshaft from Daniel Crower Racing. This bespoke component featured increased lift, longer duration, and more valve overlap, resulting in a claimed 2 hp gain and an 8 mph increase in top speed. While we couldn't independently dyno the bike, our estimates placed its power output in the 11-15 hp range. Complementing the camshaft were a K&N air filter and a Yoshimura RS-9T full exhaust system, allowing the engine to breathe more freely and sound considerably more aggressive. The final piece of the powertrain puzzle was a Power Commander module with revised EFI tuning and a quickshifter, aiming to optimise the air-fuel mixture and smooth out gear changes.
Modifying the handling proved to be a more intricate challenge. Fortunately, the TnT135 shared some component dimensions with the Honda Grom, allowing us to fit a K-Tech fully adjustable rear shock. The front forks, however, presented a significant hurdle. With diminutive internal cartridges, low-viscosity fork oil, and overly soft springs, the stock front end was prone to excessive pogoing. Our attempts to source stiffer springs or custom cartridges were hampered by lead times. As a last resort, we opted for a 20w fork oil, which offered a marginal improvement but didn't fully resolve the issue.
Ground Clearance: A Persistent Problem
A notable limitation of the stock TnT135 was its lack of ground clearance. The footpegs were positioned so low that they frequently scraped the tarmac, a fact evidenced by the chamfered edges on our bike. Even the sidestand mounting plate posed a clearance issue, requiring us to grind it down. While aftermarket rearsets are scarce for the TnT135, we explored options from China, though they offered minimal improvement. This lack of ground clearance became a constant consideration during spirited riding.
Gearing for Success: Optimising Acceleration
The widely spaced gear ratios, particularly between second and third gear, were a significant drawback for track use. This often left us either hitting the rev limiter in second or experiencing a substantial power drop in third. Superior Racing Sprockets came to our aid by custom-manufacturing an aluminium rear sprocket with two additional teeth. This modification not only reduced weight but also dramatically improved acceleration, making the TnT135 more competitive out of corners.
Race Day: The Test of Endurance
Our race team was a mix of seasoned veterans and enthusiastic newcomers. Despite the varying levels of experience, the shared goal was to push the Benelli TnT135 to its absolute limits while fostering camaraderie. The UMRA’s GP65 class, which we were placed in due to our 135cc engine, pitted us against a diverse array of machinery, including 65cc two-strokes and larger air-cooled four-strokes. We knew we were at a power disadvantage, but our strategy was to minimise pit stops and rely on consistency.
The Race Unfolds: Slow and Steady?
The Le Mans-style start saw us positioned mid-pack. It quickly became apparent that our TnT135, even with modifications, was outgunned in the straights by most of the field, including other minibikes. However, in the tighter sections of the track, our nimble Benelli excelled. The strategy of focusing on smooth inputs and hitting our lines paid dividends. Our two-hour fuel stints, fuelled by the TnT135’s 2-gallon tank, proved effective, allowing us to maintain a respectable pace. The only hiccup was the notoriously inaccurate fuel gauge, which made judging pit stops a challenge.
Triumphs and Tribulations
Against expectations, our consistent pace saw us holding third overall and first in class after our initial stints. This validated our “slow and steady” approach. However, as the 24 hours wore on, the superior outright speed of some competitors allowed them to build insurmountable leads. Despite our team’s best efforts, including a late-race stint from a rider who had missed most of the event, we ultimately finished sixth overall and fourth in class. The Benelli itself proved remarkably resilient, with only minor issues plaguing our run. A faulty Power Commander unit caused intermittent power loss, leading us to remove it and forgo the quickshifter. Later in the race, a blown fuse brought the bike to a complete halt, requiring assistance from fellow competitors – a true testament to the sportsmanship within the mini roadracing community.
One rider experienced significant discomfort due to the stock shift lever, resulting in a bloody toe by the race's end, a clear indication of the physical demands placed upon the rider and the machine. Post-race analysis revealed critically low oil levels, likely contributing to the shifting difficulties.
The Verdict: A Budget Champion?
The Benelli TnT135, despite its budget-oriented origins, proved to be a surprisingly capable machine. It endured a brutal 24-hour race with minimal mechanical failures, a testament to its robust construction. The areas for improvement are clear: addressing the limited ground clearance, refining the front suspension, and perhaps exploring more significant engine tuning options for future endeavours. The experience was not just about the race itself, but also about the camaraderie, the shared challenges, and the sheer fun of riding small bikes fast.
What We Learned:
- Performance: The TnT135, with basic modifications, offers a fun and engaging riding experience, though it lacks outright power compared to some rivals.
- Handling: While the chassis is competent, the suspension and ground clearance require significant attention for track use.
- Reliability: The bike demonstrated impressive resilience throughout the 24-hour ordeal, with most issues being minor or attributable to our modifications.
- Community: The spirit of sportsmanship within the mini roadracing paddock is exceptional, with competitors readily offering assistance.
Key Takeaways for Future Builds:
- Invest in adjustable suspension components.
- Address ground clearance with aftermarket rearsets or custom solutions.
- Thoroughly test fuel consumption to accurately plan pit stops.
- Ensure adequate oil levels and monitor for any signs of leakage.
Would we do it again? Absolutely. The Benelli TnT135 provided an unforgettable experience, highlighting the joy and accessibility of grassroots endurance racing. It’s a machine that punches above its weight, offering a platform for fun and learning for riders of all levels.
Frequently Asked Questions:
Q: Is the Benelli TnT135 suitable for daily commuting?
A: Yes, the TnT135 is a capable and economical option for daily commuting, offering a comfortable ride and good fuel efficiency.
Q: What are the main differences between the Benelli TnT135 and the Honda Grom?
A: The TnT135 generally features a larger engine (135cc vs 125cc), four valves, dual spark plugs, and a five-speed gearbox, offering a slight performance edge. Styling and ergonomics also differ.
Q: Are Benelli parts readily available?
A: Availability can vary by region, but Benelli offers online part diagrams and genuine spares to maintain and repair their vehicles. For specific performance upgrades, aftermarket support might be more limited compared to more popular models.
Q: How does the stock suspension perform?
A: The stock suspension is adequate for casual riding but is soft and lacks adjustability, proving a limitation during spirited or track riding, particularly concerning ground clearance.
Q: What are the benefits of using genuine Benelli spare parts?
A: Genuine Benelli parts are designed for optimal fit, durability, and safety, ensuring your motorcycle maintains its intended performance and reliability.
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