Honda GB350S (2025) – Technical Review

Rarely would a 20hp, air-cooled single be much of a highlight when it comes to new launches from a brand as big as Honda but the GB350S – hitting the European market at last after several years on sale in other regions – could prove a surprise hit as it cashes in on the rampant popularity of similar machines.

Affordable, simple bikes in the 300-400cc class have been flying out of showrooms over the last few years. In the UK market Triumph’s Speed 400 has a genuine chance of being the UK’s best-seller over 125cc in 2024, beating traditional market-leaders like the BMW R1300GS to top spot, and the market for such machines is continuing to grow even while overall motorcycle sales have contracted.

Pros & Cons

2025 Honda GB350S - Price

Honda has been showing a remarkable ability to undercut the competition with its new bikes over the last few years – with machines like the CB750 Hornet, Transalp and the new CB1000 Hornet all surprising with their combination of a low RRP and relatively high specification. The further down the market you more the more difficult it becomes to undercut rivals but Honda’s GB350S is doing its best to repeat the feat by coming in at under the £4k mark at £3949 when it reaches dealers in January 2025.

That puts it as close as makes no difference to its nearest rival, the £3899 Royal Enfield HNTR 350, and substantially undercuts the Enfield Meteor 350 or Classic 350 models. Given the sales success of those machines in recent years, Honda is well placed to cash in.

Three colour options are on the table, a pale ‘Puco Blue’, the pearlescent ‘Deep Mud Grey’ or a metallic black.

2025 Honda GB350S - Engine & Performance

If you want to rebel against the sheer weight of technology that packs most modern bikes then the GB350S might be just the machine you’re after: its spec sheet reads like something from an earlier century and shows that you don’t need all those gizmos to create an engine that’s fuel-efficient and eco-friendly. You just need to be prepared to take life at a more sedate pace.

With just a single cylinder, one overhead camshaft, two valves and a capacity of 348cc, the GB350S’s air-cooled motor even manages to look genuinely retro thanks to its near-vertical, finned cylinder. But it’s actually a new design, created specifically for this model.

It’s clear from the outset that performance wasn’t high on the priorities list, and Honda emphasises that the motor was designed with an eye towards low and mid-speed torque rather than outright power. A heavy flywheel helps, as does a coaxial secondary balancer that helps smooth out the delivery.

Clues to the modern origin of the motor can be found in the fuel injection system – mounted on an intake that’s again designed for low-end torque rather than power – and the use of low friction tech that includes a cylinder that’s offset 10mm to reduce side-thrust of the piston during the power stroke, plus an asymmetric conrod and a sealed crankcase with a bulkhead to separate the crankcase from the transmission. A reed valve in that bulkhead opens and closes as the piston moves and the pressure underneath it changes and an oil jet cools the piston and lubricates the big-end bearing. Oil is also used to strategically cool hotspots in the cylinder head, aiding the air-cooling and reducing temperature in that part of the head by 10%. Inside that head, the compression ratio is a mere 9.5:1.

While the peak power is only 20.8hp, it comes at a mere 5500rpm, and the max torque of 21.4lbft arrives at just 3000rpm. That’s in part because the engine eschews the idea of ‘oversquare’ bore and stroke dimensions – typical in most modern bikes, where the cylinder bore is greater than the piston stroke to encourage more revs and more power. Instead it’s a hugely under-square design with a 70mm bore and a 90.5mm stroke, putting the emphasis on getting as much torque as possible, at the expense of revs and power. Even the Royal Enfield HNTR 350, another bike with an under-square engine, doesn’t take the dimensions to that extreme, using a 75mm bore and 85.5mm stroke  to achieve a similar capacity to the Honda. The CB350RS’s peak power and torque figures are a whisker higher than the Royal Enfields but arrive substantially lower in the rev range thanks its more extreme under-square dimensions.

The retro cues don’t end with the air-cooled engine. It drives a gearbox with only five speeds, albeit through a modern-seeming assist/slipper clutch. Somewhat surprisingly, there’s even traction control as standard.

2025 Honda GB350S - Handling & Suspension (inc. Weight)

The steel cradle frame of the GB350S is just as retro as its engine, with a twin-shock rear end and right-way-up forks clad in old-school gaiters.

Honda claims that the chassis has just the right balance of rigidity and suppleness, and the geometry leans towards stability rather than rapid responses. A rake of 27 degrees is certainly towards the relaxed end of the spectrum, and the 1440mm wheelbase is substantially longer than either the Speed 400 or the HNTR 350, which both come in at around 1370mm or so.

Those forks are 41mm in diameter and offer 106mm of travel but no adjustability, while the twin shocks are nitrogen filled and give 120mm of wheel travel.

Brakes? Yes. There are some.

Oh, you want to hear more? They’re made up of a 310mm front disc with a two-piston caliper and a 240mm rear with a single-pot caliper. ABS is standard, as demanded by law, and the final all-important link between the rider and the tarmac is a set of Metzeler Tourance Next rubber, 100/90-R19 at the front, 150/70-R17 at the back.

Weight is 178kg including a full tank of fuel, just undercutting the 181kfg Royal Enfield HNTR 350 but squarely beaten by the 170kg wet weight of the Triumph Speed 400.  

2025 Honda GB350S - Comfort & Economy

A low 800mm seat height, wide, flat bars and a long, roomy seat combine with relatively low-mounted pegs for a riding position that promises to be spacious enough for most riders and shouldn’t cause any particular aches or pains. There’s nothing in the way of wind protection as standard but you can add a choice of screens – a low headlight cowl or a choice of two heights of standalone visors – to cut down on buffeting.

Economy is an absolute strong point of the low-revving engine, and under the WMTC measurement regime the GB350S achieves an impressive 94.1mpg. Combined with a 15-litre tank that’s a couple of litres larger than its main rivals can offer, that means you could manage as much as 373 miles from brimmed to dry.

2025 Honda GB350S - Equipment

As you might imagine, a retro-styled, low-cost single-cylinder bike like the GB350S isn’t packed with all the bells and whistles when it comes to the equipment list.

You do get the basics, though, including an LED headlight, a gear indicator set into the simple, analogue speedometer, plus a basic trip computer that gives fuel consumption readouts, estimated range to empty and an ‘ECO’ indicator to tell you if you’re sipping fuel as gently as you can.

There are a couple of more modern concessions including an emergency stop signal that flashes the hazard lights when you’re braking hard, and auto-cancelling indicators that turn off using a combination of front and rear wheel speed sensors to work out when you’ve completed a manoeuvre.

The options list lets you add to the kit, with a ‘Style Pack’ that includes a single seat cowl, the low headlight cowl, side tank pads, fog lights and different bar ends. Or there’s a ‘Travel Pack’ with the taller 355mm screen, 24 litres of saddlebag space, and hand guards.

Other options include the decadence of heated grips and a USB charger, and any of the components of the packs can also be optioned separately.

2025 Honda GB350S - Rivals

The GB350S’s main competition is likely to come from the cheaper end of the Royal Enfield lineup. The £3899 HNTR 350 is the closest model in price, spirit and style, but the similarly-powered Classic 350 (£4539) and Bullet 350 (£4709) must also be considered competition. The larger Scram 411, at £4849, could be another competitor, and the company’s new Guerrilla 450 at £5050 offers a lot more performance and tech in a similar section of the market. Triumph’s liquid-cooled Speed 400, like the Guerrilla, easily outguns the Honda in the performance stakes and much also be considered a key rival despite costing more than £1000 more.

Royal Enfield HNTR 350 | Price: £3899

Read more

Power/Torque

20.2bhp / 19.9lb-ft

Weight

181kg

Triumph Speed 400 | Price: £5195

Read more

Power/Torque

39.5bhp / 27.7lb-ft

Weight

170kg

Royal Enfield Guerrilla 450 | Price: £5050

Read more

Power/Torque

39.5bhp / 29.5lb-ft

Weight

184kg

2025 Honda GB350S - Verdict

By all accounts, the GB350S has all the right ingredients to be a killer recipe in the sales charts for Honda, and we’ll provide a full and detailed review once we’ve ridden the bike.

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2025 Honda GB350S - Technical Specification

What is MCIA Secured?

MCIA Secured gives bike buyers the chance to see just how much work a manufacturer has put into making their new investment as resistant to theft as possible.

As we all know, the more security you use, the less chance there is of your bike being stolen. In fact, based on research by Bennetts, using a disc lock makes your machine three times less likely to be stolen, while heavy duty kit can make it less likely to be stolen than a car. For reviews of the best security products, click here.

MCIA Secured gives motorcycles a rating out of five stars (three stars for bikes of 125cc or less), based on the following being fitted to a new bike as standard:

• A steering lock that meets the UNECE 62 standard

• An ignition immobiliser system

• A vehicle marking system

• An alarm system

• A vehicle tracking system with subscription

The higher the star rating, the better the security, so always ask your dealer what rating your bike has and compare it to other machines on your shortlist.