The recent Yokohama Hot Rod Custom Show proved once again that there is absolutely no let up in the land of the rising sun, as the country’s custom builders continue to turn out one masterpiece after another. From full-blown show bikes to those thrashed for thrills on the race track, the attention to detail is simply incredible. Of course, Kengo Kimura of Hiroshima’s Heiwa Motorcycles was in attendance with another one-off custom creation for the ages, but now he’s starting 2023 with a bike you could use for your daily commute and sports a feature that is new to the work of the master builder. Enter the Heiwa Triumph Bonneville T100 No. 4, which unlike the other bikes in the series or anything he’s built before, sees Kimura-san jump into the world of water cooling.

That’s right, for all the hundreds of custom motorcycles that Kengo Kimura has built over the years, this is the first that I’m aware of that features a water-cooled engine. Obviously, I’m sure he’s spun the spanners on such a machine, but going through his incredible portfolio, this was the first liquid-cooled motorcycle I could find among them. This is not unusual for many custom builders, especially those who focus on American v-twins, classic British bikes and the clean lines of the many retro-inspired motorcycles that come from Japanese manufacturers.

Water cooling by its very nature adds more components to deal with, but importantly, keeping the lines clean while working with an unfaired bike hosting a radiator, pipes and pump, offers a serious challenge. And it’s one that Kimura-san has met with all his might and proves that the master can transfer his style onto just about any machine you care to name. The 2019 model machine was rolled into his port side workshop and was stripped down so he could cast his eye over the redesigned Bonnie.

The first step to turning the remade retro into a Heiwa ride was to get the stance right and that begins with a change to the wheels. The rear end cops the biggest change with a drop down in size to a 16in wheel in black that has been relaced to the stock hub. The front end stays at the stock dimension, but a new rim and spokes get the look just right. Sticking with the best of British, both ends are wrapped up with vintage Avon rubber, in the form of SM MKII’s, which begin the process of transforming the bike into an even more classic look.

With this done, the bike was of course sitting at an odd angle and a suspension change was in order. The front end has the forks rebuilt and dropped through the triple trees, while at the rear, the ride is drastically improved with a set of custom length Kayaba shocks.

The top tree was then cleaned up and prepared for the new controls, another area where Kimura-san excels with his signature style. The risers and bars are each one piece, brilliantly bent to form the low bob look, with a single piece slotted between the two to form a brace. The picture-perfect welds are then smoothed out before the whole thing is powder-coated black.

More fabrication follows and the bodywork is all made by hand, using the same tools that master craftsmen have relied upon for generations. The fuel tank posed another new challenge for Kimura-san, having to ensure enough room was allowed for the internal fuel pump to operate properly on this EFI ride.

But as always the lines that have been hammered and rolled from raw aluminium sheets are flawless, with smooth flowing curves and nice knees dents to allow the rider to really tuck in. A custom set of mounts position it over the backbone and ensure the bottom runs perfectly parallel to the ground.

The rest of the metal work is just as good, with the side covers designed to slot into the triangle cutouts in the frame and hide a host of the electrical work that sits behind them. The front and rear fenders were both made for the job and the smooth lines of a hand-rolled item always looks brilliant.

But the rear end did require some modification to the frame rails, enter the angle grinder, so that everything sat level. The paint job was handled by ACN, with Kimura-san picking a subtle bone white colour which is offset with simple black graphics.

This work perfectly with the signature Heiwa seat in black leather, and the look is completed with the company’s own full lighting package, with the rear fender mounts finished to match the housing of the brake light. Now a little extra power could be extracted from the water-cooled twin, and helping it to breathe more air is a high flow filter.

The exhaust is a custom job, with the headers converging on the right side of the bike, before ending at the back tyre with a pair of slightly offset megaphone mufflers, a tip of the cap to ’60s British bikes.

The end result proves irrefutably that a style honed over decades can work wonders on a modern machine, so who knows what’s to come from Heiwa.

[ Heiwa Motorcycles ]