The Honda K4 didn’t make much of a splash when it made its debut over 30 years ago, but now the machine is a competitive force in the world of classic racing.
When you were at school you probably learnt that history was recordable and predictable. Christopher Columbus set off to discover America and the next thing there’s a Taco Bell in every shopping mall. The fact that Chrissy and his boys were looking for China and ended up in the Caribbean because their stolen maps weren’t big on detail is conveniently forgotten. Something definitely happened at somewhere clearly defined on a definite date: the end.
Motorcycling is the same. Take the Honda K4 for example. A dull, stone-axe reliable, commuter Twin which plods 59 zillion miles back and to work and carries rider, fishing rods and worms down to the river on a Sunday. Such a dull bike that it would not even be worthy of a footnote in the appendix of motorcycling history compared with the BSA group Triples, Honda 750 Four, Suzuki T20/X-6 and Desmo Ducatis of the time.
In fact, the K4 is so militantly innocuous that, except for the minuscule hole in the fabric of history, it would now be remembered by only the three founder members of the “Boring Japanese Bikes Register” based in Boise, Idaho. But the K4 did escape through that tiny tear and, at the other end, popped out as one of the great classic race bikes of all time.
Another short history lesson. For rather obscure but now very firmly established reasons, “classic” race bikes are deemed to be classic if they were in series production before 1973, in the case of four-strokes, and pre-1967 for two-strokes. These dates conveniently suit the current manufacturers of bikes based on the Manx Norton, Matchless G.50/AJS 7R and Aermacchi, and therefore the commercial pressure is to keep these arbitrary dates.
The final slice of history. By 1972, anyone with aspirations of winning anything in the 350 class was riding a two-stroke. Whether a standard Yamaha or specials like Seeley-framed Yamsels, only those who lacked the necessary finance were still using four-strokes.
What makes a bike a classic? Well, the arbitrary guidelines enforced by classic racing (at least in the British Isles, where Frank is from) are pre-1973 for four-strokes and pre-1967 for two-strokes, meaning the Baker-framed K4 just makes the cut.
One of these low budget racers was Terry Baker, who was working for RB Racing in London. Terry was given the then newly launched K4 road bike to race by his employers but soon found the standard frame lacking – almost to the point of being dangerous. Taking inspiration from the TZ Yamaha, Terry produced his own frame – and sold nine of them before the critical 1973 cut-off date.
Fast-forward 30 years and Terry has relocated to very edge of west Wales where the air is clean and workshop space is cheap. Now, we find Terry making alloy tanks for race bikes but still with the drawings for his original K4 to hand – and the receipts to show that the chassis was in production in 1973.
By 2006, classic racing has become a serious and expensive exercise. A typical price for a race-winning replica AJS 7R nudges $45,000 – and maintenance cost is at MotoGP levels. The idea of the ordinary working guy loading up his home-built trailer and having a bit of fun on the cheap is long since gone.
The salvation for classic racing lay in the K4 and, despite what the glitterati who inhabit the exotic end of the racing spectrum might say, competitive racing in Britain, and world-wide, would be much weaker without the cheap, reliable and fast K4.
If you have a K4 handy, a $2500 investment in Terry Baker’s race kit will upgrade your machine with an alloy tank and lightweight frame.
Enter, then, Terry Baker. Even with inflation, Terry can supply a complete K4 race kit, including alloy tank and one of his lightweight frames fabricated from annealed 4130 chrome-moly tubing, for a base price of $2,500. The result can be a proper, serious racing motorcycle at prices which the (committed) working-class hero can afford.
One of the greatest fans of the Baker-framed K4 is Rob Monroe. A talented motocross rider and engineer, Rob drifted into the classic road world, found he was rather good at both riding and tuning, and so set up a K4 tuning business. Now that’s easy to say but most of us would not go quite as far as building a very large shed in the back garden and installing $40,000 worth of rolling road in it. Rob is serious about racing!
The dyno is a hard-hearted instrument. You run the bike and it tells the truth. Not how well the rider thinks the bike is performing but the brutal figures. The dyno says Rob’s K4 engine produces over 50 bhp – and that’s an awful lot of power from a commuter Twin.
Rob undertakes a vast amount of engine work on the K4, ranging from that which might be expected, such as gas flowing the cylinder head and the addition of a hot race cam, to some really detailed engineering, even down to using titanium-nitrided wrist pins. A tweaked up commuter engine this is most definitely not! The final result is a powerful but very rideable motor with impeccable reliability even when ridden very hard.
The venue for this test was the Auto 66 Club’s hillclimb at Elvington. This event is held on the old nuclear bomber base near York and, not unsurprisingly, the runway and perimeter roads are flat and the expanses are huge which the big, old jet bombers demanded when they were trundling up and down ready for the start of World War III. Despite being flat, Elvington is one of the best hillclimbs in Britain, being a mile in length with a range of corners from a tight hairpin to a flat-in-third, left-right which really tests the handling of the bike – and the nerve of the rider.
Classic racing has become a serious business, with bike and upkeep costs reaching dizzying heights. The beauty of the K4 is the accessibility in price allows a great deal more enthusiasts to participate in the sport.
I also like the surface at Elvington. I am not one of the world’s great racers but I’m not too bad on tarmac tracks which have ruts, potholes and jumps in them. When I began racing, there were plenty of airfield courses, so I have never lost the knack of being able to ride these rough, homemade tracks. Elvington is as rough as they come and also has a surface whose adhesion might generously be described as qualitatively some distance from that gracing a modern race track. In short, Elvington is a wonderful place to test a classic road race machine.
The first thing which impresses about the bike is its size. Although having a short, 52-inch wheelbase, there is ample room on a Baker-framed K4 even for a big lump like me. It’s not like the huge expanses of a Manx Norton or G.50, but compared with my ultra-compact Seeley it’s quite palatial.
Starting the K4 is simple. Choke on, a bit of assistance from Rob, and the Honda motor bursts into life immediately. The engine is simple to catch on throttle once it has fired and the noise is truly delightful. Many race bikes which begin life as road-going motorcycles still hang on to their more mundane origins and sound like Proddie racers with the silencers removed. By contrast, the K4 produces a strong, tenor war cry which is worth coming to Elvington just to hear. In every way, this could be an exotic Italian Twin from the 1960s.
The Elvington circuit used to play host to Britain’s fleet of nuclear bombers but nowadays it’s classic motorcycles which rip about on the tarmac. Frank fires up the Baker K4 and gets ready to show Elvington what’s what.
The good news gets even better. Unlike its thoroughbred contemporaries, the K4 is simplicity itself to ride. Getting to the start is no more complicated than feeding in the clutch and burbling down to the timing lights just as if it were in its original commuter trim. The bike will pull well from 1300 rpm and simply gets faster the more one opens the throttle.
The first practice run was even more of a culture shock. Once on the track, the electric-smooth engine really comes into its own. The fat part of the powerband is from around 6,000-11,000 – a truly hugely forgiving spread for a race bike – and kept there the K4 flies. Elvington is a strange place to ride, to some degree, because the initial straight is vast both in terms of width and length. With no other bike in sight it is easy to lose sight of just how fast the K4 is gobbling the distance, but the speed at which the corner marker boards arrive shows that it truly is getting on with the job.
During the lunch-time high cholesterol break (classic racers need a daily intake of saturated fat to keep their Super Size figures suitably rounded), Rob stresses to me that his K4 is not tuned within the last inch of its life. On the contrary, subject to extremely regular changes of its fully synthetic lubricant, he expects one of his 50-bhp engines to go a whole season without a strip down. This is in stark contrast to the replica AJS and Manx Norton engines which need a fortune, in both time and money, pouring into them if they are to stay competitive and reliable.
Synthetic lubricant was one thing the orginal K4 didn’t have at its disposal, but K4 engine tuner Rob Monroe plans on utilizing the new stuff in hopes of making it through an entire racing season without having to strip down the engine. A feat which the K4’s classic racing competition would have a difficult time matching.
There is always a danger of trying too hard when racing a borrowed bike. No one rushes over to congratulate the journalist who has just stuffed a race bike into the tire wall and wrecked it. Even so, as the afternoon progressed I got ever more enthusiastic. The great joy of the Baker-framed bike is that it flatters a very ordinary rider like me. There are many quick bikes about in classic racing, but if they require skill or courage to ride, then their charms pass me by. The K4 simply solves all the problems for the pilot.
At Elvington, there is one particularly nasty rut-cum-pothole which would unsettle any race machine. The K4 got marginally airborne over it, landed, wiggled its head and then instantly settled down without the slightest input from me. Even more impressively, no steering damper is fitted. Rob sings the bike’s praises in the Isle of Man and I can understand why.
The motor is sweet, willing and easy to ride with a light, positive gearchange. The lightweight Honda 750 front brake, gripped by an AP caliper, is powerful with lots of feel, and the Maxton front and rear suspension impeccably calm. In short, it is a nice racing motorcycle.
My times fell steadily throughout the day and, on the last run, I had so much confidence in the bike that I decided to have a serious go. Before the final straight, there is left-straight-right complex which, if done correctly, can really reduce times. On my Seeley Suzuki, it’s a real struggle for a rider of my ability.
After some time in the saddle to get comfortable, Frank was tossing the K4 with a little bit of swagger as he carved up the bumpy, pothole-strewn Elvington track.
I pitched the K4 wide into the first left-hander, using the gravel-strewn edge of the tarmac, then simply nailed it hard in third all the way round. Rob’s Honda skated and slid on the bumps but was so stable that I was able to keep it hard on the throttle just knicking into fourth on the exit. This gave me an average speed of almost 60 mph from a standing start, fast enough to win the 350 class but also sufficiently quick to be the fastest classic. Not bad for a dull commuter bike ridden by a very ordinary pilot.
Rob will build a brand-new Baker-framed K4 for you, or tune a K4 race or road bike to whatever standard you wish. But the best fun of all would be to take a standard K4 road bike and let Rob tweak it into a 120-mph Bonneville/Commando/Ducati-destroying stealth bike. If I win the lottery…
For more information contact Rob Munro on International + 44 1524 846 190 or Terry Baker International + 44 1974 821 469
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