TRIUMPH CRK CAFÉ RACER
John Nutting gets her running!
It’s always a pivotal moment in a rebuild when everything has been fitted to the bike and it’s almost ready to go.
Because the CRK 1200 Roadster I’d been building over the past year or so was non-standard, finding insurance proved to be more long-winded than you’d think. I was waiting for two companies to get back to me.
In the meantime I booked James at JB Motorcycles to carry out the MOT on the bike. The tank, mudguard and side-panels – beautifully painted in a shiny metallic red by Steve Coker – were fitted along with the seat.
For the tank badges I selected the same metallic items used on the latest Triumph Rocket 3 triples costing £30 a pop, but worth it for the authentic look. But I needed to position them correctly because I wasn’t confident enough to get them right visually. Gerry, who last year helped man-handle the four-cylinder lump in and out of the frame with his engine crane, is a sign-writer by trade and his trained eye was what it needed. Just as well: once the adhesive metallic lettering is pressed on, it stays on.
Methodically, Gerry did what he does best, and the CRK 1200 had an identity. The VIN plate had already been riveted to the sub-frame. So I made a few final checks. Fuel was reaching the carbs. The oil was topped up. There was a spark at the plugs. The trigger was correctly set. And the engine readily turned over at the press of the button. But it wouldn’t run, apart from a few pops and bangs from the exhaust pipes.
I was foxed. So I retraced my steps back to when I wired it up, something like six months earlier. Studying the wiring diagram for both the original Triumph
Trophy and the update digital C-box system I’d fitted, I was reminded that neither identified – to my understanding anyway – which way the two wires from the ignition box were connected to the coils. The ignition system is rather like those of many four-cylinder Japanese bikes, with the inner and outer pairs of spark plugs having a shared coil. The question is: which of the two wires from the ignition box goes where?
I suspected that I’d got them the wrong way round, so carefully removed the fuel tank, swapped the wires over and sure enough, even on the remaining fuel in the
carbs, the engine fired up. We were in business! Better still, it ran without any obvious problems.
By now the insurance people had replied. I’d sent pictures of the bike, told them what had been modified, suggested a value based on what I’d spent (more about that in the next part) and expected a huge premium. My usual lot (I won’t say who) after going upstairs to their specialists said they couldn’t provide cover, but Bikesure, bless ’em, came up with a premium of just £73 for a year, which was probably related more to my advanced years than any risk element!
Getting the MOT certificate was a formality, but reassuring nonetheless. It’s always good to get a second opinion and James, who had sold me the original donor machine for a grand, said he was impressed. “But it’s the wrong colour,” he added. “The DVLA thinks it’s blue and you’ve had it painted red. Better tell ’em.” The four-mile run to JB’S showed up a couple of other wrinkles that I’d have to sort out, though. The suspension was very stiff, hardly surprising because I had simply fitted a YSS rear shock supplied by Wemoto that was originally for the heavy Trophy tourer, and I’d not touched the front forks. Some wet roads showed that
CRK’S rear hugger was ineffective, letting spray get all inside the rear of the bike, so I replaced it with a used original plastic item sourced from Ivan at National Triumph. Also, I didn’t like the handlebar, which was too wide and low for my liking.
Adjusting the suspension could wait, but I couldn’t cope with the riding position. So I rummaged through a collection of handlebars stored in the roof of the garage and found a long-forgotten one that I’d intended for my old Norton 850 Commando. To my surprise the handlebar was swept back just as I like, and was an inch or so higher and two inches narrower, and even the switch consoles and bar-end mirrors fitted. But there was interference between the Domino twistgrip and the right-hand console, which a bit of fettling with files sorted out. Around the same time I tidied up the wiring by replacing some of the bulky 3.9mm Japanese bullets with smaller crimp connectors, and then wrapped the loom in textile adhesive tape.
Armed with an MOT and insurance I could now get the 1200 taxed for the road, and give it a shake-down run. I rode the five miles north to Ide Hill on the greensand escarpment and all seemed okay, except that it coughed a couple of times, missing a beat. But it carried on and I decided the following Sunday to ride the bike south the 25 miles to Heathfield, followed by Gerry on his Tiger 800. Despite the stiff suspension, the 1200 handled really well with neutral steering that felt also really secure. I was happy.
But at the top of Ashdown Forest the 1200 coughed again and after Buxted it stopped altogether. I figured it might be fuel, and after a minute or so the bike fired up again. But by the time we had reached the Shell garage opposite
Groombridge Motorcycles, it would only start and run for a few seconds and even then not respond to the twistgrip. I decided to cut my losses and call the RAC. Andy arrived after an hour or so, during which Gerry and I grabbed lunch at the Butcher’s Hook where other bike fans pitched in with their theories. Andy also thought it might be carb problems, but didn’t want to risk damaging the bike by pulling it apart. So a truck was ordered from Tunbridge Wells and we were back in less than hour.
Back at the garage I stripped the carbs and found nothing amiss, so re-assembled everything and fired it up. It was just the same though, stopping after a few seconds, but when I ran my fingers over the wiring adjacent to the ignition box after starting it once more the grey connection that earths the ignition came loose from the terminal block.
Was this the problem? I re-arranged the connections, and the bike started and ran reliably, but I couldn’t be sure if the carburetion was correct.
With a less restrictive air-cleaner and exhaust system, it’s normal to change the carburettor jets and needles to match the higher potential air flow rates. As mentioned in Part 7 of this series, CRK provides a kit which comes from Factory Pro in the US to change the idling jets, main jets and needles. While the original main jets are 127.5 for the outer cylinders and 130 for the inners, because these tend to run hotter, the Factory Pro kit provides 130/132.5 mains. To be honest, I couldn’t find much wrong with the response on the road, but then I wasn’t riding particularly quickly or accelerating hard. It felt okay.
In its instructions to find the best jetting, Factory Pro suggests carrying out on-road tests that involve hard acceleration in top gear, which to me means speeds of a ton or more. Without a track available that wasn’t an option.
I wanted more empirical measurements of the fuel metering, and luckily I have just the people on hand at HM Racing in Edenbridge, a 15-minute walk away.
HM Racing provides a range of services for racing teams, one of which is access to a Dynojet 250i rolling road dynamometer, which measures power and torque, which of course was of interest to me, but more importantly the mixture strength.
HM’S Tony Serafini, who is accustomed to checking fuel-injected racing bikes, strapped and set up the 1200 on the rig, using a feed from the left high-tension lead to tap the revs and fed an air sniffer pipe into the exhaust, after removing one of the mutes.
The first time you see a bike being revved hard on a rolling road it’s always alarming, more so when it’s your own machine. But Tony confidently checked that the transmission was okay before taking a couple of tentative runs through the gears.
Everything was in order, so he gave it a full-throttle blast up to 8000rpm. It felt flat at the top-end, with a peak power reading on the screen readout of barely 73bhp at the back wheel. Tony pointed to the line on the chart showing that the air-to-fuel ratio was very lean. From above 4000 it was 17 to 1, when for the best power it should be 14 to 1. “The main jets are too small,” said Tony. “And on these carbs, because the needles reach into the mains, that has an effect all through the range, not just at the top-end.” To confirm that the engine was running too lean, the choke was used to give some extra fuel and the peak power immediately jumped to 80bhp. Much more was possible, we reckoned.
Tony explained that the jet sizes are roughly the bore diameter in hundredths of a millimetre, meaning that a 100 jet is
1mm, so the jets fitted were 1.30mm and 1.325mm. To restore the correct fuel-air ratio from 17 to 14 to 1, my sums suggested an increase in jet’s bore area of 21% would be needed. With his seat-ofthe-pants experience, Tony reckoned an increase to 140 would do it. My 21% calculation came out at 142/144. I removed the carbs and returned them to HM. Jets were taken from their stock, and Tony quickly fitted them, and at the same time added a quarter turn out to the mixture screws to improve initial pick up.
After re-fitting the carbs and adjusting the throttle cable slack correctly, the 1200 immediately felt much more responsive off idle, so I took it for a run, taking in a bit of motorway, although I wasn’t really happy with the thought of the consequences if there was a problem. Gearing felt a little low, with 5000rpm showing at 70mph.
But it was fine, and I booked another session at HM. On the rolling road Tony immediately noticed the difference, and the first full-throttle run returned a peak of 97bhp. “That’s amazing,” he said. “Look at the fuel/air ratio. It’s about 14 to 1 all the way, with a bit of leaning right at the top. I don’t see better graphs with many fuel-injected bikes. You could fit slightly bigger jets to get that right at the top, but it might mess it up elsewhere. You’ll rarely be using 9000rpm anyway.”
I agreed. It looked spot on. But might more hard running help it reach the magic ton? After a couple more, it turns out that there was. The chart on the screen showed a peak of 100.34bhp at 8,100rpm, with peak torque of 73.3lb-ft at 6250rpm. “It’s probably never been run this hard for years,” said Tony. “It’s being cleaned out.” Now if it sounds like the peak torque is at relatively high revs, the graph also showed that it was flat right through the range, with no less than 66lb-ft between 2600rpm and 8000rpm. In other words, the throttle response would be strong all through the rev range, which is what I’d want for relaxed, but still fast riding.
For the original 1200 Trophy, Triumph claimed a maximum power of 108bhp at 9000rpm and peak torque of 76.7lb-ft at 5,000rpm at the crankshaft, which due to losses in the transmission of up to 15% can be diluted to 91bhp and 65.2lb-ft respectively at the rear wheel. So I reckon it had been improved.
HM Racing also provides suspension tuning services, which are handled by off-road ace Perry Leask. I asked him what he thought of the set up on the 1200. He pumped the suspension front and rear and his expression said it all. “It’s stiff,” he said, and after wielding his tape measure while we unloaded and loaded the rear end, added: “It’s sagging too much at the back. The rear-end should use about 15mm from full extension. You’ve got 35mm so add more preload.”
In effect the shock was operating at the stiffest rate of its travel, and the damping was also too hard, but with plenty of adjustment available, I could sort it out in due course. Next job was to get the fork legs serviced with adjusted preload, and Perry was just the person for the job. In less than an hour they were removed and dropped off at HM.
So next time, let’s find out what a retro CRK 1200 Roadster is like to ride when everything’s been sorted.