1997 Honda CBR1100XX
Bronson the 1997 Blackbird was starting to give me the pip. Normally an ultra-smooth and quick ride, it was showing signs of hesitation at a steady throttle at more or less legal highway speeds. Fuel starvation? Hard to say. The weird thing was that if you threw the gearbox down a couple of cogs it would instantly pick up revs and accelerate away.
In any case, this first generation ’Bird – the only one to sport carburettors – was also notorious for having a mid-range flat spot that let down an otherwise slick performance. Blame the then-new noise regs, which encouraged makers to do things that they might’ve preferred not to.
So, in effect I had two problems to cope with: the hesitation, which was not standard, and the flat spot, which was. I hoped the first issue might be solved by carefully checking the fuel tap, lines, breathers and float bowls, removing any leaks, kinks or blockages. Oh, and check the coils, plugs and leads were all connected up properly.
An off-the-shelf solution for the separate flat-spot issue appeared when the bike was new, from US company Dynojet, in the form of a carb modification kit. Included with the instructions was a drill bit to bore out the breather holes on the carb slides, new longer springs with a different rate and adjustable main jet needles to replace the fixed original unit. It was also intended to offer enough flexibility to cover any minor mods, such as aftermarket mufflers.
This is all wonderful in theory, but first you have to get in to work on all this stuff. That takes an enormous amount of time, rather than skill. Bronson is typical of these sleek, fully enclosed performance bikes in that you pay for the looks when it comes to getting into the mechanicals. Fortunately, with 24,000km intervals between major services, that’s not something that has to be done too often.
Along the way, I found myself removing the seat, a couple of fairing infill panels, the airbox and dismounting the ignition coils. (I also removed the lower fairing, though that wasn’t required for this task.)
PLUGS? WHAT PLUGS?
Now here’s a tip, pretty much all that has to come off if you want to change the sparkplugs, which are still out of sight and buried deep in the bowels of the bike’s architecture. And then they’re only accessible with the help of the special, articulated plug spanner that comes in the stock toolkit! Guess what? I slotted in fresh plugs while I had the opportunity.
Along the way, I pulled out and dismantled the fuel tap. It and the carburettor float bowls turned out to be as clean as the proverbial whistle. Maybe that’s not so surprising given that, with about 57,000km on the clock, the bike shows every sign of having been in fairly regular use over its life and has been serviced along the way.
However, I did find some hoses were poorly installed last time it had been pulled apart, which may have been enough to set off that weird hesitation issue. Maybe I’ll never really know.
In the meantime, I’d ordered a new old stock Dynojet kit from the US. Installation was very straightforward. Again, just a slow and methodical process – something I can’t normally do without some sort of counselling, but muggins was having a good day.
The kit’s instructions were simple enough: drill out the breather hole in the slide, set the needle adjustment in the number three position, then change over that and the spring. Times four. Easy.
Reassembly was straightforward, despite the appalling number of fasteners that had collected in the nuts ’n’ bolts tray. Even better news: there were none left over when it had all been put back together! I hate finishing these jobs and finding there’s one mystery screw left over. The only thing that’s worse is realising you’re missing a spanner…
ON THE ROAD AGAIN
I’ve had cause to use Dynojet kits in the past and so was moderately confident the flat spot would be at least reduced. However, the mystery hesitation ailment was another matter. Yes, there were one of two things that might have been the cause, but nothing that stood up and waved a white flag. (Why more mechanics don’t have a drinking problem is a constant source of mystery.)
First task was to arrow on to the nearest freeway and run its length. The hesitation was gone and we once again had normal transmission. Lovely.
Get up it a little and the mid-range flat-spot was greatly reduced. It’s still not absolutely perfect and I suspect some quality time with a dyno and a good tuner would improve it further, but it’s now a hell of a lot better than it was and is more than acceptable.
All up the exercise cost a couple of hundred dollars and an afternoon, with a very happy result. Now, let’s get back to that sodding Sunbeam…
Blackbirds were built from 1996 (for the 1997 model year) through to 2007. There were three generations:
• 1997-1998: Carburettors, 22-litre fuel tank, 164hp claimed;
• 1999-2000: Fuel-injected, 24-litre fuel tank, two-deck tail-light, 164hp claimed;
• 2000-2007: Mixed analogue/digital dash, catalytic converter, 152hp claimed.
Several other running changes were made, for example a new front hub and discs between gen 1 and 2, plus alterations to the set-up of the linked brake system.
ONLINE OWNER GROUPS