OK Guys, I’ll try and explain my thoughts on making this old lump go a bit better. I have no doubt I will once again be subject to scorn and derision, but WTF its all good clean fun.
Getting the boxer engine go better is about increased breathing. In other words bigger holes everywhere. The main problem is mixture. The engine in factory spec is set to run quite weak for emissions regulations. As soon as you do anything to help breathing, the mixture can go all to ffff pot. Some bikes (mine is one) come from the factory running borderline weak. For example, as soon as you stick a can on some of them, its running too weak in places and can actually run worse.
The cure is a chip which will enhance the mixture across a pre-set range, or a Techlusion box. The Techlusion allows you to fiddle with the mixture at low, mid and flat out throttle settings. This is my preferred option, cos its got more settings than you can shake a stick at, which suits me down to the ground. But it also means YOU have to fiddle with it yourself and it can be a bit of a faff on.
What Stef said about fitting a chip is dead right. Make sure the chip will compensate for a Y-piece, can etc.
GETTING THE GAS OUT: Easy, Y-piece and race can. Road cans don’t breath as much as race. But they do increase back pressure, which can help resolve mixture issues.
GETTING THE GAS IN: Also easy, K&N filter helps a little bit. Plus it has a 100k life so it is cost effective if you are keeping the bike a long time. RS inlet trunks. These are the plastic bits between the air box and the injector. The RS ones are a larger diameter and shorter. Once again lets more air in. You can buy these secondhand for less than £20 from breakers like
Motorworks (very helpful). Bigger inlet snorkel (the inlet thingy under the tank – to airbox) Expensive and you may only see an advantage very high up in the rev range.
Cams, the RS/S cams from the 1100 engine go straight in. Also helps to let more gas in but its hard to tell just what difference they have made. My feelings are, to gain full advantage of the cams, the compression ratio needs to be increased to that of the RS engine which is upping the ratio from 10.5 ish standard, to 11.5 RS. Which means skimming the heads. This is my next step, when I can be arsed. I just enjoy riding the bike too much to take it off the road for a week or so to do it.
All of these mods are pointing the engine away from torque and more towards horsepower. In theory this means loss of bottom end for an increase in top end. What has left me slightly baffled is, I have lost no bottom end after doing these mods. It still pulls like a train from 1500rpm. In fact its pulling in 6th better than ever. Where I think I have compensated for bottom end is by over-fuelling the engine in places with the Techlusion box. But I am still getting 50mpg…go figure. Mind you that drops off when I am on a mission to the low 40s.
The engine characteristic now is, pulls great and very easy up to 5000rpm then takes off like a scalded cat.
Now….., back to the Techlusion box. If I raise the compression ratio, I am almost certain that I will have to weaken the mixture in places. That’s why I went the Techlusion route, I can fiddle with it to suit the various mods on the bike.
Hope this helps…..lying down now
