PROJECT STREET SLEEPER: PART 8
The heart of any twostroke motor is its exhaust, specifically the expansion chamber. For me, box-pipes were hideous things, but over time my perspective on this has changed considerably.
Power hungry yoof
I always used to be the guy chasing more bhp, it was my quest… I loved the challenge. Within tuning, the expansion chamber is king. It can tame a motor with peaky port timings and deliver a tonne of low-down torque, or it can allow the engine to sing-on at high revs, and reach its full potential. Box-pipes, however, are functional items, built to be robust, compact and effective… as emission and sound silencers. But over the years, as we look back at the classic lines of the Lambretta scooter, we have to acknowledge that the clubman-style exhaust is part of the iconic styling silhouette that we lust after. I recall when the new Lambretta V-Special was released and they had neglected to fit the link-style forks we all recognise in favour of straight tubed items. An outsider would take the financial economic gains in that decision, whereas an enthusiast would take the style option. So, when it came to styling my street-sleeper scooter, the original silhouette is what I desired… as best as is possible when creating something of this nature. And when I was told a prototype clubman-style pipe was on its way to me, I was delighted!
All in… or all out?
When it comes to exhausts, I have to be either all in or all out. By that I mean it either has to be all about the performance or all about the styling… no compromise will do. This was a bit of a problem when the first pipe arrived, the one which came with the engine, because it was a 2-into-1 expansion chamber. That compromise essentially reduced the spine-tingling sound of the beautiful purring twin, and also reduced the power output when compared to a full set of independent twin pipes, which would have both sounded better and given more power! Nobody ever saw HRC fitting 4-into-1 pipes on to Mick Doohan’s 500cc V4 GP bike. So, if you want power from a twin-cylinder, twostroke engine… then fit twin pipes! They look shit hot, sound awesome, and perform to the best of the engine’s ability. Thankfully, this problem was solved when both of the other more definitive options came to market. The 2-into-1 system was a compromise, whereas twin-pipes, or a box-pipe, were not. One was all about the power, the other about traditional/classic styling. Given this is a street-sleeper, and a rusteration project, for me it had to be the box-pipe. No doubt.
The goods
When the pipe arrived I got straight on with fitting. You know the job in hand; you think about it over a brew in the kitchen before you march out to the garage clutching the new component. But it’s always the same, isn’t it? In your mind it was a bracket, a few springs, and a couple of nuts in order to get the pipe fitted. Probably a half-hour job, and then I’ll be back inside for Homes Under the Hammer. But that’s never the way. Straight off the bat, I couldn’t get the bloody double manifold to slot on to the stubs. Various lubes were tried... loosening of this, tightening of that, and then it became apparent there was a problem (isn’t there always?). The weld inside the manifold hadn’t been filed down sufficiently, and was gouging a wedge against the stub. It would never go on. So, it was out with the Dremel. Problem solved! Well, almost. That modification did allow me to get the
manifold fitted. However, I then spotted that the main body of the pipe was now fouling against an engine case stud. So, off again with the pipe, and a modification to the length of the stud. Right, sorted! Well, almost. Now the main bracket on the body of the pipe, which fits to the engine casing, isn’t quite lining up. Damn, more modifications! The same again as I started to tighten up the rear silencer; everything seems a bit too much under tension for my liking. So, I slackened everything off, made a few more adjustments, and nipped everything in place. By now I’d been on with this for three hours, and even missed Dickinson’s Real Deal… outrageous. I reflected on that time spent, and it reminded me of those shitty situations when I ran Scooterotica Dyno centre, and a customer wanted a pipe fitting, and then a dyno. In his mind I should have fitted the pipe for free, as it’s ‘only a five-minute job’! But certainly from my perspective, even on jobs like that one, I never charged anyone for the full hours of fitting a ‘problem component’, despite it being my lost earnings. You just sucked up those losses and hoped to claw it back somehow. But the time spent on this pipe wasn’t a commercial situation for me, thank god, it was a labour of love, and damn it was worth it. The pipe looks absolutely stunning (in my humble opinion). It couldn’t look more at home on this machine; it fits into what I am trying to achieve just perfectly. I know it won’t sound as good as twin-pipes, or have the same power (not by a long chalk), but it does look good, so I’m happy. That’s all for this month. Stay tuned.