So I was down to Cambridge Motorcycles today and we ran the Kat up with the new engine. I can’t tell you how much I have been looking forward to this day. I was on tenterhooks as the new engine was an unknown quantity – being 27 years old, you can’t be sure of the history of an engine sold on as “stock” and who knows what horrors you may find when it’s finally run under load.

I can tell you that the Harris exhaust, chopped about as it is, is bloody loud. I wasn’t convinced as I’d been wearing ear defenders. After the dyno runs Spike fired it up. Think several angry rottweilers with attitude faced off over a bitch in heat! It sounds proper menacing! I don’t think it would make it through a trackday noise test. Something to worry about in the future, but for now, it’s just a means to an end. If we can make it work and get respectable noise limits out of it, I’ll keep it. If I can get enough money together for a Racefit Legend exhaust we’ll go for that during stage 3, when we big bore the engine.

As the stock motor stands, with 144 mains, pod filters, and the modded Harris exhaust we saw 119rwhp on the day. We have no torque numbers at the tacho pickup wasn’t working well enough to get power over revs, so the torque curve produced was meaningless.

So that’s a 33% gain in power over the air-cooled lump and with the significant weight saving I reckon that will feel quite a bit more spritely :o)

Spike at Cambridge Motorcycles will be re-running the bike during the week with slightly larger main jets as it’s running a tad lean at the moment. He’s also planning to play with the ignition curves using the Dyna2000 – so we may see a slightly higher number. What we get we get …. stage 3 will give us 150rwhp, so nothing to worry about anyway … Spring is upon us, and I want to ride the bike again, take some time to fettle the bike as it is, and take time out to save some more money for stage 3!

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Air-cooled vs Oil-cooled comparison attached

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Oh!, in other news the gearing might be a bit off. 11000rpm in top gives 180mph. Not so given we can’t really go smaller on the front – it’ll be 3 teeth added to the rear sprocket.

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