The lad who owns this DRZ450SM had been riding it on a restricted licence at 33bhp. He’d got through that period and wanted to liven his bike up a bit, so put on a full Scorpion exhaust system. Unfortunately he’d also read – and believed – t’internet and had cut a whopping great hole in his airbox…

Now that sets alarm bells off around here for various reasons. We could get enough fuel through it for the main jet but not enough on the needle in the upper mid-range. So we had to close his airbox down to a size where it wasn’t as restrictive as the original but flowed correctly for us to fuel it right.

In the end it made a sweet 38bhp. And ‘experts’ on the internet are not always to be believed…

Uncorked with a re-constituted airbox...

Uncorked with a re-constituted airbox…