A guy at work who owns a 50cc Vivacity asked me about my spare Technigas Next exhaust last week and wanted to know if I still had it, as his standard exhaust was falling to bits. I told him I had and that he would need to jet his carb up at least one size to use it. I knew that his Vivacity had a 72 main jet as standard in it's Gurtner carb, so I wanted to aim for a 76 to 80 size main jet, but I didn't want to sacrifice a jet from my Polini jets kit. I needed a way to make a spare 72 size jet larger for him and my answer was this kit of pin drills that I bought over the weekend. http://www.maplin.co.uk/p/21-piece-miniature-drill-bit-set-with-pin-vice-a94qw These pin drills are ideal for re-sizing main jets on carbs. I matched one of the drills to an 80 size jet as closely as I could, and then carefully drilled a spare 72 main jet I had from an old carb, using the pin vice included with the kit. A dab of WD-40 and the drill went through nice and cleanly, leaving me with a jet sized around 78 to 80, just about right, as the drill that I used was very slightly smaller than an 80 size jet. Brass is self-lubricating when it comes to drilling, but a dab of paraffin or similar gives a much better finish to the drilled hole and makes the swarf stick to the drill bit, avoiding scratches to the bore of the hole. They are a bargain for a tenner and are worth keeping to hand, if you do a fair bit of carburettor or parts work needing small drill bits.
