Can Chops by Mad_Ax This subject comes up quite a lot, so when I was chopping my new G-Force can on Sunday afternoon, I decided to take some photos and put together an illustrated "how to chop your can" document, for the benefit of anyone else wanting to do this job but unsure how to proceed. I hope that if this is of use, the mods can put it into an FAQ or technical articles section when the site is re-vamped. Tools you'll need: - CD-R marker pen, or similar that will mark the surface of your can - Set square and/or ruler - Sharp hacksaw - Power drill and sharp bit to remove rivets - Draw file Safety advice: Fibreglass wadding (using as sound deadening in the can) is horrible stuff. I advise wearing gloves when handling this stuff, as it irritates the skin. If you intend to cut with a power saw rather than a hacksaw, then I also advise using a dust mask, as fibreglass dust is very abrasive and can cause problems in soft moist places like mouth, nose and lungs. As always, you should follow standard workshop practices when working with power tools - if you don't know what they are, put the power tools down and go play with your crayons. First off, here is my shiny can, built by G-Force. I'll start by singing the praises of this can and the company that supplied it - Mike at G-Force was really helpful, and spent a lot of time listening to me when I described to him what it was I wanted, and when it arrived, it was spot-on. Basically, it's a custom version of their new "Big One" - a big-bore tailpipe, instead of a little cocked spout. I explained to Mike that I'd be fitting it directly into the aftermarket Bandit 1200 collector box on my 1127, hence the can would be mounted underneath the bike, on its side, and pointing very slightly to the right with the angle of the collector. There would be no intermediate pipes - the can was to fit straight into the collector box. Mike had a set of b12 headers in the workshop, so he was able to ensure that the inlet pipe would be of the right diameter. As you can see from the picture in the post above, Mike even went to the effort of mounting the G-Force plaque on the side of the can, so that it's visible from its mounted position on the bike. At last - a man that actually LISTENS to what I'm saying, instead of nodding and saying "uh-huh, yeah" and then just doing whatever the hell he feels like... There was one problem, and that was my fault. When I calculated the length of the can, I measured the position of my Bandit 600 headers relative to the frame, because the new 1200 headers had not arrived at that time. When I came to fit up the pipe, I realised that the b12 collector box sits several inches further back in the frame, meaning that my shiny new can was too long. It actually fitted OK, because the angle of the collector box kept it from hitting the rear wheel, but ground clearance was severely reduced. The picture below shows what happened when I tried to take a nearby roundabout... That's one way to remove a "not for road use" marking So I needed to remove around 2 inches from the can. The first thing to do is to remove rivets (and outer strap, if fitted) from the end cap (I removed the cap at the inlet end, as this is the least visible part when fitted, so it doesn't matter so much if it's not 100% tidy). I did this by drilling the rivets out with a crown-tipped drill bit, however you could use a dremel grinding disc. There are 5 rivets on my can. Once the rivets are drilled out, the outer strap can be removed. Many cans don't have these, and I didn't intend to refit the outer strap on mine.* With the strap and rivets removed, you can measure the desired length from the end of the metal sleeve, and make lots of little marks around the can. If you can, use a set-square to ensure your marks are all at the same length. When done, join up the marks to make a straight line around the can. I used my outer strap as a bendy ruler to help joining up the lines. Advice: CD-R marker pens are perfect for this job, as they're permanent and don't smear. I always keep one in my workshop as it's dead handy for marking things onto metal or plastic components. *This is in fact a lie. I was going to refit it, but it got caught in the drill as I was cutting the last rivet, and it span around, cut my arm, and got all kinked in the process. Whoever said this was going to be easy..? Now, carefully cut around the can. It's best to do this by cutting an inch or so down then rotating the can, so that you don't cut through the perforated tube in the middle - you'll need that for later! The vice in the picture is very special to me. I only bought it so that I had an excuse to ask out the girl on the checkout in the DIY store. If you're going to use a vice, make sure you don't tighten it too much on the inlet tube, otherwise you might warp it. If you're going to ask out DIY store girls, make sure you wear body armour because they're all nuts. Note also that the sheet metal used to make the sleeve on an oval can has a tendency to want to return to its natural shape, i.e. flat. It can't do this, because it's seam-welded, but it will tend to warp and flex as you cut, which can seize the hacksaw blade. Much patience is required. This also causes additional problems, which we'll get to later. In the picture you can see that the larger section has warped into a different shape without the support of the end cap (see the difference in height on either side of the cut). Once the chop is complete, the end cap should (in theory) pull out. My G-Force can was very easy to seperate, although the Yoshi that I chopped last year was a ferkin' nightmare, because the end of the perforated tube was a very tight fit into the opposite end cap. If your can won't separate easily, check the perforated tube isn't welded or riveted to the end caps at both ends. It may also be necessary on a very tight-fitting can to make a longitudinal slice in the discarded section of the sleeve so that it will come free from the end cap. This was necessary on my Yoshi, and also on the crash-damaged titanium Ixil that I repaired earlier this year. In the photo you can see the fibreglass wadding escaping from the opened can. Be advised that this stuff is bloody horrible and gets everywhere, and makes your skin itch to buggery. Some stuff is thicker/heavier than others; the lighter the pile, the more it irritates. If in doubt, wear long sleeves and consider wearing a dust-mask if you're cutting with power tools, as it makes a nasty mess of soft moist lungs... Here you can also see that this particular can has a widened performated tube at the end. This is annoying, since we'll need to chop this off to get the can back together. Next task is to measure how much of the perforated tube you need to remove, and chop it off. If your can has a widened end piece, you could cut this off seperately and weld it back on in the right position. The widened piece on the G-Force slips over the tailpipe, to hold the perforated tube still and seal in the fibreglass wadding. I didn't bother with mine, as the tube is actually a snug fit inside the tailpipe outlet. When the perforated tube is cut, test-fit the whole assembly, and make any necessary corrections or adjustments. Note that re-fitting the end cap can take some whacking, so don't worry about getting a tight fit at this stage. When you're happy with the fit, disassemble the can and tidy up your cuts with a draw file. Once this is done, you need to put the whole thing back together. My can was very light on the fibreglass stuffing, but I kept a tin full of wadding from previous can chops, so I gave the G-Force a bit more stuffing. This helps to deaden the sound (shortened cans are obviously louder than long ones) and will also absorb any rattles that the perforated tube makes. With the can re-stuffed, slide the tube and the end cap into the sleeve, taking care not to force the stuffing out of the outlet. If you have an oval can, you'll probably now discover that the outer sleeve has warped to form a more circular shape. Trying to squeeze it by hand is probably pointless - now's the time to hop to the DIY store and purchase a big fat vice from a little slim girl, if you don't already have one. You can use this to press the sleeve back into shape while you push the end cap in. Make sure you use some thick rags or slivers of wood in the vice jaws to prevent scratches on your lovely can. Once the end cap is pushed in by a millimetre or so, you can release the can from the vice and bang the end on a wooden block placed the workbench to force the cap in quickly. Take care if your can has a pressed steel end cap, as it might bend (my Yoshi bent by a few degrees, but no harm was done as by pure chance it actually made the can sit flush with the frame) If you have a cast end-cap (such as on a bolt-on can) you can bang away as hard as you like. Once the end cap is in place, check it all over for alignment and make sure that the stuffing isn't escaping from the other end. When you're happy, drill yourself some more holes and rivet the end cap on with good quality rivets. Here you can see my finished product, good as new, completed in less than an hour Note that you can also use this method to repair a crash-damaged can. This is an Ixil titanium bolt-on can that I repaired by separating the end caps, removing the damaged section, and replacing the end caps again. This is the fixed can: And THIS, believe it or not, is the damaged section that I cut out of the can. Note: In a fight between a modified zx6r and a milkfloat, the milkfloat will win.