Big Bore Pistons & Cylinders
I've had several emails pop up on the specifics of doing the 2mm overbore. There are 2 ways to do this overbore. One is to use the stock ZG1000 bottom end, stock rods, ZX11 (c or d) pistons, and have the cylinder deck shaved .040". this will make the compression appx 11:1 . The cams will be retarded by the decking, and since you're hotrodding the cams should be re - dialed in. I've found 103 / 103 a nice compromise.
The other combo is more involved, and more geared toward someone fixing a previously hydro'ed engine w/ a bent rod. This combo uses ZX10B connecting rods (88-90) and ZRX11 pistons (any year). This combo will give you longer / stronger rods, 11:1 compression, and not effect the cam timing.
Both setups need to have the head gasket bores relieved 2mm, which can be done with a die grinder and about 4 hours of patient work. There are enough landmarks on the gasket to keep your metal removal limited to a more or less round bore when you're finished. You could also have Cometic gasket custom make a gasket - that's the direction I went with the 1109, as 4 MM is to much to remove from the stock zg1000 head gasket.
Using used pistons / rings is completely acceptable IMO, as long as they're not exhibiting prohibitive wear. Of course you need to know what you're looking for, but these parts aren't like chevy 350's, Kawasaki's stock parts are almost bulletproof, and re-using low mileage parts is the only cost - effective way to go.
Have the block bored w/ .0025 - .0028 clearance. A good machine shop is the key here, the cylinders are liners supported only by Orings (wet liners) and they can more around if the machinist is to aggressive with large cuts.
Exhausts Pipes & Cannisters
Generally one of the first places M/C owners go to increase power. Unfortunately, there's not much to choose from to really help the zg1000 that's available and affordable. Basically the options are mufflers or custom making your own pipe.
Mufflers - Used Cobras, Holeshots, Staintunes. Prices will range from a couple hundred used to 600 for the holeshots. Generally only good for 2-3 hp at best, and some noise. You'll accomplish the same thing by just drilling or punching out the baffle in your stock mufflers. Since the mufflers have no real meaningful effect on power, they don't require any re-jetting, though studying various dyno runs does show the slighly fre-er flow will slightly richen the main circuit.
Pipes - Jim Snyder pioneered what is most likely the best reasonable option for the concours - he used the downpipes from the stock pipe, and then brought 1-2 over behind the engine to meet with 3-4 and exit from one muffler. I have various dyno runs from Jim's bike, Shoodaben, and Daytona Mike's bike that all show the pipe to really help the torque in the midrange, with a pancake-flat torque curve. It is restrictive in the top end and limits peak HP, but not on a stock bore engine. This is the best way to go for a stock bore bike, or someone really wanting to have the most midrange they can get (all of us). I did a one - off 4-2-1 pipe on shoodaben, increasing the primary pipe size 1/8", joining 1-4 and 2-3 and having a single muffler. Other than sounding cool and saving weight, the dyno showed that it worked the essencially thesame as the stock pipe. It did, however, help the fuel economy - I could never get 40 mpg until I removed the stock pipe. still, it's a ton of work, and not at all cost effective. Bottom line - do a bafflectomy to your stock pipes, it's the most cost effective way to go.
Cams
Cams are typically the place a hotrodder goes right off. More is better, right? Not so when it comes to the connie. In fact, IMO, the stock cams are already to big, at least duration - wise - especially when coupled with to - large intake ports. GPZ900 and zx1000 cams will bolt in and pick up apx 10hp, but at the cost of lower rpm torque. In fact, stock cams will outpower the zx's until 7000 rpm, then the bigger cams pull ahead. if you don't spend the majority of time over 7000 rpm, your bike will actually be slower with the big cams (BTDT). Currently I have 2 different cam grinds, both with less duration than the stock cams. Both outpower the stock cams below 7000 rpm, my high lift grind will actually outpower the stock cams at peak power too, by apx 6 hp. Of course the advanced exhaust cam sprocket is the most cost effective way to go; it effectivly reduces the overlap and increases low rpm torque by more effective trapping of the incoming charge. Kind of a "poor mans" cam change.
I think it's worth mentioning that we should consider how we actually ride out connie's. I really don't know anyone who is trying to get maximum top speed, or 1/4 mile times from thier zg. everyone wants torque - the ability to twist the throttle without having to downshift or wind out the rpms to accellerate. This is where big cc's is king - but unless you're going to by a c-14, you'll have to optimise your zg's tuning. This is where I've always concentrated my efforts. when I say "hotrodding" I'm not meaning to make the bike a high rpm machine - that's not how we ride. Torque carries the day for our heavy shaft driven bikes.
Carbs
When the zx900 was originally intro'ed it had 34mm keihin cvk's. Those grew into 36mm on the zx1000, but were downsized to 32mm (along with smaller head pipes and smaller cams) when the engine was placed in the concours with a zg1000 designation. that leaves some interesting swaps avaialble. the 34's only had one cable, so I'd leave them alone. 36's are available from the zx1000's, gpz11's (95-96) zrx11's and 12's. All the bore spacings work on the zg head. The zrx carbs have idle cut valves like our 32's, so they can help eliminate the hard decel popping, but I run a set from the gpz, and even w/out the cut valves it's really not a problem. If you want to fit a set of 36's, use the head and intake manifolds from the gpz900 - interestingly they were produced in europe and I think australia til 2003, so you can actually order new rubber from Kawasaki. Of course custom jetting is the order of the day, and like the 32's it will vary depending on cam selection, but not so much on exhaust changes. Smaller cams need larger jets and richer needles. I personally think the 32's will feed 100 hp fine, so since you've got 'em use 'em. Y'all already know about the jetting.
