73 Z1 with 29MM Smoothbores...weird problem

  • vintagerider
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11 Jul 2011 21:47 #462342 by vintagerider
73 Z1 with 29MM Smoothbores...weird problem was created by vintagerider
I have a 73 Z1 that I restored over the winter. It has a 10.5:1 1075 kit, stock cams, and 29mm smoothbores, also a vance and hines pro pipe. I disassembled the carbs and had the bodies ultrasonically cleaned (professionally) and put them back together with new jets, o rings, gaskets, needle and seats, and correctly set the float height of each carb. It has a 1.5 slide, 5dl31-3 needle, 17.5 pilots, and 117.5 mains. When the bike is cold and I first start riding on my test loop, it runs pretty decent. But by the time I'm riding for 10 minutes and about back to my house it will start to pop and carry on when I'm slightly on the gas or while decelerating. This is all while riding normal and shifting around 4K and cruising at 60-65. I'm not tuning it currently at full throttle or anything, just normal riding, very little stop and go. When I pull out at a stop sign it will bog and then go. The strange thing is while reading the plugs. #1 is lean, #2 is rich, #3 is lean and #4 is rich. All carbs are set up exactly the same. The coils control 1-4, and 2-3, so it doesn't seem ignition related. I switched the chokes around and no different, also took the pod filters off, no difference. Thinking possibly the needle/needle jet being worn? I checked compression as soon as the plugs were out and the engine is hot, and it's 150 accross the board. Carbs are also syncronized with gauges. I guess at this point I will just have to jet 2 carbs one way and the other 2 another. I don't want to do that, but not sure what else to do. Any ideas or if you had a similar experience let me know. Thanks

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  • mark1122
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12 Jul 2011 09:21 #462420 by mark1122
Replied by mark1122 on topic 73 Z1 with 29MM Smoothbores...weird problem
if it runs good cold and gets worse when hot, it is lean.
it could be an air leak by #2,4 intakes. start it up and spray wd40 around ALL of the intakes and listen for a change in rpm sound. if this is good, i would raise the needles 1 clip and test ride again.

76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.

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