I have had a GS700 for about a year now. It was a great deal on craigslist, only $1000 with <9000 original miles. It had a 4-into-1 header with a Vance & Hines slip on and 4 pod filters. I noticed the bike yawned out pretty badly and suspected they never rejetted the carbs. When I went to take them apart there were all sorts of stripped screws and every single pilot screw had to be drilled out. Unfortunately, one of the screws didn't cooperate and I am left with a 4th carburetor with a stuck tip and eaten up threads. Garbage. (Unless you all can help me fix that?).
So I went on ebay, and looked up the part number of the carb I needed, lo and behold I found one, still in its original packaging, new. I got it in the mail, swapped out the jets, but noticed it looked a little different. It has a larger diameter slide and a larger diameter engine-side outlet (but small enough to squeeze into the boots with significant help from a jack-strap). The choke linkage, float bowl tubes, and just about everything else was a perfect fit, so I figured I would roll with it.
I didn't have a chance to ride it much after this, as it was vandalized shortly after, TWICE, and I had no time to fix it. A couple months went by and I knew I had to clean the carbs when it didn't start. I cleaned the carbs and checked the float levels just to be sure, since it was about the only thing I didn't do when I rebuilt them, and they were all way low (that is, they allowed in too much fuel), including the brand new one which I never touched (weird, huh?). So, I adjusted all of them up to 22.4 mm (letting in less fuel), measuring from the gasket surface to the lower "step" of the float, with the floats sitting on the needle, no compressed spring.
I adjusted the valves (which required removing the coils, I may have mixed some wire up). I also replaced the spark plugs as they were pretty fouled from running on choke for too long. The bike starts up (with some difficulty), and idles erratically (seems like a hanging idle), but still holds an idle. I took it for a spin just to see how it ran, and it had very little power. It felt like it was only running on 2 cylinders. If I gave it any more than 1/2 throttle, nothing. In fact, more throttle made it backfire even worse. It could hardly keep up 45 mph on a slight incline, and definitely wouldn't exceed 55 regardless. Where do you all think I should look? What might cause the 1/2 to WOT no-power backfiring?
I should note that I have ridden it while it ran reasonably well, with the current jetting, shims, drilled slides, pod filters and exhaust. It had plenty of power. Also note that the carb has been recently cleaned, and I am using high-octane fuel, no ethanol, with seafoam. Any help is much appreciated.
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