I recently bought a 92 750sx and it has a CDK II 38mm carb in it. It has a factory pipe and K&N air filter plus some other fun stuff unrelated to the engine. When I bought it, it would absolutely rocket out of the hole at about 1/3 throttle but if you stayed above 1/3 throttle for more than a second or two it would bog down and die. The transition was always very smooth but it wouldn't last. Also if I rode it continously for a few minutes at low throttle it would get twitchy and/or die.
I decided that a carb rebuild was in order so I got one from SBTontheweb (very poor quality kit IMHO). No carb to intake manifold gasket, not all the o-rings were included, and there were parts that didn't fit my carb left over. Anyway, after the rebuild it wouldn't run at all with the new pop off spring. I put the old spring back in and it ran better but still much worse than before. Now I can get it to idle but the rpms systematically go up and down to what sounds like about 700-1000 rpms. I used RTV to seal the carb to the intake manifold so I'm wondering if that's the cause of that problem. At the same time I can't tune the carb to save my life. The best I ever got it tuned, it would ease through the rpms if I did it slowly and would top out but then it would fall back down seconds later. If I rode it slowly with that setup it would go normal and then out of nowhere, it would practically throw me off the back of the ski when it went WOT without me changing throttle position.
I can't figure this out to save my life. I'm wondering if I'm just missing something with the pop off springs or needle settings or whether the kit and a leak between carb and intake could be causing all of this.
I decided that a carb rebuild was in order so I got one from SBTontheweb (very poor quality kit IMHO). No carb to intake manifold gasket, not all the o-rings were included, and there were parts that didn't fit my carb left over. Anyway, after the rebuild it wouldn't run at all with the new pop off spring. I put the old spring back in and it ran better but still much worse than before. Now I can get it to idle but the rpms systematically go up and down to what sounds like about 700-1000 rpms. I used RTV to seal the carb to the intake manifold so I'm wondering if that's the cause of that problem. At the same time I can't tune the carb to save my life. The best I ever got it tuned, it would ease through the rpms if I did it slowly and would top out but then it would fall back down seconds later. If I rode it slowly with that setup it would go normal and then out of nowhere, it would practically throw me off the back of the ski when it went WOT without me changing throttle position.
I can't figure this out to save my life. I'm wondering if I'm just missing something with the pop off springs or needle settings or whether the kit and a leak between carb and intake could be causing all of this.
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