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Finally got my carbs/intake situation fully set up perfectly 03 Jun 2020 12:55 #827228

  • gavroyer
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After much fiddling and playing with things to get everything working fully properly, I finally have gotten my KZ440's carbs working perfectly. Bike starts up immediately on the starter or with the kicker, and the idle is nice and even. Mixture screws are 2.75 turns out from fully seated, so a tad richer than stock but still nicely within the spec (and much closer than they were before I cleaned them out last night).

A couple of weeks ago I'd had my bike running great, and had just synced the carbs and adjusted the idle mixture. The mixture screws needed to be about 3.5 turns out for the best idle, so that was a bit ehhhhh, but otherwise everything was looking great. Then a couple days later, we got a massive rain storm. My bike doesn't like being massively soaked; I think something in the ignition system is getting too wet and shorting out somewhere. After that I noticed an odd hesitation on application of the throttle, like one cylinder wasn't firing for the first few cycles after rolling on hard. I took a look at the plugs and the left-hand side plug was very white, looking way lean, but the other was fine. I adjusted the mixture out another turn or so (putting me pretty solidly out of spec) and the hesitation went away. However, I wasn't happy with the mixture screws being so far out, and the hot-starting in this state was miserable.

Last night I received a rebuild kit from Z1, so I pulled the carbs off and cleaned/replaced all the seals and passageways out very thoroughly with some carb cleaner. I got everything put back together and the bike fired right up on the choke, but I didn't want to check the mixture as it was 10pm and I didn't want to upset the neighbours, so I went to bed for the night.

This morning I got up and did a quick idle-drop tune and to my surprise, the ideal idle came with the mixture screws just 2.75 turns out, just a hair richer than the stock 2.5. I was able to maintain a relatively smooth, stable idle around 500 RPM, too, which before would've been hard to accomplish without the engine dying (I did then reset the idle for 1200 RPM, which is the spec). The throttle response is great, idle comes down acceptably fast, and the firing is nice and even. Plus the hot-start performance is great again.

1980 KZ440-A1 LTD

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