Pro424vt
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| posted on 26/7/19 at 12:22 PM |
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Running lean
First some info on the build. It's a duratec 2.0 with a 2.5 vvt head, vvt delete. Crower cams and valve springs, forged bottom end on a stock
crank. I'm running 40mm bike carbs from a 01 zx9r. Currently running it to about 8000 rpm but it gets really lean at the top end and I have 180
jets in it. No coughing or sputtering, no running issues at all other than the plugs are ghost white after 10 laps. I havent run an air cleaner to
this point and I can see a cloud of vapor outside the carbs outside the carbs at the end of the straights. Is this causing my lean condition or am I
way off on jetting?
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cliftyhanger
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| posted on 26/7/19 at 03:11 PM |
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You need to get to a rolling road experienced with bike carbs, or if you want to DIY fit a wideband sensor.
I think you may be lucky to still have a running engine, very easy to melt a piston with a lean mixture and too much advance.
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Pro424vt
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| posted on 26/7/19 at 03:27 PM |
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Think I'm mapped for about 26deg max advance at 80% load and 6800 rpm. I have a wide band I'm going to install this weekend. Just
wondering if I'm in the ball park for jetting.
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Dingz
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| posted on 26/7/19 at 08:20 PM |
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I think you may need bigger jets, 170 is about the start point on a pinto where you have less power. Spitting back through the carbs can be a symptom
of running lean but fuel stand-off may be due to short inlet tract, the mixture is rapidly beeing sucked into the engine, valve shuts and sends a
pulse backwards out of the carb. When a filter is on it’s not so noticeable.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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