Warm start issues - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 11 (permalink) Old 09-14-2017, 09:04 PM Thread Starter
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Warm start issues

So after I finally rebuilt my 750, and finally started to learn riding, I'm having issues with the warm starts. When I first started it cold, started fine, only needed slight choke, and idled ok. Cut ahead, I shut it off, and it cranked, but took a long while to start. Finally, when it did, the idle RPM was stuck at 3-4000 and wouldn't drop, even when revving. So I adjusted the idle control knob, got the RPM down to 1100, and now when it shuts off, it needs more of the choke lever out, and still starts hard (though easier), and needs some throttle when cranking. The idle was 1500 this time, so I adjusted it again to 1100. So what can be the cause of these hard starts when warmed up?
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post #2 of 11 (permalink) Old 09-14-2017, 09:37 PM
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does it backfire loudly when trying to start? if so,look into an AGM battery.also look up the pick-up coil mod

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post #3 of 11 (permalink) Old 09-14-2017, 09:45 PM Thread Starter
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It'll occasionally make a (small?) pop, I try to let it sit between longer cranks to avoid flooding
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post #4 of 11 (permalink) Old 09-14-2017, 10:07 PM Thread Starter
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Another question, how much movement should the choke plungers on the carburetor have? I can put my choke lever all the way forward/choke off position, but I can push the plunger in more with my hand on the carburetor. Is this normal?
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post #5 of 11 (permalink) Old 09-14-2017, 10:08 PM
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Mine never will hot start with the throttle open, even have to choke it sometimes after just a few minutes being parked. If I open the throttle at all it just backfires.

Sounds like a mix of some flooding maybe, with an air leak. Check the carb boot clamps (air leak) and check the petcock vacuum line to make sure there's no gas in it (flooding front cylinder).

AGM battery makes for better starts, and the Two-Wire Mod can help with hot starts also. Both help with voltage.

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post #6 of 11 (permalink) Old 09-15-2017, 11:27 AM
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So now that you mention it, when I replaced my petcock with the tw200, I don't think I had any hot start issues again. It ran better too. So maybe that vacuum is affected by the heat and that changes pressure etc. ? It's a $15 something to try.

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post #7 of 11 (permalink) Old 09-15-2017, 02:33 PM
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So now that you mention it, when I replaced my petcock with the tw200, I don't think I had any hot start issues again. It ran better too. So maybe that vacuum is affected by the heat and that changes pressure etc. ? It's a $15 something to try.
When the petcock leaks gas through the vacuum line, it richens the front cylinder while running. But the bigger problem is after shutdown, gas still flows through the vac line, which fills the front cylinder (flooded) and gas ends up in the oil if it's parked long enough.

I'm not sure even turning the petcock off, stops all the flow through a leaking diaphragm. Think I could still ruin an oil change just parked with the petcock off for a week.

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post #8 of 11 (permalink) Old 09-15-2017, 08:58 PM Thread Starter
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My issue seems to be tracing back to the fact that the choke won't fully close, leading more gas into the cylinder. I have a thread opened about that.

https://www.vn750.com/forum/22-carbs-...tuck-open.html
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post #9 of 11 (permalink) Old 09-15-2017, 09:35 PM
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Don't use any throttle when hot starting.
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post #10 of 11 (permalink) Old 09-17-2017, 06:34 PM
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I don't use any throttle when hot either,I just touch or bump the start button hot or cold with choke.
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