Warm engine will not start - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 13 (permalink) Old 09-07-2018, 12:50 PM Thread Starter
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Warm engine will not start

Help I have a problem.
When my engine is cold, it is very easy to start and drive. The engine also run smootly both in idle and speed. But when the engine is warm and I stop it for a few minuts, it is almost impossible to start it again. I can turn the starter engine 15-20 seconds without the engine will start (sometime it will start). If I wait 40 - 45 minutes, I can start it again without problem.
I have try to use the choker, but that does’t help.
The spark plugs is new and they looks great after driving a long distance.
I have also check the ignition coal; all four makes a nice blue spark over 10 milimeters.
I have try to remove the airfilter, but that does’t help.
Finaly the cabs are newly synchronized but, that was before I discovered a crack in one of intake rubber boots. Both of the rubber boots have been change now, so maybe the synchronizing is not so good anymore, if the crack was there, during the synchronizing. But the engine run smootly, as I wrote.
Any ideas would bee mostly welcome.
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post #2 of 13 (permalink) Old 09-07-2018, 01:05 PM
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Your battery is the likely cause. Is it a fairly new AGM ? If not, it should be .....

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post #3 of 13 (permalink) Old 09-07-2018, 01:07 PM
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Search the forum for 'pickup coil mod'.

1992 US-nonCA * tuxedo mod * r/r relocated

Vulcan slang for newcomers
Service Manual Download
Wiring Diagram + annotations * still undergoing revisions, but still more useful than the generic one. Let me know if you find mistakes or think something additional should be added
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post #4 of 13 (permalink) Old 09-07-2018, 02:26 PM Thread Starter
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Quote:
Originally Posted by Knifemaker View Post
Your battery is the likely cause. Is it a fairly new AGM ? If not, it should be .....
I have a brand new batteri
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post #5 of 13 (permalink) Old 09-07-2018, 04:38 PM
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Quote:
Originally Posted by Preben59 View Post
I have a brand new batteri
Is it a common wet cell? Batteries can go bad, even new ones..

How are you trying to start it when warm? (Removing the airfilter of using the choke wouldn't help) The starter should only run 3 seconds for each try. If your holding it for 20 seconds you're straining the battery.

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post #6 of 13 (permalink) Old 09-08-2018, 02:09 AM Thread Starter
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Yes it is a acid batteri.
I hold the starter in 5-8 second severel time
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post #7 of 13 (permalink) Old 09-08-2018, 08:28 AM
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as already mentioned, the best battery for these bikes are AGM type lead acid batteries.. they dont have any way to add water/electrolyte after manufacture, as they are sealed. the standard lead acid battery has fill caps for topping off electrolyte/water.

also already mentioned is the pickup coil mod. to the best of my knowledge, everyone who has done it, no longer has warm/hot start issues.

the pickup coils from factory are set a country mile from the flywheel/magnets.. after mod, they are set to .020". I think on mine the coils where set to about .060" from factory, which is huge for a magnetic pickup gap.

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post #8 of 13 (permalink) Old 09-08-2018, 10:12 AM Thread Starter
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Very interesting and usefull. I will try to modify the pickup coil and returne the result 👌 Thanks a lot
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post #9 of 13 (permalink) Old 09-09-2018, 12:09 PM Thread Starter
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Hi everyone
I have now mod. my pickup coil to 0.02”. THAT HELPS A LOT 😁 Thanks to you all friends
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post #10 of 13 (permalink) Old 09-11-2018, 08:53 AM
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Quote:
Originally Posted by Preben59 View Post
Help I have a problem.
When my engine is cold, it is very easy to start and drive. The engine also run smootly both in idle and speed. But when the engine is warm and I stop it for a few minuts, it is almost impossible to start it again. I can turn the starter engine 15-20 seconds without the engine will start (sometime it will start). If I wait 40 - 45 minutes, I can start it again without problem.
I have try to use the choker, but that does’t help.
The spark plugs is new and they looks great after driving a long distance.
I have also check the ignition coal; all four makes a nice blue spark over 10 milimeters.
I have try to remove the airfilter, but that does’t help.
Finaly the cabs are newly synchronized but, that was before I discovered a crack in one of intake rubber boots. Both of the rubber boots have been change now, so maybe the synchronizing is not so good anymore, if the crack was there, during the synchronizing. But the engine run smootly, as I wrote.
Any ideas would bee mostly welcome.
When the engine is hot, no choke and 2/3 of full throttle. This always works with my 750 Vulcan.
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