Another angle on the hot start issue? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 09-10-2014, 10:57 PM Thread Starter
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Another angle on the hot start issue?

Hey everyone- fyi I'm on an '04 VN750 with 42,000 miles. Last year when I bought it I was having the same hot start issue everyone on here complains about. A set of NGK iridium plugs and a MF battery later and presto chango, hot start problem is gone. A year goes by, and suddenly this summer the issue has come back. I pulled the spark plugs and cleaned them up, they seem just fine. I have also done a partial pickup coil mod (when I gapped them to .020 as recommended I got a nasty squealing sound coming from them when I fired up the engine, so I backed it off to about .025, I may revisit the mod later). The pickup coil mod seems to have helped a bit, but hasn't gotten rid of it.

When I was testing out the pickup coil mod, I came across an interesting finding. The bike had zero problems restarting until the PRECISE MOMENT the radiator fan kicked on. Once that happened I had to let the bike sit 15-20 minutes before it would fire up again. So, here's my theory and what I've done about it so far:

I think that the battery is being barely undercharged, and when the radiator kicks on that puts a load demand on the battery that's just slightly higher than the charge rate. This would be a cumulative effect, slowly draining the power every time the radiator came on over the past year, until a couple of weeks ago that it became drained just enough for it to begin affecting restarting again. Alternatively, the charging system is fine but for some reason the radiator is drawing more current than it should be. To test this, I picked up a battery tender and plugged it into the bike today. As soon as I plugged it in I got a red light on the tender unit, indicating the battery was less than 80% charged. 20 minutes later its a blinking green, and an hour after that solid green, indicating full charge.

I then fired up the bike and let it sit until the engine warmed to the point of triggering the radiator fan. Unfortunately recharging the battery wasn't quite enough to eliminate the problem completely (however, it wasn't as bad as before, it hesitated to start but didn't need to sit as long). I pulled the key out of the ignition and plugged the battery tender back in and, lo and behold, the red light is on again. Somehow this battery is getting drained and quickly, and I believe the radiator fan is the culprit. Or maybe I'm talking out my a**

Thoughts, suggestions on where to go from here? To my knowledge there have been no other mods to the stator or regulator/rectifier, but I can't be certain as I am not the original owner. I also have only limited tools and mechanical experience, so I'm hesitant to get too crazy with mods here.

Last edited by bluguitar89; 09-10-2014 at 11:25 PM.
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post #2 of 10 (permalink) Old 09-10-2014, 11:37 PM Thread Starter
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Edit- another thought just occurred to me. A few weeks ago I had the radiator partially detached to make room for mounting a set of kuryakyn highway pegs. I never messed with any of the wiring, but would it be possible that I accidentally caused a short somewhere in there that could account for this behavior? The time frame roughly lines up , but I can't say for sure. I know the hot start issue came back after I mounted the pegs but perhaps not immediately- could just be a coincidence. However, I could see how a crossed wire wouldn't have any affect until the switch comes on to activate the circuit.
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post #3 of 10 (permalink) Old 09-11-2014, 03:15 PM
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In order to validate your theory, we need to establish 2 things first:

1 - is the charging system working properly? (see the sticky in electrical for testing the whole system)
2 - is the battery indeed good? (load tested)

The stock system will indeed put a slight drain when the fan runs at idle, but this should not effect hot starts if everything is up to snuff.

I found on my 06 that the hot start issue went away with the pickup coil mod.....and this was with stock charging system and a wet cell battery.
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post #4 of 10 (permalink) Old 09-11-2014, 03:28 PM
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Quote:
Originally Posted by kc2dgq View Post
In order to validate your theory, we need to establish 2 things first:

1 - is the charging system working properly? (see the sticky in electrical for testing the whole system)
2 - is the battery indeed good? (load tested)

The stock system will indeed put a slight drain when the fan runs at idle, but this should not effect hot starts if everything is up to snuff.

I found on my 06 that the hot start issue went away with the pickup coil mod.....and this was with stock charging system and a wet cell battery.
+1

ditto on my 05, except it has an AGM battery

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post #5 of 10 (permalink) Old 09-11-2014, 05:01 PM Thread Starter
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I'll borrow a proper meter from my father in law and get back to you on that, in the mean time I think I'll revisit the pickup coil mod. Any thoughts on what could cause the squeaking/squealing sound I heard coming from the coils when I did it the first time? I was afraid the electrodes were actually making physical contact for some reason...
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post #6 of 10 (permalink) Old 09-11-2014, 05:59 PM
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if they are too close (would have to be touching the flywheel) it could squeal/squeak I imagine.

when I gapped mine down to 0.020 inches I made sure I had the magnets on the flywheel aligned with the pickup coils. I am not sure, but they may stick out of the flywheel slightly, and if you gap at the wrong point on the flywheel, you could end up too close

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post #7 of 10 (permalink) Old 09-12-2014, 05:00 PM
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Quote:
Originally Posted by michiganteddybear View Post
if they are too close (would have to be touching the flywheel) it could squeal/squeak I imagine.

when I gapped mine down to 0.020 inches I made sure I had the magnets on the flywheel aligned with the pickup coils. I am not sure, but they may stick out of the flywheel slightly, and if you gap at the wrong point on the flywheel, you could end up too close
X2

rotate the center hub untill the magnets are aligned with the pickups. Also check tha gap AFTER you tighten since they can move with the screws being turned.
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post #8 of 10 (permalink) Old 09-12-2014, 05:35 PM
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Quote:
Originally Posted by michiganteddybear View Post
if they are too close (would have to be touching the flywheel) it could squeal/squeak I imagine.

when I gapped mine down to 0.020 inches I made sure I had the magnets on the flywheel aligned with the pickup coils. I am not sure, but they may stick out of the flywheel slightly, and if you gap at the wrong point on the flywheel, you could end up too close
Quote:
Originally Posted by kc2dgq View Post
X2

rotate the center hub untill the magnets are aligned with the pickups. Also check tha gap AFTER you tighten since they can move with the screws being turned.
lets X3 that KC (the double check part)

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post #9 of 10 (permalink) Old 09-12-2014, 09:17 PM
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nobody ever talks about the ignition coil mod anymore. thats the only mod that cured the hot start issue for me.


99 vn750A15
stator mod and r/r mod
ignition coil mod
ignitor power circuit and ground circuit mod
ear shave rejet 142/42 plus .040 shimmed
vance and hines exhaust no baffles
custom paint
volt meter
petcock mod
new backrest and pad (no pic yet)
cooling fan cut off switch mod
jbm carb diaphrams (must have)
mcct mod
pickup coil mod
AGM Battery

did all the mods and repair work and custom paint myself. except exhaust.
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post #10 of 10 (permalink) Old 09-13-2014, 01:44 AM Thread Starter
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Ignition coil mod?
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