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1986 VN750
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163 Posts
Discussion Starter #1
So I took my 86 VN750 out for a ride, rode about 35 minutes and stopped at the bank quick. Started it up again and the battery seemed a tad weak. I noticed that the cooling fan ran about 30 seconds after I turned off the ignition. Is it supposed to do that? Then I rode a few blocks and had to stop again.. (Girlfriend issues). Went to start her up and battery was so weak I had to bump start it. It's a brand new battery that was tested good by a shop. I rode about another 40 minutes and it ran fine. Left it sit for a few hours. Went to start it back up again and it cranked a couple times but again had to bump start it. I got about ten miles and it just died completely. The battery was just dead. Couldnt bump start it at all. I tested the stator and it has no ground and the voltage is good on all three legs. I followed the instructions on here perfectly. I tested the battery voltage when running at about 3000 RPM's and it's about 13.5 volts just where it should be if the R/R is working. So it seems that the charging system is fine.. Now the one thing I did notice is that the battery fully charged with the key off is about 12.5-12.65 Volts which is ok but as soon as I turn the key on (bike not started) the battery voltage drops to below 12 volts. About 11.85-11.95. Is this normal? I cant seem to figure out why the bike just died like that and Im afraid to ride it now.Ive cleaned all connections and searched through the wiring looking for grounds, etc... Any ideas would be helpfull. It all seems to be working just fine and Ive ridden it plenty and never had that problem before.
 

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Chasin' the blacktop
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1,498 Posts
I would load test the battery.
X2, 13.5 is a little low @ 3000 rpm, 14.6 is more common unless the battery is partially discharged.
 

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1986 VN750
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163 Posts
Discussion Starter #4
I had the battery load tested at a shop and they say its fine. Also, its difiicult to tell definitively what RPM the bike is at because the tach doesnt work... Im not sure what to do from here. The battery is a yuasa and I bought it brand new like 2 months ago..
 

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Banned
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2,190 Posts
Sounds like the bat is ok. Charging systems sounds low to me, but I do not know. I would check it. The manual states, 14-15v @ 4k rpms. I believe there is a comprehensive test in the verses. This would be my next step.
 

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NEVER TO OLD TO RIDE
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111 Posts
sounds like the charging system has a loose connection. unplug the connector from the regulator and check the connector and pins for burnt marks or corrision. also check the stator harness and connections same way. I installed a voltage gauge on mine so I can monitor battery and charging voltage.
 

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Chasin' the blacktop
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1,498 Posts
A simple thing to check would be your battery, R/R and starter connections but I agree with wmsonta, system voltage is a bit low which would cause both the hard starts and the bike dying.
 

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1986 VN750
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163 Posts
Discussion Starter #8
Other than the fact that I cant verify the RPM's due to the tach not working, the system voltage does seem low as you guys are saying. Ive seen a few posts on here about the headlight relay sucking the life out of system voltage and to reroute the blue wire to bypass the relay. Im gonna try that tonight and see if it makes a serious change. I will also look into adding a V meter.. Cant be too careful with a 1986 bike...
 

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1986 VN750
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163 Posts
Discussion Starter #9
sounds like the charging system has a loose connection. unplug the connector from the regulator and check the connector and pins for burnt marks or corrision. also check the stator harness and connections same way. I installed a voltage gauge on mine so I can monitor battery and charging voltage.
I have already gone through all the wiring and connections. Cleaned and checked for bad insulation. Plugs are all spotless and tight, no broken wires etc...One thing though is that the stator test procedure on here says that there should be bullet connectors on the 3 yellow wires from the stator before they plug into the R/R. Mine does not have these. The wires come out of the motor and go back into the harness then from there right to the R/R connector. Is this correct for an 86???
 

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Sparky!!!
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8,697 Posts
I have already gone through all the wiring and connections. Cleaned and checked for bad insulation. Plugs are all spotless and tight, no broken wires etc...One thing though is that the stator test procedure on here says that there should be bullet connectors on the 3 yellow wires from the stator before they plug into the R/R. Mine does not have these. The wires come out of the motor and go back into the harness then from there right to the R/R connector. Is this correct for an 86???
Some one could have soldered the writes together as that used to be common practice... But I think you are just overlooking the connectors... Physically fallow the writes out of the stator cover and back to the r/r... The bullet connectors should be located just in front of the left side cover

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1986 VN750
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163 Posts
Discussion Starter #11
Some one could have soldered the writes together as that used to be common practice... But I think you are just overlooking the connectors... Physically fallow the writes out of the stator cover and back to the r/r... The bullet connectors should be located just in front of the left side cover

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AHA! Previous owner had replaced the bullet connectors with crappy butt connectors. Cut those babies off and soldered followed up by heat shrink and taped it all back up. I'm getting over 14 volts at a medium rev now. About 14.35 to be exact and up to 14.55 at a higher rev. I cant seem to get the damn blue wire out to bypass the headlight relay... Any tips so as to not destroy the connector or the wire??
 

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AHA! Previous owner had replaced the bullet connectors with crappy butt connectors. Cut those babies off and soldered followed up by heat shrink and taped it all back up. I'm getting over 14 volts at a medium rev now. About 14.35 to be exact and up to 14.55 at a higher rev.
I love it, and it will last longer.

I cant seem to get the damn blue wire out to bypass the headlight relay... Any tips so as to not destroy the connector or the wire??
I am not familiar with this particular connector, but the first thing I usually try is a medium straightened paper clip from the connecter side. Not the wire side.
 

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Sparky!!!
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8,697 Posts
If the headlight isn't coming on until the engine sounds over, leave it.. The blue write bypass only bypasses the relay and make a hard starting bike worse because the headlight is constantly on while the engine is trying to draw as much power as it can to start

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1986 VN750
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163 Posts
Discussion Starter #14
FML

Just when I think all is good.. I soldered up the stator wires and test drove the bike. It worked fine for a few miles, brought it home and turned it off. I checked the battery voltage with the bike off to be safe and it was about 12.75. Good... I decided to start her up and double check the idle voltage. I pressed the start button and BOOM everything went black. Lights out, starter stopped cranking. (it only cranked twice) Then the lights came back on, but the power just drained completely in seconds. There's obviously an intermittent ground somewhere. Any ideas on how to find it?? Is the puck known for this kinda crap? I havent opened it up yet. Im thinking its gotta be somewhere by the headlight/instrument cluster. I had the headlight housing open and went through all the wiring and everything is nice and clean. I went through all the wiring from the tank back and all is clean.. Ugh any advice would be helpful.
 

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1986 VN750
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163 Posts
Discussion Starter #17
grounds and positive battery cable are tight and test fine. Seems that the wiring going into the puck kills the bike when wiggled. I recharged the battery, started right up, idled and started wiggling wires. Every time I touch the wiring under the dash/instrument cluster... boom out goes the power... So puck surgery it is I guess... Ive seen people on here describe disassembly and repair so I'll tackle that Monday after my son goes back to his Mom's...
 

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3,353 Posts
can you isolate which bundle of wires is the culprit?

Just a thought, but in the headlight bucket is a set of "accessory wires" that are powered even when the key is in the off position and out of the ignition....Back/Yellow(ground) and White/bLue(+12V) that have a rubberized covering over the ends (maybe the 12V lead end is touching the bucket housing or something)
It might be that they are somehow shorting out when you move the wire harness..... as in moving the handlebars or something.

It might be worth opening up the headlight bucket and inspecting the wires/connections inside as well as where the harness enters the bucket. The bucket is metal and the edges are not blunt, so the harness might be digging into the housing and chaffing the wire harness.
 

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1986 VN750
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163 Posts
Discussion Starter #19
can you isolate which bundle of wires is the culprit?

Just a thought, but in the headlight bucket is a set of "accessory wires" that are powered even when the key is in the off position and out of the ignition....Back/Yellow(ground) and White/bLue(+12V) that have a rubberized covering over the ends (maybe the 12V lead end is touching the bucket housing or something)
It might be that they are somehow shorting out when you move the wire harness..... as in moving the handlebars or something.

It might be worth opening up the headlight bucket and inspecting the wires/connections inside as well as where the harness enters the bucket. The bucket is metal and the edges are not blunt, so the harness might be digging into the housing and chaffing the wire harness.
I'll check that out today while I'm digging through the dash wiring. I'm pretty sure it's the ignition switch wiring causing the issues. I'm going to pull it all apart and double check it all though. Thank you guys!
 

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1986 VN750
Joined
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163 Posts
Discussion Starter #20
can you isolate which bundle of wires is the culprit?

Just a thought, but in the headlight bucket is a set of "accessory wires" that are powered even when the key is in the off position and out of the ignition....Back/Yellow(ground) and White/bLue(+12V) that have a rubberized covering over the ends (maybe the 12V lead end is touching the bucket housing or something)
It might be that they are somehow shorting out when you move the wire harness..... as in moving the handlebars or something.

It might be worth opening up the headlight bucket and inspecting the wires/connections inside as well as where the harness enters the bucket. The bucket is metal and the edges are not blunt, so the harness might be digging into the housing and chaffing the wire harness.
Man you're good KC. The aux 12v wire was outside theheadlight housing being pinched in the collar on the fork rotor thing. I shrink tubed the connector and shoved it in the headlight housing. Bike seems to be ok but from starting it 4 or 5 times to test, I ran the battery down. Its a new battery. with a full charge, should it be dying like that after starting 4 or 5 times? it only needs to crank like twice to start. I have it tuned up nice. Just wanna make sure because I had to charge the damn thing again and once again Im afraid theres something else wrong that will leave me stranded. Obviously starting the bike and idling it will run down the battery right? Thanks again..
 
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