Kawasaki VN750 Forum banner
1 - 11 of 11 Posts

· Registered
Joined
·
148 Posts
Discussion Starter · #1 ·
I thought this was resolved with a new battery but it's not. I believe it is electrical. The primary on the coils is .2 ohms high on each coil and the stator appears to be functioning normally except the DC charging voltage occasionally drops to below 10 momentarily before rising back up to normal. The r/r passes the diode test and the stator resistance readings are normal. Am I looking at the stator, r/r, or the coils as the likely culprit?
 

· Registered
Joined
·
10,830 Posts
Happen to have a voltmeter on the dash? And does the stumble coincide with the voltage drop?

Any backfire if you add throttle during the stumble and voltage drop?

Asking because mine was doing this on my last couple of rides.

Only thing I found for sure is the front right spark plug cap is arcing on the throttle cables. (probably not related to the voltage drop)

I guess I would check the AC voltage on the stator before blaming it.

Haven't figured this voltage drop out yet. Mine already has the Two Wire mod, does yours? Any other electrical mods?
 

· Registered
Joined
·
148 Posts
Discussion Starter · #3 ·
I have the blue wire and two wire on mine. The voltage drop is while just idling. On the AC side, I did not notice it when I last checked but that was about a week ago. If the voltage drop is real, I would assume it means a failed r/r which would surprise me since those MOSFET style ones seem like they're pretty bulletproof
 

· Registered
Joined
·
10,830 Posts
Ok, my voltage drop, with stumble, was always at light steady cruise around 3000 rpm.

The only thing you didn't mention testing is the ohms on the pickup coils.

The .2 ohms high on the ign coils, do you know what setting the meter was on?

There's also plug wires and plug caps, you could check the spark for color and strength, and watch it running in the dark to see if there's any arcing. Water sprayed from a bottle can help . Also make sure wire connections on the ign coils are tight.

There should be an ohm spec in the manual for the plug caps, those have a resistor built in.
 

· Registered
Joined
·
412 Posts
I do not know much about electronics or how many of the components work. I have read how to test them but it isn't something that comes to me naturally. However, wonky voltage issues can sometimes be caused by a bad ground somewhere in the system. I would go though the whole wiring system and clean up every ground. It can't hurt and costs nothing but time and energy.

Cleaning grounding points should almost be part of a regular maintenance routine. You don't have to do it every o change but every couple of years or so is a good idea. Corrosion buildup and resistance can occur that is invisible to the eye and is very often overlooked. Cleaning the terminal connections for the battery (getting the dull lead to be all shiny and pretty) gives you an idea of how this issue looks because it is easy to see on the lead terminals but the reality is the rest of the system is also susceptible to problems over time. Bare metal and dielectric grease is your friend when it comes to keeping the electrical system in shape.

I don't know if it is related to your problem or not but is you have a MOSFET and not the stock type regulator/rectifier you are correct in that they do not often fail. In fact many guys install used ones to begin with.
 

· Registered
Joined
·
148 Posts
Discussion Starter · #7 ·
Sorry I haven't been checking in much. I measured resistance on the primary at regular ohm setting and it was .2 higher than the book spec range on each coil. On the secondary I left the spark plug caps on. They're 5k ohms each and the way I see it, the overall resistance is important there but they are well within spec on both coils. I forgot to mention the AC voltage did not seem to experience the same voltage drop that the DC does at the battery and sits at a steady 40ish volts at some revs. Bad ground could be possible. Spock if you're open to it, I can give you a call about it to discuss. Knowing someone else may benefit from my fixing this bike will give me the motivation to step away from my 9 others bikes. Mine stumbles around 3-4k but levels out to normal at around 5k and up. It feels electrical to me but maybe that's where the pilot jets switch over to the mains. I did recently do the ear shave but these symptoms are more recent than that
 

· Registered
Joined
·
148 Posts
Discussion Starter · #8 ·
Misread your statement. Pickup coil is a good thing to check. That's a good spot to check since my pickup coil is very janky. It's a coil soldered in from a vulcan 1500 (resistance was the same) since my only one broke at the connection point and I'm not skilled enough to solder that reliably. That setup has been serving me well for a good number of miles though
 

· Registered
Joined
·
148 Posts
Discussion Starter · #9 ·
Green thanks for the suggestion. I've cleaned connections in the past but didn't have dielectric grease. It's one of those things we all know we should do but put it off. I will take your words and start being more proactive with all my bikes as part of that "while I'm in there" ideology. Decided to throw in some additive carb cleaner and top up the gas. I'm now realizing how long ago it was since the bike was laid up for the shaft replacement. I feel very stupid because this may just be a case of bad gas. Never had that happen before on any of my bikes. There's still a noticeable stumble but it is not nearly a bad a it was before. I'll side through the rest of this tank and see how it goes with throwing some additive in with every refuel for a bit. I'll check back in if it's the solution I'm looking for. It still doesn't explain the DC voltage thing but that could be the cheap harbor freight meter
 
  • Like
Reactions: Spockster

· Registered
Joined
·
10,830 Posts
Keep us posted! If it comes back, we might have to revisit voltage, and might need the dash mounted voltmeter.. I initially thought about fuel but didn't want to introduce that just yet since you were thinking electrical.

Just talked to Chris on the phone. This guy is definitely a rider, ten bikes, 2500-3700 mile rides pretty often, just hop on and go. He's been holding back on ride reports though. ;) Good talking to ya!

Said he's got a gallon of Lucas fuel treatment, and he definitely has the tanks to put it in.
 

· Registered
Joined
·
907 Posts
This sounds like fuel to me.

When I was testing a new ignition controller, I did a bunch of testing. I always had a bit of a notch in throttle response around 4k. I think this is the transition to main jets. I recently had one clogged pilot jet. It only idled on one cylinder, but cleaned up above 4k or with heavier throttle.

Has it gotten colder where you live? Perhaps after the ear shave, you were on lean side of good and the cold air pushed you into lean?

If it's electrical, it should get worse with more throttle and more RPM, as it takes more power to ignite, and the spark happens more often. If worse with both throttle and RPM, then the problem is likely before or at the ignition coil. (Not enough voltage getting to the coil primary). If only worse with throttle and relatively unaffected by RPM, the problem is likely at or after the coil (plug or wire) as the rate of spark won't really affect this.

I had a leaky plug wire that would only arc under throttle, same at all RPMs. Later I had corroded charging wires and it would misfire just off idle and by red line but was fine in between. Low charging voltage.
 
1 - 11 of 11 Posts
Top