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Electrical Fixes

2864 Views 4 Replies 3 Participants Last post by  rdrabing
I’m an Electrical Engineer specializing in power supplies, and I have owned a VN750 since 1992 (1993 model). I have almost 60,000 miles on it. I’m very happy with the bike except for the electrical system. It is the worst designed motorcycle that I have ever seen in that area. Almost nothing has been done right! I had to rewire, and redesign, the motorcycle to get the kind of performance that I think I should have had out of the box.

I see two major complaints, in general, about the electrical systems. Not only are these complaints on this forum, but I have known others, personally, with the same bike and with the same problems. I believe that I can help many of you.

First, I am on my third stator - and it has failed. Every failure has been a short between the windings and the laminations, which are connected to the engine case and the frame. This is a most annoying failure for at least two reasons. One, it results in poor battery charging which can leave you at the roadside in the worst places. And, two, the poor design of the Engine mounting means that you have to essentially remove the engine from the frame to get the cover off for access. (I realize that a full removal is not necessary.)

This is so much time and work again, that I am considering cutting the frame for future access. I certainly wouldn’t recommend this if you are concerned about resale value, and, of course, the frame must be repaired properly! For this last failure, I built a power converter that will allow for a single short in the stator. I can’t recommend this either since I spent way too much time on that design, but, at least, I was inside the house most of the time. Also, it is likely that a second short will develop, in time, and kill this idea.

One thing I now know for sure – the Kawasaki stator is a waste of money. For about $300, you are lucky if you can get a couple of years out of it! Electrexworld in the UK offers a replacement that is about 1/3 the price, and it seems like it can’t be any worse! (I haven’t purchased one yet from them.) Because of the poor reliability, however, the cost of the stator is not the major issue. I’ve also added a LED circuit to tell me when the battery is being charged. It’s a little tricky because the voltage drops in the wiring lower the voltage significantly near the handlebars. You have to compensate for that, and if the headlight should quit, the compensation would be all wrong.

Incidentally, should you get stuck by the roadside with what seems like a bad battery, it might be possible to get going again if you disconnect the headlight. Let’s assume you can get started by pushing, or rolling down a small hill. The headlight may remove enough load for the remaining stator windings to run everything else. It worked for me.

The biggest complaint seems to be the poor starting. Yes, a good battery can help, but the real problem is the wiring drops and poor tolerance for low voltage in the ignition circuit. My first approach was to build a boost circuit for the voltage to the ignition circuitry. It would keep up the voltage, even when the battery was cranking near 8 volts. The starting was nothing short of miraculous! A short stab at the start button would immediately bring the engine to life. Battery quality was unimportant as long as it could turn the engine over. What wear and tear I had previously given to the poor, abused, starter motor was not going to increase any more.

This seemed a perfect solution until I later discovered that there was a more fundamental problem, and much easier to fix. I lost a connection to my boost circuit, and while I was contemplating the situation, I began to probe around some more. The wiring on the motorcycle is designed with rather minimum wire size. I assume this is to save money, however, as I have observed on this site, there is a tendency for the wiring to overheat and burn in a few areas. I too, have had burned connectors in the stator wires.

The battery voltage is wired through the ignition switch and back to the ignition circuits. With all the loads, including the headlight, there is considerable drop by the time it gets to the ignition circuitry. The solution was actually quite simple. I purchased an automobile relay, available through Radio Shack, and others, and inserted it between the battery and the ignition wiring. (You need at least 10 amp contacts on the relay.) The relay wiring must include the primary wiring of the high voltage coils, one of which, is under the gas tank. You must remove the wire connected from this front coil to the ignition switch. Then wire the front coil to the relay contacts along with the other high voltage coil near the battery. Additionally, also wire the ignition circuit to this same contact. Use some heavy gauge wire to do this - #14 AWG would be good.

Now connect the wire that was tied to the ignition switch to the relay coil, and tie the other side of the relay coil to frame, or chassis ground. You don’t need heavy wire for this connection, but make sure it is a good quality stranded hook-up wire, and it is best to use Teflon insulation, if you can get it. This will avoid burn-through from any hot sources, and also helps with chafing. There is plenty of room for the relay, close to the battery.

I can’t be sure that this later solution by itself will cure all starting problems. I have a maintenance free battery now, and the boost circuit doesn’t seem to provide any advantage in starting when added to this change. I suggest getting a wiring diagram with color codes before you start. Know what you are going to do before you start, because wiring errors could cause significant damage. Good practice would be to disconnect the battery, and check everything with an ohmmeter, or continuity tester. I would like to know how well this works if anyone else tries this modification.
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Hello i'm a new owner of a vn750 and it seems like you say..
in fact it seems that there is no sufficient voltage on tci box when the starter turn, i've already replace the starter cable by a new one , home made and the starter is better now but it's still not sufficent

Could you explain more tthe mods you have done on the ignition side (relay etc)
with drawings and pictures:smiley_th
seems to be easier to try if i've just to follow you :D

thanks a lot
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Certainly glad to have another electrical engineer trying to find solutions for our bike!
I am on my second stator. stator failure is not unique to the VN750, what is unique about it though and escalates the problem is it requires an engine pull to replace. We have considered the frame modification and have not come up withe a good left sub-frame redesign yet. There is however a stator cover modification that eliminates the engine pull.
This can be found at http://www.tocmanufacturing.com/Side_Cover_mod.htm
I am not sold on the Electrex stator being a better stator and opted to put a used stator in along with the side cover modification. There are however other stators out there along the same price as the electrex.

In regards to the starting problems, especially the hot starting ptoblems, a slight modification to the pick-up coils seems to solve this problem.

From the VN750 yahoo group files..
Possible solution to hard starting your VN7XX when hot.

Problem: Once my bike was good and hot, I would pretty regularly have problems restarting it after shutting it off for refueling, etc.... Once the starter was engaged, the bike would continuously turn over but never fire. After some e-mail discussion with Gary Versteegh from the main VROC board, I adjusted my pick up coils as described below. This seems to have eliminated my hard starting problems. This procedure may or may not solve your hard starting problems. Also, please note that the pick up coils are not designed from factory to be adjustable. This procedure requires modification to the stock components.

If you have any question, feel free to send me an e-mail to [email protected]. I will be happy to answer any questions.

Adjustment of pick up coils.
Remove the 3 phillips head screws on the left side. This will allow you to remove the pick up coil cover. You will need to place something under the bike to catch the oil although oil loss will be minimal. A rag was enough for me. Once the screws are removed, the cover should either come right off or you may need to pull on it. Mine was on pretty good and I had to physically pull on it to get it loose. The three screws and the cover all have separate o-rings. Once the cover is off, you will see the two pick up coils mounted to the stator cover inside two holes. They are mounted at roughly the 9:00 and 11:00 o'clock positions. Behind the stator cover, there is a rotor. You may need to rotate the rotor using a socket wrench on the shaft bolt in the center to align the small "plate" on the rotor with one of the pick up coils so that you can measure the clearance. Once you have measured one, rotate the rotor again so that you can measure the other. Gary recommends .020 clearance. Mine were about .030 or more. To adjust the clearance, remove the two screws which secure the pick up coils to the stator cover. You will most likely need to slightly elongate or slot the holes in the "ears" of the pick up coil mounting brackets. Gary indicates that a chain saw file works well for this but I used a rotary tool with a small grinding wheel on it. You will also see that there are 3 small protrusions coming out of the stator cover that each of the mounting
"ears" of the pick up coils fit into for proper placement from the factory. You will most likely have to knock the one closest to the center off to be able to make the necessary adjustment. A sharp chisel works well for this although you may want to cover the holes in the stator cover with something to prevent the little piece from falling inside the engine. Once the protrusions are knocked off and the holes are elongated, it is time to put the pick up coils back on. Set them back in their holes and start the screws. Place your .020" feeler gauge between the coil and the rotor "plate" and tighten the screws. Once you are satisfied with the clearance, tighten down the screws and do the same with the other coil. Gary recommends that you use both an impact screw driver and lock tite on the screws. I don't have an impact driver but I did use lock tite. Once both are set, put everything back together and test it out. I don't have a digital camera or I would have taken and posted some pics but you can look through the pictures in the Clymer's manual to get an idea of what I am talking about. In my manual (I assume they are all pretty much the same) the pictures on pages 296 to 302 should give you an idea of what I am talking about.

Note: This adjustment DOES NOT require removal or tilting of the engine. Just removal of the side cover held on by the three phillips head screws on the left side.
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Sorry, Lootux, I can't supply you with additional information. I didn't make any notes while I was making the modifications. I would suggest that you find someone with some electrical knowledge and use my info as a guide only.

Sorry I'm so late with this reply, but I was out of town.

There is no excuse for stator failure. A properly designed stator should never fail! There are no moving parts within the stator, so it is simply a matter of insulation failure over time.

I realize that there is circulating oil with some washing effects, however, the failures that I have seen are a breakdown of the insulation around the sharp corners of the stator windings. The manufacture should chamfer these sharp corners and provide a better insulation system for the windings.

On the frame cutting, I see a way to do it. There are several threaded bold holes that can be used to mount a plate, or plates on the front side after the tube is cut. I think I can use 1/4 in aluminum plates. The bottom end can be fitted with either an internal bar, or external pipe.

I can fit the plates before cutting the frame, however the bar piece may have to be fitted after the cut to the lower frame piece. In any event, I looks a lot easier than pulling the engine again. And since I wouldn't use welds, I can replace the stator weekly, if need be, after I have made the modification.

So far, my power inverter has worked with the single short in the stator. I'll see how long it goes before I need to put in a new stator entirely.

Thanks for your advice.
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