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Cruiser
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Discussion Starter · #1 · (Edited)
Hello,

This is my first post on VN750.com but I have been reading a lot recently on the forums. I recently bought a 1993 Vulcan 750 with around 18k miles. When I went the look at it the guy started it up with relatively no trouble. Took a couple seconds but it fire up. I took it for a ride and it ran fine so I bought it. A couple days later I tried to start it the first time at my house and had a lot of trouble. I ended up running the battery down and had to jump start it. It started right up when I hooked up the jumper cables.

So naturally I thought that maybe it was a bad battery. Luckily the battery was less than 90 days old and the guy I bought it from gave me the receipt. So this weekend I went and exchanged the battery. So I charged and installed it expecting to put it on and it fire right up. Wrong.....

The bike runs great once you get it started and I checked the battery with a voltage meter and the bike is charging when it is running. The problem is I can turn it off after I get it started and try to immediately try to start it back up and it won't. So I dont think it is the battery at this point. Every time I hook up jumper cables or my battery pack jump starter it fires right up. Is it possible that the ignition system is weak and only gets enough juice to start when the battery gets a boost? I did take all the spark plugs out and they didn't look like the bike is running lean or rich. They looked as they should and each of them was getting a spark. I guess I'm just wondering how strong that spark is.

Any help with this issue would be greatly appreciated!

I'm very frustrated with it at this point as I am supposed to take a big motorcycle trip with my cousin in September. I now have less than a month and an unreliable bike. I'm starting to think that I should have kept my 1982 Yamaha Virago....

Thanks,
Jeremy
 

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If only it had 6th gear..
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1,100 Posts
Hang in there Jeremy, these are decent bikes, yours is just needing some tlc. If it runs good when you get it going and rides well, I don't think you've got anything major to deal with. Does it act differently when cold? Considering that it starts when you put a boost on it leads me to the coils and/or pick ups. You're getting a spark obviously but it may not be a hot enough spark when you're cranking the starter. 1st buy a set of iridium plugs. People on here swear by them. Haven't got them myself yet but plan to next season. 2nd, There are some threads on here that talk about coil modifications, running the power to the coils right off the battery instead of the harness, and the pick up mod, changing the distance on the ignition pick ups to a closer tolerance. Both of these mods mention easier cold and hot starting and overall improvement in performance. Take a look in the electrical forums for those and others will jump in and help, there are a lot of good people on

Oh, it might be good to try and look at the spark your coil is putting out. Maybe in a garage or at night? It should be blue, not orange.
 

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Linkmeister Supreme
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7,960 Posts
Welcome to the Vulcan madness Chosen777.

If your present battery isn`t a Maintenance Free-AGM style similar to this DEKA, get one the next time you need a new battery:
http://cgi.ebay.com/ebaymotors/Deka...em&pt=Other_Vehicle_Parts&hash=item3eee173adb

You are going to want NGK Iridium DPR7EIX-9 plugs sooner than later, so try them first.
Many members have cured the hot and cold starting problems with just a new MF-AGM battery and the Iridium plugs.
If the bike still has starting issues try the following.

Ignition coil direct to battery mod:
http://www.vn750.com/forum/showthread.php?t=17276

Pickup coil adjustment with pictures:
http://www.vn750.com/forum/showthread.php?t=18550&highlight=pick+up+coil+mod
This mod may work by slightly advancing the ignition timing.
 

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Cruiser
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Discussion Starter · #4 ·
Oh, it might be good to try and look at the spark your coil is putting out. Maybe in a garage or at night? It should be blue, not orange.
I did notice that the sparks weren't completely blue. They were orange with just a little bit of blue. Does this mean that they are not getting enough juice?

Thanks guys for the suggestions. I will have to check into the iridium plugs. I guess I need to get the voltage meter out and see if I'm losing power between the battery and the coils. If so could it just be a bad connection somewhere.

One thing I forgot to mention is I did see one of my plug wires sparking to the frame at one point. Could one plug wire shorting out prevent it from starting?

Sorry when it comes to electrical/ignition issues I'm a newbie....
 

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OlHoss nailed it again...follow his advice and it should set you up fine... also if you are getting a spark on the frame from the plug wires that is bad!.. replace the wires asap!
 

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Cruiser
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Discussion Starter · #6 ·
Wow! I just check the price on the Iridium Plugs and they were about $9 a piece....Does that sound about right?
 

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Cruiser
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Discussion Starter · #8 ·
Since I have a brand new battery I will probably wait on getting the sealed gel cell battery. I have had nothing but trouble with the wet cell batteries since I started riding. They usually only last a year or year and a half.
 

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Cruiser
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Discussion Starter · #9 ·
So if I am getting a weak spark how would I go about checking the voltage of the power getting to the spark plugs? Just pull the plug wire and stick the positive side of my meter in the plug wire and ground to the frame? Then hit the start button?
 

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I payed about $8 for my Iridiums.

You already have some good advice, you should definitely get a new set of spark plug wires if they're "leaking".

On an unrelated note, when you get the bike up and running don't forget to do a spline lube before taking a big trip on it!
 

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Cruiser
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Discussion Starter · #11 · (Edited)
I ran into another unrelated issue yesterday as well. The guy I bought it from said that he broke the choke cable while adjusting the handlebars. So I got a new cable and installed it yesterday. But where the handlebars were when I turned them right all the way it was applying the choke. I had to adjust the handle bars almost straight up in order for it not to choke while turning all the way right. Is this the normal position of the handlebars or did I get a choke cable that is slightly too short? It was a lot more comfortable to ride with the handlebars a little lower and slanted back some.
 

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Super Moderator
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If it starts with a jump... I suspect the battery you have is weak. You should get it load tested at an auto parts store. Just because you get 12 volts does not mean the battery is good...even if it is new.

Choke position us related to starting the bike, I'd get that sorted out too.
 

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Super Moderator
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I guess I should ask exactly how you are " jump starting" the bike? Is this with a car battery? (car not running I hope)

I have seen folks get two or three bad batteries in a row, so how new they are means nothing. Are you sure theses batteries have the correct CCA for this bike?

You should be able to adjust the handlebars without effecting the choke... So not sure what's wrong there.

Try checking all the connections from your battery and coils... Your spark plug wires should of course not arc to the frame....
 

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Cruiser
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Discussion Starter · #16 ·
I jumped it with a car battery once (not running) and another time with a portable jump starter.

Wow, that is crazy. I guess I never thought that 2 batteries in a row would be bad but I guess it is very possible.

I guess my thinking was that if the battery was weak then I wouldn't be able to attempt to start it for long periods of time. (of course not holding the start button for long periods of time)

I'm thinking that the choke cable I got is slightly too short. I have it adjusted to be as long as possible. And it works where it is but it almost looks like I have ape hangers with the handlebars so far up...haha

I will look through all the wiring tonight and make sure all the connections are good.

I have found used coils with plug wires on ebay for under $50. Do you suggest I go ahead and order them?
 

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If only it had 6th gear..
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Ok, so you have good advice from everybody as well as the links to the mods I mentioned earlier (thanks OlHoss). I think you'll be wasting money on coils. The plug wire arcing to the frame is a good indication that your wires are losing a large bit of voltage to your plugs. You only saw one arc, but I bet there are many others along the wires that you don't see. That surely is taking away from your spark power. I usually replace a set of wires if one is found questionable because the others are probably gonna jump ship soon anyway. These bikes seem to be sensitive to ignition problems so start with iridiums and decent wires.

The choke cable-check how it runs to the bracket between the carbs. I noticed when I put my carbs back in the cable didn't have a lot of slack to play with and the first time I had it positioned wrong. I have my handlebars leaning back generously and there's no problem with cable length. You might check the part number with the online manual at www.cheapcycleparts.com if you relied on someone at shop to pick your cable for you...

Question: what do you mean when you say you've got it adjusted to be as long as possible? The slack adjusters are for lever action and tension, not for length. The length is what it is. If you have the adjusters too tight then when you turn the bars, you will activate the choke lever because there isn't enough slack.
 

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Cruiser
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Discussion Starter · #18 ·
Just a quick update. I was able to adjust the handlebars by routing the choke cable a different/shorter way to the carb. But on a bad note I am now unable to even start the bike with the jumper cables or the portable jump starter. I emailed a local bike shop to get a price on new plug wires and iridium plugs. So hopefully that will fix it. I have noticed a clicking sound in the same area as the battery at times when I hit the start button. I think that it is coming from the round part that the positive battery cable connects directly to. Could that part be bad and need replacing?
 

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Cruiser
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Discussion Starter · #19 ·
I probably should mention that I got it started after some work and I just let it run. It ran for about 5 minutes fine and then just quit all of a sudden and that is when it wouldn't start back up even with the jumper cables.
 

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You can get cable by the foot and buy NGK caps and make your own cables... I don't have a link to the website that sells them though, but someone else here should know where to order them from.

You can also see if a local parts dealer has spark plug wires by the foot too. If they do, they probably have caps too. The part number for the NGK caps might be in the Vulcan Verses. Give it a good glance!

When I had a bad battery, I had trouble starting the bike even by jumping it with a car battery. When I took out the malfunctioning battery and used the jumper cables directly on the bike's positive and negative terminals, it started right up. Don't know why, but the bad battery was getting in the way somehow. If you do try this, just make sure not to let the positive touch anything on the frame. You can wrap something around it to prevent this, I used an old T-shirt I think. If you can use something made of rubber, even better.
 
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