Runs and Dies - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 15 (permalink) Old 09-25-2017, 10:34 PM Thread Starter
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Runs and Dies

So the short version is that my bike is starting and will run for a few minutes but then will die and not restart until I let it sit for a while. Only have done this twice so far and it has set for a couple hours in between because I had things to do, not sure that it needs to sit that long.

Longer story is that I was doing the pickup coil mod and broke the coil mounting tab so had the bike down for a while. I just rewired the bike (McInturff method) and replaced the stator cover (for the pickup tab). While doing this, the engine did come off the jack and was on the floor unexpectedly. No damage to the case or anything, but the front coil wires were still attached and they did get stretched. I put everything back together and had one pickup coil break free of the wiring. Replaced the coil with new OEM (ordered the whole shebang and cut the needed coil off, spliced it in with butt connector and heat shrink).

I took McInturff's ideas all the way and fully removed all of the excess wiring, including the RLU and the harness between the pickup coils and the ignitor box. I also replaced the R/R with a Shindengen SH775.

After all of that I got the bike back together and this is going on. I thought that the issue was flooding out, but then I tested for spark just for kicks. It seems that there is spark, but both cylinders seem to lose spark after it warms up (engine runs for a few minutes). After letting it sit for a while the spark is good again. First thing I did was look at the plugs. I had thought that I used Irridium plugs from the beginning but it turns out that I used OE plugs. So I replaced the plugs with Iridium plugs. Same condition. I ohmed out the pickup coils to see if there was something I might have missed or caused there, but they are good.

Anybody run into this before? Any thoughts?

- "Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."

'92 VN750
AGM battery, Iridium Spark plugs, Repaired/upgraded wiring per Mcinturff method, RLU removed, Repaired shift linkage, Exhaust baffles removed, Black ISO grips installed, installed SH775 R/R, Ignition coil relay mod, replaced stator housing.

Future projects: whatever it takes to keep riding

Currently working on: Light bar, LED upgrades, Dash cleanup/paint
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post #2 of 15 (permalink) Old 09-26-2017, 08:57 AM
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So you have a temperature related issue, they can be a pain. Based on your description i would make sure that the pick up coils are still connected when warm, maybe a coil or wire is broken but the ends are held together by the insulation and then seperate when they expand. I had an intermittent like that in a car ignition.

'99 Vulcan "Victoria"
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post #3 of 15 (permalink) Old 09-26-2017, 12:45 PM
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Ignition coils can fail with heat.

I would check the ohms on the coils when it's hot and not firing. If that's good, then I would check for voltage to the coils under the same conditions.

Also possible the CDi box is failing under heat.

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post #4 of 15 (permalink) Old 09-27-2017, 07:07 AM Thread Starter
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Well, as I read over this, I realize I should have mentioned that prior to this the only issue I had was the POOGS issue. Other than that the bike ran fantastic with zero issues but had been sitting for a couple years and only has about 13,000 miles on it (it's a 1992). That being said, I have found that my battery is very weak and needs to be replaced. I'm hoping this resolves the issue completely, but I have to do this regardless in order to continue testing. I will update when this is done one way or another but it's gonna be a couple days before I get a chance to do this. Thanks for the feedback and if anyone has any ideas in the meantime, please chime in. Will update asap.

- "Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."

'92 VN750
AGM battery, Iridium Spark plugs, Repaired/upgraded wiring per Mcinturff method, RLU removed, Repaired shift linkage, Exhaust baffles removed, Black ISO grips installed, installed SH775 R/R, Ignition coil relay mod, replaced stator housing.

Future projects: whatever it takes to keep riding

Currently working on: Light bar, LED upgrades, Dash cleanup/paint
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post #5 of 15 (permalink) Old 10-03-2017, 10:42 PM Thread Starter
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So, I replaced my battery and started testing. I've found that the rear cylinder suddenly has no spark. But, before testing further, my starter locked up. The starter has always been somewhat slow, so I'm not really surprised. Rebuild kit is on the way and I guess I'm going to be doing yet another oil change....

I'm thinking that after the starter is cranking again I'm going to test the wires from the ignitor box to the coils and possibly do the ignition coil relay mod.

This is so frustrating, but I absolutely love this bike and in the long run it will be worth it.

- "Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."

'92 VN750
AGM battery, Iridium Spark plugs, Repaired/upgraded wiring per Mcinturff method, RLU removed, Repaired shift linkage, Exhaust baffles removed, Black ISO grips installed, installed SH775 R/R, Ignition coil relay mod, replaced stator housing.

Future projects: whatever it takes to keep riding

Currently working on: Light bar, LED upgrades, Dash cleanup/paint
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post #6 of 15 (permalink) Old 10-04-2017, 01:54 AM
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"Blanche" loved the ignition coil mod,she had a problem with hot starts. Gave her the coil mod and she starts and runs like a new bike.

1985 700 Vulcan / Purchased 13,636 miles currently 19,126/Fork Seals & Dust Covers/Ignition Switch/AGM Battery/Hell Fire Windshield/River Roads Saddle Bags/Coil Relay Mod/2Wire Mod/RLU Bypass/Head Light Switch/Voltage monitor Green light/Mosfit R&R/Tuxedo Mod/Stator/Point Gap .020/ Dampers/Rear Signal & Brake Light LED'S/Rebuilt Shutoff Valve/Final Drive Gear Oil/Brake Shoes/Spline & Hub Lube/11 inch Progressive Shocks/De Goated/Engine Guard/Rejetted For K/N Pods/TOC mcct's
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post #7 of 15 (permalink) Old 10-11-2017, 02:26 AM Thread Starter
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so, I got my starter rebuilt and I reinstalled it. Did the coil relay mod as I was waiting on the starter, but I did mine a little differently by using a five pin relay and connecting each coil to its own pin of the relay (both pins 87 on the relay) and seems to work great. Spark is incredibly improved on the front cylinder, unfortunately it didn't resolve my rear cylinder no spark issue like I had hoped it would. Looking at it now, it should have been obvious that it wouldn't but this mod is completely worth doing anyways so no big deal.

Problem is that it isn't geting the signal voltage to the other connector on the coil. It's unrelated to this mod, but I've gotta track down the issue either between the pickup and igniter box, or between the igniter box and the ignition coil. Or it IS the igniter box. Here we go again.....

- "Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."

'92 VN750
AGM battery, Iridium Spark plugs, Repaired/upgraded wiring per Mcinturff method, RLU removed, Repaired shift linkage, Exhaust baffles removed, Black ISO grips installed, installed SH775 R/R, Ignition coil relay mod, replaced stator housing.

Future projects: whatever it takes to keep riding

Currently working on: Light bar, LED upgrades, Dash cleanup/paint
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post #8 of 15 (permalink) Old 10-16-2017, 12:30 AM Thread Starter
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Ok, so I'm getting very frustrated and need some help. The more I dig here on the forums, the more contradictory information I find.

Here's what I'm dealing with. I have figured out how I was approaching the idle issue wrong and think that I can handle that when I get the bike running again. But now I have lost spark on the rear coil. From what I have figured out, the pickup coils create a low amperage electromagnetic signal to the igniter box, which causes the igniter box to send ground to the coils causing them to send power to the spark plugs which jumps the gap and creates the spark which ignites the air fuel mixture in the cylinder. I have tested the coils a couple of ways. First I checked for continuity between both connectors at the igniter box for each pickup. I show continuity on both pickups from one connector to the other. That is to say, between black and black/yellow there is continuity and also between the black/red and black/white there is continuity. I also tested for ground on both pickups and found that there is ground on the black/white wire but not on the black wire. I am unable to measure the signal on the black/yellow and the black/red as I don't have a gauge that will read the approximately 0.5 amp signal. However I am willing to bet that the black/red will read correctly and the black/yellow will not read as the ground is not there on the black wire
Please someone help me with what this means. Bad pickup? Bad wire? Where do the pickup coils get the ground from? I am getting so tired of pulling things back apart that I just put back together and really need some direction. Please, anyone who can help. Thanks in advance.

- "Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."

'92 VN750
AGM battery, Iridium Spark plugs, Repaired/upgraded wiring per Mcinturff method, RLU removed, Repaired shift linkage, Exhaust baffles removed, Black ISO grips installed, installed SH775 R/R, Ignition coil relay mod, replaced stator housing.

Future projects: whatever it takes to keep riding

Currently working on: Light bar, LED upgrades, Dash cleanup/paint

Last edited by TR_Irish; 10-16-2017 at 12:36 AM. Reason: clarity
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post #9 of 15 (permalink) Old 10-16-2017, 03:41 AM
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Just looking in my repair manual, here's what I've dug up:

There's no mention of testing for ground except that none of the pickup coil leads (when disconnected from the ignitor box) should have continuity with ground. I wasn't sure if you meant you were getting ground on the ignitor box side of the connector or the pickup side.

The ignitor box should show 4-6 kOhm between any two of the following pins: 7,8,9,10 (where pickup coil leads attach). If you're not getting that, you've probably got a bad box.

That's all the solid info I have.
It does seem like each pickup coil should have a path to ground, (like you have on pin 10?), but I can't guarantee which wire on the other pickup (B/R or B/W) would be that ground. It's even possible that the ignitor box doesn't always provide a path to ground. Maybe someone else knows more.

1992 US-nonCA * tuxedo mod * r/r relocated

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Service Manual Download
Wiring Diagram + annotations * still undergoing revisions, but still more useful than the generic one. Let me know if you find mistakes or think something additional should be added
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post #10 of 15 (permalink) Old 10-16-2017, 04:16 AM Thread Starter
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Quote:
Originally Posted by Thorn View Post
I wasn't sure if you meant you were getting ground on the ignitor box side of the connector or the pickup side.
I mean that when probing the leads at the connector from the pickups, Not the box side, the pickup side has ground on the black wire. Not sure if it's supposed to or not. I'm assuming that it does and that the coil with the black wire is for the front cylinder (where I HAVE spark).
.
Two questions to clarify.
.
1) Each pickup coil having two leads coming from it, is one supposed to be ground?
2) which pickup coil is for which cylinder?
.
And I guess if the answer to #1 is yes, question 3 would be: Where does the pickup coil get ground from other than the junction box? As in, not connected to the box at all, should it have ground on one lead? If it doesn't then my problem is with the pickup that has ground when it isn't supposed to. If it does then my problem is with the one that isn't getting ground and should have it.

- "Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."

'92 VN750
AGM battery, Iridium Spark plugs, Repaired/upgraded wiring per Mcinturff method, RLU removed, Repaired shift linkage, Exhaust baffles removed, Black ISO grips installed, installed SH775 R/R, Ignition coil relay mod, replaced stator housing.

Future projects: whatever it takes to keep riding

Currently working on: Light bar, LED upgrades, Dash cleanup/paint
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