Ignition Issue - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 03-12-2012, 09:37 PM Thread Starter
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Ignition Issue

I have a 1985 vulcan vn700 a1 that is having an ignition issue. Sounds like timing but im not sure. I have rebuilt the carbs...nothing. i have replaced a faulty ignition coil...still nothing. wont rev past 2000 rpm without backfiring and misfiring. any help? what should i check into next?
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post #2 of 9 (permalink) Old 03-12-2012, 10:28 PM
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Welcome. So how does it start? does it idle ok? does it misfire at idle, or just 2000 rpm? The ignition timing should be at 5 degrees BTDC at 1,100 rpm, and advance to 25 degrees BTDC at 3500 rpm. The procedure for checking timing can be found in the Kawasaki manual which can be downloaded from this forum. It starts on page 15-20. The ignition timing is controlled by the IC igniter, and is not adjustable. If it is not right, you will need to replace the igniter.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
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post #3 of 9 (permalink) Old 03-13-2012, 12:54 AM
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Quote:
Originally Posted by chip88 View Post
I have a 1985 vulcan vn700 a1 that is having an ignition issue. Sounds like timing but im not sure. I have rebuilt the carbs...nothing. i have replaced a faulty ignition coil...still nothing. wont rev past 2000 rpm without backfiring and misfiring. any help? what should i check into next?
Hi Chip. Electrical issues suck.

Tell us a little more about what you have checked in the ignition system.

Have you checked the overall condition of wires and ignition components?
No cracked or worn insulation on wires?
Are the Batt(-) frame and engine ground wires clean and tight?
Have you looked at the pickup coils? Checked their resistance values?
Have you verified the wiring with the schematic?
verified all plug wires routed to the proper jug.
Have you checked for a nice fat blue spark from each spark plug?
Do you have a well charged strong battery?
Have you checked the spark timing with a timing light?

Check Kanucks thread for a downloadable service manual:
https://www.vn750.com/forum/showthread.php?t=17667

~~C8> Ratt
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Done: Coastered, .020 ign., Iridiums, VM
Plexistar II, MCCT's, Relocated MOSFET
Next: LED's
Will Do: Horns, Shave(maybe)

Last edited by ZCraggRatt; 03-13-2012 at 12:58 AM. Reason: Manual Link
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post #4 of 9 (permalink) Old 03-13-2012, 09:21 AM
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Won't rev past 2000 still sounds like a fuel issue to me you say you have rebuilt the carbs is everything back as it should be have you seated the inlet rubber boots correctly and got a good air tight seal
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post #5 of 9 (permalink) Old 03-13-2012, 09:46 AM
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How did the problem present itself... before or after the carb work? What was the situation when it started happening.
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post #6 of 9 (permalink) Old 03-13-2012, 03:16 PM Thread Starter
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Thanks everyone for responding. The problem started when i was riding home from work one day. It was running fine until all of the sudden one cylinder just went out sending me off to the side of the rode. After some research the first thing i tried to fix it was new spark plugs and wires. That didnt help very much so i moved on to the rebuild of the carbs. That helped the idle but that was it. It will start and idle fine but when you rev it to about 2000 rpms it backfires and misfires. So then after more research i decided that it might be the ignition coil for the rear cylinder. The issue was with the rear cylinder. So, because the rear and front ignition coils were the same i switched them to see if the problem would switch to the front cylinder because of the faulty coil. it did! so i was set on it being the coil. So i bought a new coil and put it on. didnt help the situation. so im still in the dark on what it is. if it is the igniter i cant afford the cost to buy a new one at almost $450!! all the wires seemed good. all of the sparks seemed good. my mechanic did check the timing and he said it was good but i will double check that. the battery is brand new and fully charged. the only thing i havent done is check the pickup coils resistence. any suggestions on how to do that? thanks again everybody
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post #7 of 9 (permalink) Old 03-13-2012, 07:17 PM
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the only thing i havent done is check the pickup coils resistence. any suggestions on how to do that?
From the Clymer manual,

Pickup Coil Testing
1. Remove the frame left hand side cover

2. Disconnect pickup coils 4-pin electrical connection containing 4 wires (1 b/y, 1 b, 1 b/w, and 1 b/r).

3. Set ohmmeter to R x 1000 and zero the test leads.
(My note here. These directions are for an analog meter. Digital meters don`t require zeroing.)

4. Check the resistance between the following wires in the pickup coil side of the 4-pin electrical connector.
a. Front cylinder: between the b/y and b terminals.
b. Rear cylinder: between b/w and b/r terminals.
Specified resistance is 355- 535 ohms.

5. If resistance is less than specified there is a short; if more the coil has an open.
In either case it must be replaced.

6. Set ohmmeter to highest setting and zero the leads.

7. Check resistance between each of the 4 wires in the pickup coil side of the 4-pin connector and chassis ground. Any meter reading less than infinity indicates a short and the pickup coil assembly must be replaced.

8. If coils check out OK, reconnect the electrical connector. Make sure it is free of corrosion and is tight.

(I suggest spraying with some electrical contact cleaner, dry completely and packing the male side of the connector with dielectric grease before snapping back together.)

9. Replace side cover.

(Someone here had a broken lead to the pickup coil and repaired it by soldering. Look out for that too.)

Hope this helps.

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
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July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15


TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/11-vn750-general-discussion/9127-top-ten-items-you-would-suggest-new-owner-do-his-new-ride.html
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post #8 of 9 (permalink) Old 03-14-2012, 07:43 PM
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Ya know, interesting thing about my '85....if I keep an engine oil level (measured on centerstand) full, I get starting probs, backfiring, etc. When I keep it "half", it runs like a top. I found that for whatever reason, when the lil window is full, oil coats my lower pickup coil and I lose that cyl. Dunno if its just a VN700 thing or common with others. Mebbe its just mine since we run castor earl in moters round heah...**



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post #9 of 9 (permalink) Old 03-15-2012, 04:01 PM
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No problem with mine Wolfie oil right up sight glass and runs fine
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