Missing and backfire - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 10 (permalink) Old 01-04-2011, 02:10 PM Thread Starter
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Missing and backfire

My 750 has to sit outside, just he nature of the beast. Its put away for winter now (North Dakota) but this summer it was rode about 1500-2000 miles over a couple months then not drove much the last months of summer. When I did drive it, when first started it had a intermitent miss, it seemed to go away with some riding. We had alot of rain this summer so put it down to rain and moisture. I used some heet in tank but it disnt seem to help. If road everyday it seemed fine, but if it sat a week or two it was the same, run crappy but after maybe 20 minutes it ran fine. Well the very end of summer it wasnt put away till it was really cold, so it handnt been run for maybe 4 weeks. I haave storage about 10 miles out of town, all slow 25-40 MPH traffic, it never came out of the random miss thing.. even when warmed up. SO the water in tank thing souldnt be the problem. I filled it up before parking (i know that a love/hate thing).

So where will i start looking when summer comes (yes, long ways away, but already thinking about it). It starts easy and idles fine, but that random miss that doesnt seem to go away now is a problem. Of ourse it was just the final ride of year it showed up, maybe it will be gone in spring. But the miss till warm was consitant at end of year when it didnt do it all in spring- summer.
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post #2 of 10 (permalink) Old 01-05-2011, 03:50 AM
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You should start at the carbs, sounds like water to me. You will need to find a pan to fit under the bike, and if I'm not mistaken, you can put a piece of tubing on the drain on the bottom of the bowls. Make sure they are long enough to get under the bike into the pan, and open the drian screws and drain them into the pan. BE SAFE! No sparks, do it in the open if you can, and while they are draining, open the petcock to PRI so the fuel will run into the carbs to help flush out the gunk.
That should cure the problem, if not then you most likely will have clogged jets in the carbs.
Check over the rest of the bike, ie the plugs, wires, and battery to see if you have good voltage to the coils.
If you have any other questions, post on here, and I'm sure someone with more expertise than myself can help you.
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post #3 of 10 (permalink) Old 01-05-2011, 09:31 AM
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I'd put some Sea Foam in it. Drain the carbs and refill with straight Sea Foam. Get rid of the gas in the tank and put 1/2 can in with fresh gas. When you take her out of storage, remember to drain the Sea Foam out of the carbs.

I'm keepin' all the left over parts. I'm gonna use 'em to build another bike!
"Black Beauty"
1989 VN750 acquired December, 2008, 6,711 miles
Currently 23,298 miles

Old Blue
2001 Honda CMX250 Rebel acquired July, 2008

1987 VN750 project bike, acquired August, 2009, 33,000 miles and balancer sticking out of the case, currently awaiting attention and parts
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post #4 of 10 (permalink) Old 01-13-2011, 11:32 AM Thread Starter
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thanks, 3 months out and Im already thinking about it.. I will update then..
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post #5 of 10 (permalink) Old 01-13-2011, 01:16 PM
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Hey Clok,
I think Raker and Flites' suggestions are sound. I think that the only thing I would add, is that you have ample time to really check the electrics on the bike. I think I would get that gel battery, change out the plugs to iridiums, check the plug wires and boots for cracks or environmental intrusion, inspect the coil connections, and the feeds from the pickups. Heck, if I had time and the means, I would do the pickup mod for .020 gap. Then, I would definitely check the charging system and ensure all electrical frame and engine ground points on the bike were clean and undamaged.
whistle while you work, cause it's all good easy stuff to check for a trouble free approaching riding season. Lot's of good info in the 'Verses' for all this stuff.

Good Luck, and I hope with these efforts, you never know what that problem in 2010 was!

~~C8> Ratt
'91 VN750 - Cosmic Splendor/Candy Wine
Done: Coastered, .020 ign., Iridiums, VM
Plexistar II, MCCT's, Relocated MOSFET
Next: LED's
Will Do: Horns, Shave(maybe)

Last edited by ZCraggRatt; 01-17-2011 at 08:41 AM.
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post #6 of 10 (permalink) Old 07-12-2011, 01:28 PM Thread Starter
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All excited in winter to ride, summer is here and I finally got out to my storage and started it up (new gel battery). Fired right up, but one cylinder is not fireing. i didnt have tools to mess with it much, going to drain carbs and fill with some seafoam and see. im thinking plugged needle valve .. Will update .... next week out of town for business this week.
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post #7 of 10 (permalink) Old 05-02-2012, 12:11 PM Thread Starter
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update a year later.. but i hate following a problem post and not seeing it completed.

Pulled bike out this spring, pulled carbs, fixed problems... sort of. One carb was stuck so it was constantly poring fuel in.. ran fine as long as you where rigning it hard.. but then would flood. Cleaning carbs solved problems, starts and euns nice now.

BUT... when warm it backfires on start.. and the thing smells gassy all the time. it runs perfect at speed, it idles great.. but when warm on a restart it will backfire and seems like its flooding a bit still. I do have a good battery (new one gel).. I think I will mess with idle adjust.. maybe am just running it to rich. its so nice to have it running great again.
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post #8 of 10 (permalink) Old 05-02-2012, 12:39 PM
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Nice to hear that you are up and running, and thanks for the (timely ) update.

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars

1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #9 of 10 (permalink) Old 05-02-2012, 09:03 PM
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Hey clok, check your float needle seals, even though you got everything moving freely now, the seals may be worn and still over feeding the fuel
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post #10 of 10 (permalink) Old 06-08-2012, 12:29 AM Thread Starter
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Just an update, bike runs excellent. I think there might be something to the needle valve seals... they whre , how should i put this? just ok.. im not losing fuel and its not flooding anymore just the smell of gas. I think i have a gas tank cap issue.. my strange random miss came back after the bike got left outside in the rain.. if the bike is inside all the time, no issues other then slight gas smell. sits outside.. after a week or so it will randome miss for about 15 minutes.. come out of it fine and run great... must be getting some water in tank.. bad seal of some type.. would explain gas smell.
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