VN750 popping on deceleration - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 16 (permalink) Old 11-11-2011, 11:59 AM Thread Starter
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VN750 popping on deceleration

I have a 2001 Kawasaki Vulcan 750 that has a popping sound when decelerating. It didn't do this until after I had my accident. Now it does it every time I ride. It isn't really an issue from what I can tell, as most people have said it won't hurt anything. However, it's pretty annoying and bothersome for me and I'm sure cars around me don't like it. I planned to take it in to have it looked over anyway during the winter to make sure nothing is messed up on it from the accident, but I figured I would ask some people on here for their ideas or suggestions. I am pretty new to riding and I really don't know much about repairing bikes AT ALL. I'm a true newbie!
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post #2 of 16 (permalink) Old 11-11-2011, 12:24 PM
Crap, I WAS in 5th gear.
 
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Exhaust popping is caused by a lean condition in the exhaust. Search for "marble" in this forum, and check all your carb boots and vacuum lines- something might have been knocked loose is your accident.
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post #3 of 16 (permalink) Old 11-11-2011, 12:30 PM
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Accident? What hit the ground?

Check your header pipes where they bolt up to the cylinders and the clamps at the other end.

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post #4 of 16 (permalink) Old 11-11-2011, 09:28 PM
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If it weren't for the "accident" I would say it is caused by the air injection system if it still has one. Those things inject air into the exhaust, causing unburned fuel in the exhaust to ignite, making weird noises, and causing the exhaust to overheat. Need more details on the accident. I have read a number of posts on different forums about bikes not running right after just falling over. That is possible, but should be very temporary. Gas runs out of the carbs, oil can run out the crankcase vent and into the airbox, etc. If yours has been doing this for some time after the accident, then it is very likely that some part of the intake or exhaust system has been damaged.

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
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #5 of 16 (permalink) Old 11-14-2011, 12:09 PM Thread Starter
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Quote:
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Accident? What hit the ground?
Quote:
Originally Posted by VN750Rider/Jerry View Post
If it weren't for the "accident" I would say it is caused by the air injection system if it still has one. Those things inject air into the exhaust, causing unburned fuel in the exhaust to ignite, making weird noises, and causing the exhaust to overheat. Need more details on the accident. I have read a number of posts on different forums about bikes not running right after just falling over. That is possible, but should be very temporary. Gas runs out of the carbs, oil can run out the crankcase vent and into the airbox, etc. If yours has been doing this for some time after the accident, then it is very likely that some part of the intake or exhaust system has been damaged.
I was going about 35mph on the interstate and a car cut the person in front of me off and I made the mistake of only grabbing the front brake and way too hard, so i lost control of the bike (I had only been riding for about a month at the time) and the bike and myself only slid about 10-15 ft. I didn't hit any other vehicles. It has been doing the popping since then on deceleration. The only other issue I have had since the accident is that when the bike is first started, it has a clanking sound coming from the engine and then after the bike warms up, it's gone. The handlebars got a little bent, but thankfully the forks themselves didn't get bent so the bike is still very much ride-able. I actually rode 70 miles this past Saturday with no issues, just the popping and clanking until it warms up, then everything was fine. It was a rookie mistake and I have been very careful since then.
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post #6 of 16 (permalink) Old 11-14-2011, 12:55 PM
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Didn't really answer my question. (what hit the ground).


If you have been riding the bike for some time with no "popping" and it began after it fell over, I still would suspect the exhaust on whatever side touched down.

That said. From what I know...ALL stock Vulcans pop on decceleration. Why yours didn't before is more of a mystery to me than why it does now.

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post #7 of 16 (permalink) Old 11-14-2011, 01:06 PM Thread Starter
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Quote:
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Didn't really answer my question. (what hit the ground).


If you have been riding the bike for some time with no "popping" and it began after it fell over, I still would suspect the exhaust on whatever side touched down.

That said. From what I know...ALL stock Vulcans pop on decceleration. Why yours didn't before is more of a mystery to me than why it does now.
sorry. When it fell, the only stuff that really hit the ground was on the left side...so the shifter got scraped up a bit, as did some of the plastic and turn signals, and i guess the left side pipes would have had to have hit the ground as well.
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post #8 of 16 (permalink) Old 11-14-2011, 04:46 PM
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Hopefully the shifter shaft is still ok. When dropped on the left side, many times something breaks off the internal shift shaft, allowing it to have way to much in and out play, like over an inch.

Check the left side exhaust for any leaks, from the head to the tip of the muffler.

You didn't mention the "clanking" sound before, I doubt it has anything to do with the "popping". When the bike went down, did it continue to run for a few seconds? When you picked it up and restarted it, did the oil pressure light stay on very long? Many bikes have a serious design problem with the lubrication system, so when the bike is dropped, even if it is picked up and allowed to sit for a few minutes in the upright position, it will still run for as much as 30 seconds without oil pressure. I have never dropped a bike, but I've read about this on many different forums. For some reason, when the bike is on it's side, the oil pump loses it's prime, and it takes some time for it to start pumping again. It does not do this even after changing the oil, only if dropped or layed down in the horizontal position. I wonder if it ran long enough without oil to damage the engine.

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
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #9 of 16 (permalink) Old 11-14-2011, 05:24 PM Thread Starter
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as soon as I dropped the bike, it shut off...because I had the bike in 1st gear and didn't obviously pull in the clutch or anything, so it shut off automatically, which is why it didn't slide that far. The bike didn't start back up right away once I got it upright again, it took a couple minutes to start, but finally got it going and the oil pressure light didn't stay on any longer than normal.
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post #10 of 16 (permalink) Old 11-15-2011, 07:31 PM
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Quote:
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as soon as I dropped the bike, it shut off...because I had the bike in 1st gear and didn't obviously pull in the clutch or anything, so it shut off automatically, which is why it didn't slide that far. The bike didn't start back up right away once I got it upright again, it took a couple minutes to start, but finally got it going and the oil pressure light didn't stay on any longer than normal.
Great. Maybe the VN750 is one of those bikes that doesn't happen too. Then that probably rules out any internal engine damage. No part of the engine would contact the ground when you dropped it. It doesn't stick out far enough. But the left side exhaust is bolted solidly to the rear cylinder, and an impact to the exhaust could be transferred to the engine. Again check for any exhaust leaks. The popping, if it is more noticeable than before, is caused by something that changed. Was there any damage to the choke lever or cable?


The "clanking" sound that goes away after the engine warms up sounds suspiciously like the ACCTs have failed. That could have been caused by the force of an impact, even without touching the tensioners, if they were almost worn out anyway. Go to the "Vulcan Verses" and look up the "Grambo Trick" and try that. If that stops the noise, that pinpoints the problem. But even if it works, it will most likely be temporary. If that is it, then manual tensioners will fix the problem.

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
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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