Kawasaki VN750 Forum banner
1 - 20 of 24 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter · #1 ·
hello, i have a 1989 vulcan 750.:motorcycl ,after i ride for about 20 or 30 miles or so ,i get off the gas and the poping start. how can i stop the poping?
 

·
Premium Member
Joined
·
382 Posts
You can richen up the fuel mixture and/or put marbles in the hoses for the emissions. Another possible cause is an exaust leak. Most VN750s pop a little on decel

Look through the vulcan versus
 

·
Registered
Joined
·
198 Posts
My bet would also be that it's running a little too lean. Try choking it just a little tiny bit and see if it improves the backfiring.
 

·
Registered
Joined
·
271 Posts
Do you have the stock exhaust on the bike?. If you do, you might have an exhaust leak on that cyclinder. Look at your carbs, and see if you can locate the little lead plug that covers the air/fuel mix screw. If the plugs are gone, then someone has been messin with the adjustment. If that is the case, turn the screw counter clockwise a 1/4 turn to richen up the mix. That should do it for ya unless you have an exhaust leak.
 

·
Premium Member
Joined
·
4,054 Posts
BIG_Anthony said:
hello, i have a 1989 vulcan 750.:motorcycl ,after i ride for about 20 or 30 miles or so ,i get off the gas and the poping start. how can i stop the poping?

On an 89, I'll bet your emissions system is non functional. I would marble the thing and that would probably take care of most of it. Of course, you probably have a solution to this by now.
 

·
Premium Member
Joined
·
176 Posts
I have a 2006 and it does that popping I think it sounds neat.I dont think it will hurt your bike if you leave it alone as long as its not an exhaust leak.But by all means if it drives you nuts follow the advice given.
 

·
and the Adventure Cycle
Joined
·
6,141 Posts
Eggnog said:
I have a 2006 and it does that popping I think it sounds neat.I dont think it will hurt your bike if you leave it alone as long as its not an exhaust leak.But by all means if it drives you nuts follow the advice given.
Ahh, good to hear that I'm not alone in wanting to keep the popping!!
I don't really mind it.
Keep On Poppin' !!​
 

·
Premium Member
Joined
·
4,054 Posts
Before I "marbled" my popping would be an occasional explosion loud enough to wake the dead, along with a continuous softer popping as I decelled. Now, it occasionally makes a soft popcorn popping sound as I decell and I think it sounds pretty snappy, and I'd have to say I like it a lot. The pre-marbled explosion and louder popping was a little imbarrasing to me, but that's just me. I really like the way my bike sounds now, with marbles, and end of stock pipes drilled. It rumbles and I don't hear any other bikes around here that sound like it, which is kind of cool.
 

·
and the Adventure Cycle
Joined
·
6,141 Posts
fergy said:
Before I "marbled" my popping would be an occasional explosion loud enough to wake the dead,
Mine does that if I don't let the starter run long enough to fire the bike up.
When I hit the starter a second time....
BAM!​
Almost like a gun shot ! I just see it as the starting gun firing to get the ride in motion !!
 

·
Once Banned
Joined
·
2,125 Posts
So Ferg, you still got stock pipes? Mine doesn't ever get a good backfire anymore, probably because I can tell when it's about to do it and either shift to a lower gear or just pull the clutch in. It does, however, burble while slowing down, which is cool. So how does your bike sound with just the drilled holes? Some say it sounds "tinny." Do you still have the belly?
 

·
Premium Member
Joined
·
4,054 Posts
cegodsey said:
Do you still have the belly?
:p You've seen my pictures!

Seriously, yes I still have the GB. My pipes are drilled all the way around, not just two or three holes. It did deepen the sound, made it a little louder, especially when you get on the throttle, but it's not tinny sounding at all. I've heard aftermarket pipes that sounded tinny and this ain't it. Problem is, once you drill em, you're gona have to live with it. But, I think it sounds just right.

I don't have the backfiring at all anymore, just a nice low rumble when backing off the throttle.

I remember before I marbled, one morning I did the stutter starter button thing, then when I hit it again, BOOM! Under my carport it sounded like someone fired a shotgun behind me. I looked my bike over expecting to see a huge hole in something! Talking about breaking out in an instant sweat! Wifey stuck her head out the back door and said what was that? I said, uh, just starting the bike sweetie... She frowned at me and muttered something about the neighbors and small animals and went back in..
 

·
Registered
Joined
·
17 Posts
I had the "Sonic Boom" about two weeks ago while starting in the morning. I did not realize it was because of the second start attempt, but yes that is what happend. To add to the noise it was at 6 AM in our townhouse parking lot which is like a canyon with a long row of townhouses on either side. I wonder how many of the neighbors I woke up. Luckily my wife had already left for work. ;-)
 

·
HAWK
Joined
·
2,576 Posts
Vaccam said:
I had the "Sonic Boom" about two weeks ago while starting in the morning. I did not realize it was because of the second start attempt, but yes that is what happend. To add to the noise it was at 6 AM in our townhouse parking lot which is like a canyon with a long row of townhouses on either side. I wonder how many of the neighbors I woke up. Luckily my wife had already left for work. ;-)
Do you still have a Wet Cell BAtt? That is the only time I have herd of a 750 doing that, mine did at work in the garage, Very loud backfire. The weaker wet Battery will do that, the MF wont, I havent herd of anyone having that problem after putting in a MF.
 

·
HAWK
Joined
·
2,576 Posts
There you go, it was a big bang wasent it:BLAM:
Kinda fun to scare people.
 

·
Premium Member
Joined
·
100 Posts
VN750s just pop on decel

I worked on my exhaust headers to clean them up real good so no air could get in to make any explosions in the pipes. Then I saw that, at least my bike, has some kind of air injection into the exhaust pipes to reduce emissions. If air is going into those pipes, then the unburnt gas is going to pop in that hot pipe when air hits it. (Unburnt gas comes, if I'm not mistaken, from the very high carburetor vacuum that develops on decel. That high vacuum sucks extra gas through the jets and it doesn't have enough air coming into the carb to burn it in the cylinder.)

I think it's just got to snap, crackle, and pop.

The marbles is sure an intriguing idea; never heard of that one.
 

·
Premium Member
Joined
·
4,054 Posts
The "marbling" or "coasterizing" are both methods of blocking off the anti smog stuff on the bike. This has been an issue on KAW and probably most other metric bikes for years. Apparently they put this on the bike to pass US requirements, but the devices don't last long because of the carbon buildup and heat and you start getting lots of backfiring over time. Both of my KZ's had the problem and I bypassed the entire system on both. Kept it in case it ever became an "inspection" issue. Read about this in the Vulcan Verses if you want to know more.

The unburnt fuel that gets ignited when fresh air is introduced isn't there because of the enormous amount of fuel drawn into the combustion chamber by our massive vacuum. The carb does a fine job of metering the fuel to air ratio. It is related to the gasoline and the additives in the gas that lack what is needed to better vaporize the mix and be completely burned. You have the same issue on cars and trucks even with fuel injection. There is too much surface tension in almost all gasoline and the mist or vapor contains globs or beads of gas that didn't vaporize and remain unburned. Some fuel additives reduce the surface tension of gasoline, make it vaporize better and make it burn more completely.

Having two spark plugs in a cylinder should help burn the fuel more effectively giving you more power and less waste. There is a company that makes special spark plug wires that have some electronics in the wire (looks similar to a load on an antenna mast) that charge up and when the plug wire is supposed to send a spark, this device sends a continuous charge to the plug so that it sparks continuously for maybe 3-4 times longer than a conventional system, burning more fuel, which in turn, requires less fuel to get more power... Haven't tested these but it sounds interesting...

http://www.kikerperformance.com/index.htm
 
1 - 20 of 24 Posts
Top