SuzukiSavage.com - big bang when shutting off engine

dwheeler

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big bang when shutting off engine
08/17/08 at 20:06:50

Just purshased my first suzuki last tuesday. A 2007 S-40. Really like it but when riding home after about an hour on the road I stopped to get some gas. When I turned off the ignition I got a big bang from the exhaust. Was wondering if this will hurt the valves if I don't get it fixed.Sounded like a big backfire. The bike only has 700 miles on it.

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Bear

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Re: big bang when shutting off engine
Reply #1 - 08/17/08 at 22:03:09

I bought a 2008 a month ago. Same problem. Really LOUD bang, like a shotgun blast. Embarrassing as hell. Try this..when you want to kill the engine, just pull out the choke at the same time you hit the kill switch . No more bang. Remember to turn off the key.
I also get some "pops" out of the muffler when I open it up and then slam the throttle closed at speed. Solution...stop doing that.

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verslagen1

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Re: big bang when shutting off engine
Reply #2 - 08/17/08 at 22:32:01

Just a big bang on shut off? And not at every shift?

Most likely you need to adjust the idle mixture. And being a new bike there's probably a brass plug covering it. Search Idle mixture plug and you should find hundreds of ref's to it.

Also could be loose header bolts or muffler clamp. But those would give you a pop at every shift.

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ratdog472 Full Member Offline The Savages are restless... Posts: 156 Springfield, MO Gender:	Re: big bang when shutting off engine Reply #3 - 08/17/08 at 23:11:30 Or it could be a rev just before shut-off. Best thing is to let it idle 2-3 seconds before shut-off and that should cure it if it isn't a mechanical issue.
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Rockin_John

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Re: big bang when shutting off engine
Reply #4 - 08/17/08 at 23:40:14

Agreed with ratdog: first, try letting it idle for a few seconds before shutdown. If that doesn't reduce the bang to a small thump; then adjustment of the idle mix screw is in order. Most of us get it adjusted down to a part-time little burp at shutdown and just live with that. (I always thought it was kind of cool sounding!)

At that point I don't think any damage is being done, but consistent shotgun blasts at every shutdown are bound to damage something serious eventually... Undecided

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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 28637 Tucson Az Gender:	Re: big bang when shutting off engine Reply #5 - 08/18/08 at 00:45:57 Maybe we're not all actually reducing it, but are going deaf from it... "What pop?" Sounds like a mellow "whoomp.." to me now too...I hope I've just adjusted it out.
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blacksheep23

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Re: big bang when shutting off engine
Reply #6 - 08/18/08 at 05:28:43

Bear wrote on 08/17/08 at 22:03:09:

I bought a 2008 a month ago. Same problem. Really LOUD bang, like a shotgun blast. Embarrassing as hell. Try this..when you want to kill the engine, just pull out the choke at the same time you hit the kill switch . No more bang. Remember to turn off the key.
I also get some "pops" out of the muffler when I open it up and then slam the throttle closed at speed. Solution...stop doing that.

or u can slowly let go the clutch in 1st gear till it abt to stall and click the switch.

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skrapiron -FSO

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Re: big bang when shutting off engine
Reply #7 - 08/18/08 at 05:29:13

That's perfectly normal for a factory tuned S40.

The carb is tuned WAY lean to meet EPA emissions requirements and to deliver maximum fuel efficiency. The shut down pop (or howitzer blast as it may be) is normal and to my knowledge, will harm nothing. It is embarassing, especially when it happens near a police officer in the middle of a traffic stop.

If you don't want to monkey with the carb settings (still under warranty) there is something you can do to reduce or eliminate the 'honey, I'm home' bang all together. Just before you go to shut off the bike, put it in neutral, then reach down to the choke. Pull the choke knob out one click, then turn the key off. Using the choke will cause a momentarily super rich condition which will reduce or eliminate the shutdown bang. Just remember to push the choke all the way in once it is off.

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Charon

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Re: big bang when shutting off engine
Reply #8 - 08/18/08 at 05:50:47

My '07 has never done the "Shutdown Blast." It backfires sometimes when I shut off the throttle, but not always. I don't remember it ever backfiring during a shift. I have removed the cover over the pilot screw and adjusted that, but it didn't seem to make any noticeable change. I tried raising the needle (white spacer mod, Stage 1), which did not cure the backfire but had a dire effect on fuel mileage. Perhaps the fact that I live at 1800 feet altitude makes a difference.

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1st2know

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Re: big bang when shutting off engine
Reply #9 - 08/18/08 at 07:40:36

My Big Bang theory is that the vac line to the petcook is cracked or loose.

This happened to me. Shut the thing down, count to 3 and watch the birds scatter as the Savage relieves itself of surplus gas - It was fun, but I felt that the socially responsible thing to do was to fix it. Replaced the vac hose, tweeked the idle, no more bang.

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07S40rider

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Re: big bang when shutting off engine
Reply #10 - 08/18/08 at 17:36:20

I have chosen to make a game out of it. when I get ready to shut down, I know there is going to be a 'puff' or a 'whomp' or something similar. I try to time it so that I flip the side stand down at the exact time - or maybe do the finger/gun thing and act like I am shooting the ceiling of my garage. Cheesy

. What can I say, I am easily amused.

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"One mans McGoofy is another mans McCuff - its like pure magic in a yellow rubber gadget!"

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Sandy Koocanusa Serious Thumper Offline Don't blame me. I didn't vote for him. Posts: 1878 Bigfork, MT Gender:	Re: big bang when shutting off engine Reply #11 - 08/18/08 at 17:43:09 If you get the timing all worked out, go to the mall and try it. Park in a busy area, yell "PULL!" and fling the McGoofy up in the air like a clay pigeon. Then "shotgun" it out of the air as the bike sounds off. Just make sure to put the optional face mask on your tinfoil hat, in case someone is there who knows you.
Back to top	Savage: (adj)1. Wild 2. Uncivilized : Primitive 3. Ferocious 4. Cruel or merciless : Brutal --- Webster's. (n.) 1. A motorcycle named for its seat.--- Sandy's unabridged IP Logged

EssForty

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Re: big bang when shutting off engine
Reply #12 - 08/18/08 at 18:57:12

1st2know wrote on 08/18/08 at 07:40:36:

My Big Bang theory is that the vac line to the petcook is cracked or loose.

This happened to me. Shut the thing down, count to 3 and watch the birds scatter as the Savage relieves itself of surplus gas - It was fun, but I felt that the socially responsible thing to do was to fix it. Replaced the vac hose, tweeked the idle, no more bang.

I recently installed the ENM digital tach. During the process, I removed my tank to route the wires, which of course involved disconnecting the vac hose, etc. I put it all back together, and when I went for a ride the next day I pulled into the gas station and cut off the engine and had the same shotgun blast described. First time it ever did more than a mild puff at cutoff. Then when I got back home the same thing happened again at shutoff. BLAM! Had to pull my wife's cat down off the ceiling after that one!

Anyhow, I checked my vac line, adjusted the choke, dialed down the idle (the new digital tach makes it easy) and then drove a few more miles. Stopped & started it about 8 more times without more than a typical puff.

Next job is to patch the claw marks in the ceiling. Wink

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06 S40, Deuce shield, OEM saddlebags & Engine Guard, ENM tach, Sigma 1106 Speedo, oil pressure & voltage gauges, grip puppies, Kuryakyn Ellipse mirrors, ISO pegs & throttle boss

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07S40rider

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Re: big bang when shutting off engine
Reply #13 - 08/18/08 at 20:09:43

Sandy Koocanusa wrote on 08/18/08 at 17:43:09:

If you get the timing all worked out, go to the mall and try it. Park in a busy area, yell "PULL!" and fling the McGoofy up in the air like a clay pigeon. Then "shotgun" it out of the air as the bike sounds off. Just make sure to put the optional face mask on your tinfoil hat, in case someone is there who knows you.

NOW you are talking my kind of fun! although the middle TN gang bangers would probably start shooting back pretty quick and ruin all my fun. Tongue

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"One mans McGoofy is another mans McCuff - its like pure magic in a yellow rubber gadget!"

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dwheeler

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Re: big bang when shutting off engine
Reply #14 - 08/26/08 at 08:02:45

I tried pulling the choke out just before shutdown and this really works! No more big bang. However I was telling a friend of mine what I was doing and he aid that by choking it just before shutdown I would be causing gas to wash the oil away in the cylinder and would eventually hurt the engine. Any opions on this would be welcome. Would the excess gas from choking cause some of the oil in the cylinder to be washed away and lead to premature engine failure? He said that the excess gas would also wind up mixed in with the oil supply.

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