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Message started by dwheeler on 08/17/08 at 20:06:50

Title: big bang when shutting off engine
Post by dwheeler on 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.

Title: Re: big bang when shutting off engine
Post by Bear 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.

Title: Re: big bang when shutting off engine
Post by verslagen1 on 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.

Title: Re: big bang when shutting off engine
Post by ratdog472 on 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.

Title: Re: big bang when shutting off engine
Post by Rockin_John on 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... :-/

Title: Re: big bang when shutting off engine
Post by serowbot on 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.

Title: Re: big bang when shutting off engine
Post by blacksheep23 on 08/18/08 at 05:28:43

23332E35292433410 wrote:

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

Title: Re: big bang when shutting off engine
Post by skrapiron on 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.

Title: Re: big bang when shutting off engine
Post by Charon on 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.

Title: Re: big bang when shutting off engine
Post by 1st2know 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.

Title: Re: big bang when shutting off engine
Post by 07S40rider on 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. :D. What can I say, I am easily amused.

Title: Re: big bang when shutting off engine
Post by Sandy Koocanusa 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.

Title: Re: big bang when shutting off engine
Post by EssForty on 08/18/08 at 18:57:12

115354124B4E4F57200 wrote:

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. ;)

Title: Re: big bang when shutting off engine
Post by 07S40rider on 08/18/08 at 20:09:43

0A0C0D0F12140F0E600 wrote:

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. :P

Title: Re: big bang when shutting off engine
Post by dwheeler on 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.

Title: Re: big bang when shutting off engine
Post by doc5446 on 08/26/08 at 08:56:41

2C2B4F282C6E7578796E1C0 wrote:

Sometimes I do the same thing myself. You guys remember the movie "Uncle Buck" with John Candy? Uncle Buck drives his teenage niece to high school and when he drops her off, he shuts off his enormous boat of a car and.....BAMMM!!!!! ;D

Title: Re: big bang when shutting off engine
Post by Bear on 08/26/08 at 09:07:21

You don't need to have choke out long enough to wash gas into cylinder. Pull choke at the same moment you hit the kill switch. Use both hands, one on the choke knob. the other on the kill switch. Only takes 1/2 second or less.

Title: Re: big bang when shutting off engine
Post by dasch on 08/26/08 at 09:36:18

I love the fart on shutdown. Reminds me of little babies, burp than sleep :) as many said, lean mixture does it. Or exhaust leak.

Title: Re: big bang when shutting off engine
Post by Lazy Old Rider on 08/30/08 at 04:45:31

It is part of the savages charm ;)

Mine was doing it all the time and my mates on thier big Victories like it cos they know I have arrived.

Proper tuning, the old fashioned way, as described previously will probably improve overall gas mileage, but may make the Lean Mean Environmental Machine raise an eyebrow.

If it can run at tick over slower by adjusting the throttle engine idler screw (left hand side - 'not the right hand under brass plug idle jet')

It may be enough, mine will give a quiet pufft, but if i twist the throttle to simulate fast idle I can give my calling card.

However rather than fiddle with choke on stopping, leave in gear with a bit of "almost biting but slowing the engine grip hill start style, flick the cut out switch, engage neutral. Side stand down cutout to normal remove key. Walk away from bike, return to bike to nswitch off parking light ::)

Title: Re: big bang when shutting off engine
Post by ratdog472 on 08/30/08 at 08:19:28

Good to hear that I am not the only one with the parking light issue.. Puzzles me why it is even there.

I found out the other day when I was leading a couple Hardley Drivensome's around town that the middle rider didn't like the howitzer salute. Actually the comment was made to my wife (she was on the back bike with her dad) asking if I had enough life insurance because if I popped again I was going to need it. Needless to say, I let the howitzer go when we got home.

So ride it, enjoy it, and if it pops every now and then get a laugh out of it.

Title: Re: big bang when shutting off engine
Post by SavageGirl17 on 09/03/08 at 13:30:13

Quote:

I love this part of the movie- and Uncle Buck is so proud!!!

I laugh every time it happens to me. Hey its characteristic. Although, I might have to try some "fixes" to see if I can at least control when it happens (like letting it idle for a few seconds before shutting off)

Title: Re: big bang when shutting off engine
Post by doc5446 on 09/03/08 at 20:53:06

477562757371537D66782523140 wrote:

Quote:

My favorite part of the movie,too...
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Title: Re: big bang when shutting off engine
Post by 07S40rider on 09/04/08 at 08:53:55

I have not tried it yet (because I never remember) but I have heard that if you let the bike settle down to an idle and then let it idle for 20-30 seconds before shutting if off that it will not pop on shutdown.

Title: Re: big bang when shutting off engine
Post by SavageGirl17 on 09/04/08 at 10:09:06

Ever since posting yesterday, everytime I turn off my bike I try the whole "let it idle then shut it down"... works like a charm for me! Only once did I hear a little "phht" and that was nothing. :P
Thanks for the idea!!! (whoever posted that)