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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Stalling at idle problem /cgi-bin/YaBB.pl?num=1485802702 Message started by Alex Wheatley on 01/30/17 at 10:58:21 |
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Title: Stalling at idle problem Post by Alex Wheatley on 01/30/17 at 10:58:21 Hi! New S40 rider here. Also largely mechanical newb. Bike is a 2012 model, 7400 miles (bought at 7100 or so 2 months back). No modifications. In the Piedmont of North Carolina (400ft), so currently a few degrees above freezing most mornings. Since getting the bike, I've had an on-and-off issue of it stalling when I dethrottle to idle. Always starts just fine with the choke in the morning, warms up and idles fine. Some days, that's it - runs beautifully. Some rides, too - even after a bad day - runs beautifully. Most days and most rides, though, I'll get anywhere from one to three stops down the road and when I dethrottle to stop, the engine idles down too far, stumbles and stalls. Sometimes, but not always, there will be a smell of unburned gas while riding, and it will always stall at the next idle when this is the case (too rich mixture?) When this happens, gas will leak out the carb overflow for a minute or two afterwards. The engine will start again without choke if I roll the throttle on about 1/4 OR run the starter for 6-7 seconds, then will usually idle high for a minute then be ok. But then, two stops down the road, it's stalled again and dribbling gas. At present, will start without choke or throttle, but will begin leaking gas from the carb overflow as long as the engine is idling. Given the carb overflow gas leak, presumably the carb is getting flooded. However, turning the petcock to PRIME either before, during or after a stall does not cause any change in the behavior - a stuck float valve would be the obvious culprit, except I'd expect a stuck valve to leak with the petcock on prime... I have also tried adjusting the idle speed, which seems to make no difference. Tapping the carb with a rubber hammer doesn't help. The dealership it was bought from have taken it back in twice. First time they stripped, cleaned and reassembled the carb, and the bike ran fine for them for 3-4 miles, but stalled within 200 feet of my house when they brought it back. Second time, they put 15 miles on it without being able to replicate the problem, so I think they just gave it back to me without doing anything (annoying, of course, that one of it's "running like a dream" journeys would be when the tech was riding it...). It's going in a third time for 7500-mile service in a few days, and I'd love to give them some clear pointers on specific things to check, or things I can try in the meantime. Any ideas? |
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Title: Re: Stalling at idle problem Post by Dave on 01/30/17 at 12:28:18 So......do you still have the stock vacuum petcock? When the diaphragm goes bad....it can allow fuel to flow down the vacuum line and flood the engine with fuel. Read this: http://suzukisavage.com/cgi-bin/YaBB.pl?num=1366651397 |
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Title: Re: Stalling at idle problem Post by Alex Wheatley on 01/30/17 at 12:37:04 I do still have the original petcock (I plan to pop a raptor on there, but given that I've now owned my first bike for, what, two months? I'm hesitant...) - would that cause gas to flow out of the carb overflow line? |
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Title: Re: Stalling at idle problem Post by verslagen1 on 01/30/17 at 12:41:07 I'd clean the carb and put in a new float valve. |
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Title: Re: Stalling at idle problem Post by batman on 01/30/17 at 19:41:54 Alex , your saying carb overflow line ,there are two lines that are tucked up into the backbone of the frame .they should both leak fuel if the bike is upright .are these the lines your talking about?......I think you have a small hole in the rubber diaphragm in the petcock,yes you've only 7000 miles on the bike ,but it's 5 years old which means it sat around a long time with old gas in the petcock . buy a raptor ,change it yourself! buy an adjustable wrench! skip the dealer! they no very little about the care and feeding of the S-40! |
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Title: Re: Stalling at idle problem Post by Alex Wheatley on 01/31/17 at 05:36:40 First - Raptor petcock on order. Service manual arrived yesterday. I suspect I'll still have the dealership do the first few services - I won't feel confident diving into the middle of the engine right away - but the definite medium-term goal is to learn to do it myself. What I'm calling the "carb overflow" is a hose on the very bottom of the bike - which I think is meant to return overflowed fuel to the fuel tank? I was advised to leave it unconnected so that it leaked instead, on the grounds that you'd rather see an overflow than save a few cents on gas. If that's not what I think it is then please correct me! For my own learning: the problem with the vacuum petcock is that if the diaphragm leaks, then it will pull gas from the petcock directly into the intake manifold, yes? And this in turn will make the mixture far too rich, since you're adding extra fuel to the air via the faulty vacuum hose? |
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Title: Re: Stalling at idle problem Post by Dave on 01/31/17 at 05:42:54 Can you take a photo of the tube you are talking about....does it terminate just behind the engine/front of the swing arm? It could be that the tube is the drain for the air box.....and your fuel is flowing into the air box when the petcock vacuum line runs fuel into the carb....or the float bowl overflows. If that is the air box drain....it is not supposed to be a vent or overflow tube - it is the place where un-burned oil from the crankcase vent collects.....and you are supposed to remove the cap and drain the "spooge" when you do an oil change. |
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Title: Re: Stalling at idle problem Post by Kenny G on 01/31/17 at 06:46:09 One of the 2 tubes hanging down from under the engine will be the battery vent if you still have a wet cell battery. Kenny G |
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Title: Re: Stalling at idle problem Post by batman on 01/31/17 at 09:31:14 Dave and Kenny ,are right on! but if you have gas running out this tube it could also be running into your cylinder and down into your oil,I would hold off riding the bike until you change the petcock (drain tht gas from the tank by using "pri" then unbolt the petcock,replace with raptor,it has the same base) then plug the opening on the carb where the vacuum line was,(you can buy rubber caps at any parts store) then check your oil, open the fill cap and if you smell fuel in your oil you need to change it and filter ,you might want to change your air filter as well. If it was suggested to leave the cap off that drain hose by someone at the dealership ,that is a perfect example of them not knowing $hit about your S-40 ! If after you change this you still have the problem ,you have a problem with the carb float or float valve it can't be anything else. |
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Title: Re: Stalling at idle problem Post by Alex Wheatley on 01/31/17 at 09:50:12 Thank you guys! I'll take a photo of the hose I'm talking about when I get home to work out what it actually is. Having now found out where the carb overflows are meant to be, I now know it's not that... (given that it's gas that leaks out, I certainly hope it's not the battery breather ;) ) |
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Title: Re: Stalling at idle problem Post by batman on 01/31/17 at 10:27:59 You should also replace the plug on the air box drain tube,it should not be open all the time,if it is open when the motor is running the carb will pull in air through it and it enters the air box between the filter and carb(dirty) and ruin your motor over time. |
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Title: Re: Stalling at idle problem Post by Alex Wheatley on 01/31/17 at 14:43:09 Ok. Light wasn't too good to get a photo, but I followed the leaking hose up, and it goes into a black plastic box behind the battery (which has two hoses coming out of it). A look in my brand-spanking-new copy of the Clymer's service manual leaves me 99% certain that this black plastic box is the air box (the huge tube coming out if it into the top of the carb might be what gives it away), and that thus gas is indeed leaking into the air box, presumably via the petcock vacuum hose. Raptor petcock should arrive Friday, and of course I won't ride her until then. Oil smells of oil, not gas, and is still amber-colored in the gauge, so I think the oil's fine. Thanks, everyone! Batman - thanks for the heads-up on needing to plug this hose back up again. I'm fairly certain it was open when I bought it, but there is a wire ring around it that looks like it held a plug in place, so I was never 100% sure that it should be open... One last thing though: having now learned where the carb overflow lines actually are, I noticed that one of them curves back over the top of the carb, but the other runs backwards and is tucked under the seat. This second line doesn't seem correct, but I wouldn't really know. What's the best place for these hoses to go?! |
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Title: Re: Stalling at idle problem Post by justin_o_guy2 on 01/31/17 at 14:51:25 A gasoline soaked air filter really messes with how it runs. If you're getting that much gas coming from the carb going into the airbox that it's showing up on the floor,, you REALLY need to fix that and you probably have gas in your oil. |
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Title: Re: Stalling at idle problem Post by verslagen1 on 01/31/17 at 15:14:48 3131276364500 wrote:
both get tucked into the frame above the carb. |
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Title: Re: Stalling at idle problem Post by batman on 01/31/17 at 20:35:25 That "ring" on the drain hose is a clamp used to hold a plastic plug ,but a small bolt would work as well. |
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Title: Re: Stalling at idle problem Post by Alex Wheatley on 02/04/17 at 06:27:29 OK! New petcock is on - and now she feels like a totally different thumpy... Takes longer to warm up to a happy idle now (which makes perfect sense if she was running rich before, I suppose the leak functioned like constant partial choke). Two other observations I wouldn't mind feedback on: 1. She sounds "throatier" than before. The purr has become slightly more of a growl. Why would that be? 2. I have to fill the throttle on a little more than before to get the same response. I can kind of see why this would be the case, but if anyone could explain it I'd be grateful. Thanks all! |
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Title: Re: Stalling at idle problem Post by batman on 02/04/17 at 13:37:19 Alex you've gone from running to rich to the factory lean setting, Your at 400 ft ele.(the closer to sea level the leaner the bike runs) You might consider adjusting your air screw,the white spacer mod, and going to a larger main and pilot jets ,as these mods will make the bike run much smoother and stronger and cooler (lean motors run hotter) (Answers to questions 1& 2) |
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Title: Re: Stalling at idle problem Post by Andy RN on 05/31/17 at 23:22:13 160512130C0107050E51600 wrote:
... I thought those two hoses were "bowl vents" (rather than overflow lines). That's what Savage_Greg called them in these photos: http://suzukisavage.com/cgi-bin/YaBB.pl?num=1098869040/2#2 After reading a Haynes book today, I was under the impression that vents on a carb exist to allow pressure from the atmosphere to enter the bowl, and that it was the difference between the higher pressure from the atmosphere compared to the low pressure of vacuum created by the venturi that created the force to suck the fuel up into the carb. That was my interpretation of a "vent" line. Do those vents also act as overflow lines, or am I somehow misunderstanding something here? Thanks! |
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Title: Re: Stalling at idle problem Post by justin_o_guy2 on 06/01/17 at 06:41:47 They are vents. Gas Can come out of them, IF you have a problem. |
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Title: Re: Stalling at idle problem Post by Dave on 06/01/17 at 08:44:33 If you turn your bike on it's side, or even upside down.....the vents do become drains! The air needed by the carb for the atomization of fuel comes through the air jets, and it is filtered air and it is provided by passages in the inlet throat of the carb. The fuel being used out of the float bowl is being replaced by the fuel flowing into the float bowl through the fuel line/float needle/seat. There isn't really any kind of air flow through the float bowl when the engine is running. When you shut the engine down, or park the bike in the sun, the liquid fuel in the float bowl needs to have a vent so the fuel vapors can go somewhere......and that is what the vents do. |
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Title: Re: Stalling at idle problem Post by Andy RN on 06/01/17 at 10:56:12 6D565B4C5D514A4C575F524D3E0 wrote:
So I don't have to worry about flooding the carb when I'm doing barrel rolls ;) |
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Title: Re: Stalling at idle problem Post by batman on 06/02/17 at 22:01:59 If the barrel rolls are fast enough centrifugal force should keep the fuel in the bottom of the bowl,vents are not needed! ::) |
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Title: Re: Stalling at idle problem Post by Alex Wheatley on 06/03/17 at 09:54:25 58636E7968647F79626A67780B0 wrote:
I'd been vaguely wondering why I always smelled gas when it'd been parked in the sun (and it lives outside in North Carolina - it's in the sun a LOT right now). I'd figured it was probably a vapor leak out the fuel filler cap, but this also makes sense, and explains why I could never quite track the smell down if it's coming from (a) under the seat and (b) on top of the engine. Good to know! |
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Title: Re: Stalling at idle problem Post by justin_o_guy2 on 06/03/17 at 10:47:42 I saw a cigarette lighter trace a smell back to the source once, when I was in the eighth grade. He was a bit stunned when the next stench in the air smelled Exactly like burnt hair. |
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Title: Re: Stalling at idle problem Post by norm92de on 06/03/17 at 14:25:19 When I parked my Triumph for a month or two the fuel consumption was greater than normal due to the evaporation from the tank and two carbs. |
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