|
SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Annoying carburettor behaviour. /cgi-bin/YaBB.pl?num=1496795234 Message started by eau de sauvage on 06/06/17 at 17:27:14 |
|
Title: Annoying carburettor behaviour. Post by eau de sauvage on 06/06/17 at 17:27:14 OK, I do understand that blipping the throttle causes the engine to die because it's going fast enough to suck fuel in but no fuel is coming. I sort of accepted this even though it doesn't happen on my gs500, in fact one particular method of testing the carburettor is to bring the revs up to a few thousand and then shut it down and the engine is supposed to quickly drop back to idle with no wandering. This is how it behaves on my GS which is a similarly archaic machine. Blipping the throttle on the GS no matter how aggressively will not shut the engine down. So why does it not shut the engine down on the GS but it does on the S40. I've raised the idle when hot speed to 1300 in order to try and avoid this. Occasionally if I'm not careful the engine will die and I've sort of gotten used to it and it does not happen very often now. This is how it's been since ever. However yesterday I have discovered that this could in fact be a life threatening problem. I'm about to install some new front brake pads which have lasted a surprisingly long for OEM's 12,000kms this seems to be about double the 4000 miles I've seen reported. Anyhoo so before installing the new pads I thought I'd practice some emergency braking on the old pads so that after the new pads are broken in I can see if there is a difference in emergency braking with better quality pads. This is when the aforementioned life threatening problem manifested. OK so I'm tooling down the road at a decent speed, not too fast but fast enough to test the stopping power, at about 80 km/h shut the throttle, remain in gear grab a handful of brake and just before I come to a stop I pull the clutch in but the engine dies. This can be problematic if someone is coming up behind me and I need to take off quickly. In fact this is the very reason that we are urged to remain in gear during an emergency brake. Do other people have this problem? How do you solve it, do you put the idle speed up even higher? Running a 52.5 pilot. |
|
Title: Re: Annoying carburettor behaviour. Post by Kenny G on 06/06/17 at 17:56:48 Sauvage, I think if I had the symptoms that you have I would start looking for intake leaks. Check where the manifold fastens to the engine and inspect the o ring that is used for a gasket and put a bit of lubricant on the o ring before gently tightening the bolts Perhaps I would take the boot off between the engine and carburetor and clean all the mating surfaces and make sure everything is properly seated before tightening the clamps. Kenny :-/ |
|
Title: Re: Annoying carburettor behaviour. Post by justin_o_guy2 on 06/06/17 at 18:00:52 You're not downshifting and working the throttle and brakes together? |
|
Title: Re: Annoying carburettor behaviour. Post by eau de sauvage on 06/06/17 at 18:01:49 OK I'll give that a go, by 'manifold' are you referring to the header pipe and the crush gasket? |
|
Title: Re: Annoying carburettor behaviour. Post by eau de sauvage on 06/06/17 at 18:03:19 Yeah I do that when riding normally but not during an emergency braking procedure. 534C4A4D50576656665E4C400B390 wrote:
|
|
Title: Re: Annoying carburettor behaviour. Post by justin_o_guy2 on 06/06/17 at 18:04:55 342B2D2A3730013101392B276C5E0 wrote:
If you're still in fourth gear and you're grabbing brakes and the clutch is engaged, You Killed the engine. |
|
Title: Re: Annoying carburettor behaviour. Post by Dave on 06/06/17 at 18:28:41 If I do an emergency stop and grab the brakes and clutch and chop the throttle instantly.....the engine may stall, and often does. It is a situation that does occur as the engine just isn't getting enough fuel when the needle drops into the jet and the only fuel flow is the Pilot jet. On your GS with multiple cylinders it just isn't as likely to happen....maybe it has something to do with the engine size vs. the carb size....not sure. I don't think the Dial a Jet will help if you installed one - as it is on the air filter side of the slide. Can you get any "pure" gas in your area that doesn't have ethanol mixed in? That might make the TEV circuit more helpful as the ethanol runs a bit leaner than pure gasoline. Also make sure your TEV is clean and the diaphragm isn't stiff - as they age the diaprhagm becomes stiff and the TEV doesn't work as well. |
|
Title: Re: Annoying carburettor behaviour. Post by eau de sauvage on 06/06/17 at 19:19:50 @ Dave, this is Australia, land of Mad Max, non ethanol is everywhere, it's a fuel with ethanol that harder to find! So if you're telling me that this is perfectly normal behaviour I can't argue because I have not ridden that many bikes, but I've never encountered a bike that stalls as easily as this S40. I mean I don't even have to blip the throttle all I have to do is raise the engine speed to about 3000 and then shut the throttle too fast (with the bike in neutral or the clutch in obviously). What I've been trying to practice is trying to shut the throttle quickly but without just snapping it shut instantly, but I'm not having any luck with that. It's something that I'm constantly reminded of though because here in Queensland cars really like to tailgate so it's something that you have to be always vigilant about. I see heavy trucks all the time sitting on car length behind a car while traveling on a 4 lane motorway at 100kph. @ Justin, If you're still in fourth gear and you're grabbing brakes and the clutch is engaged, You Killed the engine. I'm not sure what that means! But to clarify, I don't pull the clutch in till the bike is close to stopping so that I can use the engine braking as well. I just grab the clutch at the last moment so the engine won't stall. This is why this puzzles me, because by the time I hit the clutch the engine is not going fast any longer. |
|
Title: Re: Annoying carburettor behaviour. Post by justin_o_guy2 on 06/06/17 at 19:25:00 You need to downshift and keep the engine spinning over. Can you Drive with it in fourth gear and ten MPH on the speedometer? You're killing the motor with the brake if you don't downshift. |
|
Title: Re: Annoying carburettor behaviour. Post by batman on 06/06/17 at 20:10:47 I don't believe you have much engine braking in fourth gear,ie. if you just close the throttle in fourth gear without braking how fast does the bike slow down ?(not very) that's the amount of engine braking you have!You should just pull in the clutch and brake you'll stop faster not fighting the inertia of the motor,( your using the brakes to stop the motor and the bike ,when you need only to stop the bike! the motor will slow by itself, when you use the brake without pulling in the clutch you slow the motor faster than normal, as the piston slows it draws less vacuum ,therefore less fuel through the TEV and the pilot jet and has more of a chance of stalling!)you can be down shifting with the clutch in so if you need to speed up you'll be in the proper gear so you won't be lugging ,your acceleration will be crisp.Even if you stall,if you've down shifted all you need is to hit you starter button and be instantly on your way. I don't thing it's the bike's fault, as much as you driving it funny.I don't know where you got the idea that braking with the motor engaged would allow you to stop faster but it's incorrect. |
|
Title: Re: Annoying carburettor behaviour. Post by Dave on 06/07/17 at 02:03:10 716E686F72754474447C6E62291B0 wrote:
The issue he is having is not with a normal reduction in speed that provides you with the opportunity to shift gears and slow down casually. His concern is in an "emergency stop".....you are cruising along at 60 mph and you need to stop "NOW"! So you chop the throttle and pull in the clutch....and apply the brakes as hard as you can. The engine has instantly gone from 4,000 rpm to a closed throttle (There is no time to downshift while you are doing everything you can do to stop and avoid locking up a wheel or hitting the deer/car/truck/moose). Under these conditions, the engine can stall and I don't know anyway to change that condition. Once the emergency is over you have to hit the starter button and then once the engine re-fires you downshift 3-4 times to get in the correct gear - or you are stopped and you need to rock the bike back and forth while you downshift to 1st gear. This scenario sometimes happens, and eau de sauvage is doing a really good thing by practicing it - he will know what to expect when it happens for real. |
|
Title: Re: Annoying carburettor behaviour. Post by eau de sauvage on 06/07/17 at 02:47:31 @Dave, OK you've answered this to my satisfaction, it's just something that I guess I'm going to have to live with. But it's still a worry. Whenever I hit the brakes even under the most innocuous condition I reflexively look in the rear vision mirror first. As you probably might know Adidasguy, Patrick Lajko who has posted many GS500 youtube video was rear ended and killed while waiting at a stop light. Whether he was well stopped or whether he had just stopped I do not know, but it's something that I've always been wary of. You're right about the emergency braking, I've seen lots of threads about it but many people seem to not really understand the 'emergency' bit. There's very very fast braking and then there's 'stop now or die' braking, it's the latter I'm referring to. This was drummed into me at a stay upright course over 30 years ago, which I detail in this thread... http://gstwins.com/gsboard/index.php?topic=71318.20 |
|
Title: Re: Annoying carburettor behaviour. Post by Steve H on 06/07/17 at 04:45:42 Mine never stalls when chopping the throttle. Sometimes the revs might sag a little but it doesn't stall. |
|
Title: Re: Annoying carburettor behaviour. Post by batman on 06/07/17 at 06:49:00 If your stalling when you chop the throttle closed ,it maybe you need to go to a larger pilot jet ,or check and clean your TEV valve. Many people have posted that they can't get their bikes in 1st gear from being in neutral at a stop,and I've advised that you should never be in neutral for danger of being hit from behind ,and not having the option to instantly move out of harms way. |
|
Title: Re: Annoying carburettor behaviour. Post by IslandRoad on 06/07/17 at 13:14:02 Eau, I had the same problem with my bike. Then I read on the forum about the various idle speeds that guys on here set their bikes to - anywhere from 1100rpm - 1500rpm. I originally had mine set to about 1250, and would experience the problem you described. I upped ithe idle to 1400, and the problem seems to have been resolved. As a bit of background; when I was tuning the carb (warm engine) I tested the lower threshold of the idle by giving it a bit of throttle and then chopping it, while The bike was stationary and in neutral. The bike would stall if the idle was below 1250. So I took that to be my minimum idle speed. Given the problem with cutting out, on the road, in emergency braking situations, I figured my minimum idle speed needed to be higher to account for that possible scenario. As I mentioned, so far so good. |
|
Title: Re: Annoying carburettor behaviour. Post by batman on 06/07/17 at 13:39:27 OK lets take braking to the extreme! He chops the throttle ,hits the brakes as hard as possible ,but doesn't pull the clutch in .Lets say he applies the rear brake to the point that the rear wheel stops or skids. What rpm is the motor turning at that point? the same speed as the rear wheel ! ZERO! I 'm a little slow sometimes but I think most people would call that stalling.If you want to stop ,with a chance of not stalling squeeze in the clutch and brake at the same time! Instead of wasting the already limited power of the rear brake to stop the motor and the rear wheel from turning ,the braking force can be applied to the rear wheel alone ,stopping you faster. It's not rocket science,it's logic !I f your leaving the clutch engaged to prevent rear wheel lock up ,it might be better to adjust the brake cable to a point where you can hit the brake as hard as possible without lockup and not have to be worried about it's use in panic stops. |
|
Title: Re: Annoying carburettor behaviour. Post by justin_o_guy2 on 06/07/17 at 14:22:12 Because the clutch is engaged, the engine turns the rear wheel. Using the brake to slow the wheel slows the engine. Can you have it in fourth at ten MPH? Zero? You will kill the engine if you do a stop with the clutch engaged. Do Everything you do when you practice a panic stop, but don't go fast. Do it once you hit fourth, just APPLY brakes, don't grab the clutch. See if it dies. Slow down, jam on the back brake Just like you have been. |
|
Title: Re: Annoying carburettor behaviour. Post by IslandRoad on 06/07/17 at 15:16:06 Eau, I just re-read your first post (after reading Dave's responses). I assumed you were pulling the clutch along with the brake. I agree with Dave. It sounds like your stalling the bike. |
|
Title: Re: Annoying carburettor behaviour. Post by IslandRoad on 06/07/17 at 15:19:04 There is emergency stopping for when you want to avoid impact, then there is emergency stopping for when you need to minimize an unavoidable and inevitable impact. For the latter, I don't think staying in gear is gonna matter. |
|
Title: Re: Annoying carburettor behaviour. Post by Dave on 06/08/17 at 02:01:54 This subject appear to be very similar to an oil thread....or one on countersteering - there just doesn't seem to be a universal agreement on the subject. Just do what works the best for you........ In the "panic" stop that requires you to brake at the absolute maximum level.....leaving the bike in gear under full braking will most likely cause you to either stall the engine as you brake as hard as you possibly can and say in control - or it will increase your stopping distance as you must also overcome the momentum of the spinning engine at the same time you are slowing the bike down. In a 60 mph to 0 mph stop you are traveling at 88 ft/s, and they claim the reaction time will use up 132 feet ....and the braking will require 172 feet - all of this in less than 5 panic filled seconds. You don't have time to start downshifting.....and at some point you have to pull in the clutch as your speed drops toward 0. In that scenario.....my engine will likely have stalled in the process.....and I really don't care as I have other things on my mind in that 5 seconds. When the emergency is over I hit the starter button - and continue on my way (hopefully). I realized that my comment on my engine stopping likely is not a good indicator about what should happen on a stock engine/stock CV carb bike. I set my carb jetting up using an oxygen sensor, it runs great and has a nice tan spark plug, and it is tuned properly. I have a VM round slide carb, bigger cam, Wiseco piston....and what my engine does may not reflect very well what the stock engine will do. The CV carb does have the TEV to help correct the lean condition that is created when you allow the throttle to close fully under high vacuum conditions - and it likely does do some good when it is working well. |
|
Title: Re: Annoying carburettor behaviour. Post by Eegore on 06/08/17 at 09:50:26 This might be a little off-topic but I didn't think this warranted a whole new thread. Can a carb be tuned then removed, a new carb put on for a while, then have them switched back without the first one needing to be completely reworked again? |
|
Title: Re: Annoying carburettor behaviour. Post by ohiomoto on 06/08/17 at 09:59:20 Yes, but if you make any other modifications to the intake, exhaust or engine, you might need to retune the first carb. |
|
Title: Re: Annoying carburettor behaviour. Post by stewmills on 06/08/17 at 09:59:31 1C3C3E362B3C590 wrote:
If no other variables in the bike are altered, why not? If you change anything such as exhaust, air filter, etc. you can expect to need to make adjustments to accommodate. Moving from one location to another (considerable change i elevation) could warrant adjustments. In some places summer versus winter have drastic enough changes in air density and temperature to warrant slight adjustments. I think the answer is YES, but that all depends on how long it sits on the shelf and what happens by the time you reinstall it. |
|
Title: Re: Annoying carburettor behaviour. Post by ohiomoto on 06/08/17 at 10:02:09 LOL beat you to it Stew, by seconds! |
|
Title: Re: Annoying carburettor behaviour. Post by Eegore on 06/08/17 at 10:05:07 I doubt it would be long. I will have one tuned by someone that knows how and I will try to do it on the second carb. The bike wont have any changes made however there might be a significant altitude change depending on where I am at the time. I just like to have a spare part in case I damage things, and I try if possible to keep a third in stock. |
|
Title: Re: Annoying carburettor behaviour. Post by stewmills on 06/08/17 at 11:38:45 6F68696F6D6F746F000 wrote:
Do you mind checking with me first next time? >:( ;D ;D ;D ;D ;D |
|
SuzukiSavage.com » Powered by YaBB 2.2! YaBB © 2000-2007. All Rights Reserved. |