Bandit Alley
GENERAL MOTORCYCLE FORUMS => GENERAL MECHANICAL & TECHNICAL => Topic started by: rider123 on November 01, 2005, 02:54:43 PM
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Hello I seem to have a ever so slight stumble just off idle at very small throttle inputs. My bike is a 2005 B1200S with stock everything and I haven't pulled the plugs off the carbs at least untill either the warranty period is up or my first 1000kms service. I don't have the manual yet :sad: but I know just from the specs that the compression is low enough that I don't need high octane gas. I've been filling up with med grade (89) as a pre-caution untill I get some sort of verification from the manual that regular gas is ok. What I'd like to know is:
1. Could the slight stumble be caused by the octane being higher than a recomended 87? If the gas is slightly less "burnable" very slight throttle inputs would exagerate the problem. Personally, I don't think this is the problem but I like to explore all the angles. Is regular gas ok? I may try a tankfull and see if it helps.
2. Jetting, I understand that these bikes leave the factory slightly lean to try and slip by the facists at the EPA. When the stumble comes on at the specified throttle input, it works fine for about 2 secs then slightly stumbles then works again for another 2 secs. What I'm thinking is that when you first put the throttle so that it will stumble the carbs are already primed and ready to go from normal throttle inputs as you demand slightly more gas at low rpm(<1500rpm) there isn't enough vacuum to draw that teeny tiny little bit of exta gas through the pilots to get you over the hump. It seems that only one cylinder is not getting enough juice to get over this hump so normally you could experiment by backing off 1/8th of a turn on each cylinder to see if it helps once you find which cylinder is slightly lean you just give it that little teeny bit of extra gas it needs and you're good to go. Or if you want to play it safe just turn all the pilots out an 1/8th of a turn and it usually cleans up any carburation issues and may give you better throttle response. But due to the EPA wanting to be our mommies :duh: we can't do this very minor and nessesary adjustment without voiding warranties and such. Once over the "hump"(>1500rpm) vacuum takes over and there is no stumble at all. So I feel this is a very minor problem. It also has been cold and sh!tty so who knows maybe in the summer it's perfect.
3. Carb Sync, this is the easiest explaination. One cylinder is synced slightly less than the other and is not pulling it weight. This slight mal-adjustment would be exaggerated at low rpm and low vacuum. This would be fixed at the 1000km service. When I received my bike is was super crappy outside and the dealer told me that the mechanic took it only for a very short ride so this mal-adjustment might have gone unoticed because unless you were specifically looking for it you would never notice it at all.
As I said it's extremly minor and I only noticed it in the last little while. If you put someone on the bike who's never ridden it before I'd wager he wouldn't even notice it. If it is a jetting issue it's so slight I can wait untill the warranty period is up and by then I'll be probably looking at slip on's and jet kits anyway. Thanks for any input.
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I'd go with the carb sync first.
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My thoughts exactly, first simple then more complicated. If the dealership didn't take it out for a proper test ride they probably didn't test the thing properly and figured if it rode ok they could fix it at 1000kms. I'll put in some regular gas just to eliminate that option.
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Is it maybe the TPS sensor off? I'm going to check tomorrow check out my TPS instructions post. It supposedly affect low throttle opening timings. Possibility? I'll post what I find if possible.
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I doubt it's the TPS on a new bike. I have the same problem on a fairly new '03 with 4300 miles on it (Piped & jetted)
I''m pretty sure it's the carbs out of sync. It's just an infrequent slight stumble that no one would notice except me. Seems to happen most after I'm sitting at a stoplight for a long time. (Like over a minute or so.) The other 99.9% of the time it pulls like a mutha from idle to redline.
Also, I kinda 'wrecked' my original carbs trying to get them out and jetting them. I was lucky enough to get a complete new set (less than 100 miles on them) on Ebay in perfect condition, but who knows where the syncing is on them.
Carb syncing is one of the things on the 'to do' list after the first 600 miles or so. I've yet to do it on mine.
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Good advice Paul, I'm going to wait regardless untill the first service, as it's a new bike things get stretched, pulled and moved out of adjustment. That's why the first service is very important. I will measure the TPS tomorrow because it is so easy to do. If it's out of alignment or mal adjusted I may even just leave it like that untill the first service. I'm just asking to be for armed with as much knowledge as posssible so the dealer can't give me any BS whcih we all know some dealers like to do. For-warned is for-armed. I'll post any info I have for the benefit of other people who may be having the same problem.
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I vote for a "lean stumble" caused by the mixture screws being too far in.
Removing the limiter caps and backing them out 1/2 turn should cure the problem -- it did on my 2003 Bandit 1200.
The TPS was way off but it didn't cause the stumble, rather it was the cause of poor gas mileage. After the mixture screws were opened a half turn I then turned attention to the TPS.
There's a fairly good description on this site in the General section with several people (myself included) offering suggestions and how-top advice.
Of course carb synch will be the finishing touch and will probably result in smoother low speed running if it was off a bit from the factory.
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You said you don't want to mess with it right until the warranty is up.
But I'll second what Ray said... go ahead and drill out those plugs and give the A/F screws a 1/2 turn out. They are probably the most idle & off-idle related part of the carburetion... and they are set too lean from the factory.
Regardless... let us know the results of your TPS measurements.
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Sorry to be repetitive...but I'll "third that"...my '03 1200S did the same thing until I drilled out the carb mixture screw plugs and readjusted them. They are now about 3 1/2 turns out. This act does not void the manufacturer's basic warranty!
Eddie
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I vote for a "lean stumble" caused by the mixture screws being to far
I agree with you, just about all new bikes come on the lean side, and with cooler weather they will really be on the lean side.
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Thanks guys good advice, on a "normal" carb I would have marked the stock settings and backed it out a 1/4 or half turn by now, but with these "new improved EPA carbs" it's a real pain in the ass. I don't know what those crazy hippies at the EPA were smoking but cmon!! Later in the week it's going to get semi-summer like weather (68 degress) so at least when she's warmed up I'll be able to tell if it gets less noticable. As I said you'd have to really look for it as is to notice. Also I did a quick check of my TPS but forgot to put my Ohm meter at a better resolution here are the specs:
Ohm 1 reading throttle closed---> 5.1K Ohm
Ohm 2 reading throttle open ----> 4.2 Ohm <-----should be 3.9K!! out of wack right out of the factory!!
I'll fix the TPS tomorrow and see for fun if it helps, I know it does affect slow speed low throttle input running so who knows, it's good to have it properly adjusted anyway. If I'm guessing right the TPS "thinks" I have more throttle on than I do so maybe it's making the timing slighly off.
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Help me out here guys. Too lean means too much air, not enough gas in the mixture right? So backing out the screws to make it "richer" reduces? the amount of air flow into the mix?? Am I getting this right? Why is this so confusing??
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Help me out here guys. Too lean means too much air, not enough gas in the mixture right? So backing out the screws to make it "richer" reduces? the amount of air flow into the mix?? Am I getting this right? Why is this so confusing??
Out (Counter-Clockwise) = Richer
In (Clockwise) = Leaner
I believe turning them out increases the fuel intake rather than decreasing the air intake.
Someone feel free to correct me if I'm wrong.
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No you got it right, think of a gate on an irrigation ditch, you raise the gate and more water goes through. Close it up and less goes through.
My bike now, brand new 2005 needs more juice. It comes very lean from the factory. It would be great for the Ho chi Mihn trail or a tropical rainforest but not Canada. I'm going to get them to drill out the plugs at the 1000km service and back the pilots out a 1/4 - 1/2 turn. The sad thing is that's all it needs to drive beautifully. Today it's 18 degress and the bike runs slightly better due to it being slightly richer so I know for sure thats what it is.
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Ok, here's the thing: I believe my B12 has been rejetted since the caps are missing from the mixture screws and it has a full Yoshimura exhaust, along with the fact that the guy I bought it from said it was. It takes off very nicely with a lot of throttle. But with just a little bit of throttle, it kind of gurgles and sputters a tiny bit. But, no matter where I'm at on the throttle, when I let off, it pops a lot. But, acceleration is very smooth and throttle response is very quick and even. So, that being said, would trying to adjust the mixture screws accomplish anything for me? I've already checked and reset the TPS to the magical 76% thing night before last which didn't seem to have any effect on the aforementioned problem. Would I need to go up a size on the idle jet? Any ideas?? :banghead:
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The sad thing is that's all it needs to drive beautifully.
Well... almost.
Add slip-on exhaust and a Stage 1 jet kit... then it's beautiful. :wink:
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Ok, here's the thing: I believe my B12 has been rejetted since the caps are missing from the mixture screws and it has a full Yoshimura exhaust, along with the fact that the guy I bought it from said it was. It takes off very nicely with a lot of throttle. But with just a little bit of throttle, it kind of gurgles and sputters a tiny bit. But, no matter where I'm at on the throttle, when I let off, it pops a lot. But, acceleration is very smooth and throttle response is very quick and even. So, that being said, would trying to adjust the mixture screws accomplish anything for me? I've already checked and reset the TPS to the magical 76% thing night before last which didn't seem to have any effect on the aforementioned problem. Would I need to go up a size on the idle jet? Any ideas?? :banghead:
It sounds like you may want to give the pilots a 1/4 or half turn out just to find out. The best idea is to mark where the jets are now so you can go back if you get into trouble. Try little adjustments first. Say 1/4 of a turn which is very minor then see what happens. Remeber always mark where it is now so you can go back. If it seems to get slightly better with a 1/4 turn, try another 1/4 turn, or if you want to be super safe. Do 1/8's of a turn. As long as you have the original settings marked you can safely experiment a bit. I'm sure someone with more knowledge here can give you even better advice.
As far as I know the popping is an indication of slightly leaner mixture(closed throttle) or an air leak in the exhaust. Because of your sputtering/hesitation, I would go with the pilots needing a little tweaking. Hey, it's free!! Give it a try.
As far as my bike is concerned I KNOW that the pilots are too lean. If you give it a bit of throttle at low RPM it just goes bwaaaah! With on occasional PUFT! instead of accelerating normally. Once it's one the mains though > 1500 rpm it pulls very strong with no hesitation. It boggles the mind why Suzuki would do this to a nice bike such as the bandit!
As far as the TPS goes it smoothed out the entire bike and helped the problem because mine was out of wack from the factory. But no amount of timing precision is going to help lean jets. At least I found out a way to measure the distance between the plugs and the mixture screws. The plugs have a hole in them at least on mine so you can stick in a sewing needle or other thin piece of steel then using a magic marker mark the edge. When you pull it out you have the depth from the top of the plug to the screw. So when you put the tape on your drill to drill them out I suggest giving yourself an extra couple of mm's or two to make sure you don't screw up the heads.
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Thanks rider, I'll try finetuning the mixture screws along with checking for exhaust leaks.
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Well I've had enough of this crazy stumbling and whatnot. I called the dealer and talked to the service department. He seemed like a nice guy and even though I'm early(500kms not 1000kms) for the first service he said it was good to come in and they would definatley get rid of those horrble pilot screw plugs and fix the carbeuration and anything else needed looking at. With today being around 65 and sunny the stumbling has improved obviously but boy they sure do come lean from the factory!!! Once it's on the main jets though it's fine. I figure Suzuki must be playing some sort of cat and mouse games with the EPA or whatever made them put these silly plugs on in the first place.
This must be the conversation at Suzuki:
"Well if we make the bandit 1200 run properly the EPA will be all over us, what do we do? I know we'll lean out the mixture on the pilots to reduce overall emmisions throw some easily drillabe plugs on there but make the mains ok so if you juice it or above anything but idle it will work. Once it's left the factory it's not our problem anymore"
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Well I got it back from the dealer and they did drill the plugs and fattened it up a bit so its much better but still a little lean if you ask me. At least the caps are off so I can fix it myself. Still a bit of a stumble but not half as bad as before and at least it's not misfiring due to it being so lean from the factory!
Although maybe it's not the pilots. If I give it just a bit of throttle to take off slowly from off idle there is no problem, but if I give it just slightly more(1/8th throttle maybe?) it starts getting mushy. It's weird, does this mean it still needs some mixture fattening? Or does it need a little shimming? When on the mains it's fine so my guess is the mixture screws. What do you think?
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It's weird, does this mean it still needs some mixture fattening? Or does it need a little shimming? When on the mains it's fine so my guess is the mixture screws. What do you think?
Ivan's or Dale's Stage 1 jet kit. Cheap & Effective.
Or... just putting a couple shims (radio shack washers) on the needles should make a difference for you with the stock can.
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Well I'll probably look at aftermarket cans and jetting next year, it's just very bizarre to me that Suzuki would take one of their most popular selling bikes and make it demented right out of the factory. On the weekend it's going to be 14 and sunny so I may try turning out the mixture screws a little bit more after I mark where the dealer set them to. I have a feeling that the dealer would probably be very conservative on any adjustments so as to not boost emissions up too much. It's getting as good or better gas milage it seems than my 750EF with a Yoshimura pipe so I have a feeling it's really lean. Ironically, once on the mains it drives perfectly. Very very weird Suzuki!!
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Keep in mind that it's also about $2000-$3000 less than any of it's competitors. They gotta cut corners somewhere.
And it's not a popular bike really... it's an inexpensive UJM that isn't even available in the U.S.A. anymore after this year because of slow sales. I got mine new in '04 for $6500 out-the-door. Nothing else came close.
But put a few $$$ and it's as good as anything on the road, IMO. There is no shortage of quality, inexpensive aftermarket parts to make it 'world-class'.
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Yeah maybe you're right it's popular here in Canada and VERY popular in Europe more than the States. I don't mind that it needs a bit of tweeking coming out of the factory but covering the plugs and jetting it very lean out of the factory is just weird if you ask me. I guarentee you once I get to those mixture screws tomorrow its going to clean up the last little bit of stumble off idle. I don't mind doing it, but at least they should allow me to!! THank god the dealer left the plugs out. Thanks for all your guys help.
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I don't know how long Canada has been going with the US emissions standards, but US carbs have had "tamproof" adjustments for DECADES - as part of federal regs. This is why US B12's don't have adjustable needles like their European counterparts - as well as the pesky plugs on the mixture screws... and why there's a big market in jet kits.
The excessive lean condition is also a finction of getting it to pass US EPA emissions standards.
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Wow! Decades? Hmm must be a new thing here then. Ever since NAFTA Canada has been trying harmonize things with the States to make it easier for standards and such. I guess this was one of those things that wasn't "easier" :grin: Still no harm done at least I can fix it now. Because it's semi-cold I won't go too crazy untill the spring, maybe 1/4 turn shouldn't be too much. Although just from this board people seem to have positive results and reviews of the holeshot jet kit and others but I'm not sure it would really help with just the stock muffler so I'll hold off for now.
Here is from Fastlarry's site on pilot screw adjustment:
# Adjusting the Pilot Screws
* Warm the engine to full hot with a 15-20 min. ride.
* Using a hand held tachometer or deft ear track the idle rpm as you turn out (counter clockwise) the pilot screw on one carb. Slowly turn out in 1/8 turns until idle rpm rises no more. Adjust idle speed to spec (1200rpm +/- 50). Repeat this step for all carbs.
* Turn in the pilot screw on one carb until there is an idle drop. Turn it back out 1/8 turn. This is your lean-best idle. Repeat for other carbs.
* You may need to enrichen slightly if you still have an off-idle stumble when full hot.
It makes sense to me any thoughts?
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Wow! Decades?
Yep...In the US, the big Hondas (most familiar to me) stopped using adjustable needles in 1978 (unless manufactured in 1977 or earlier). The use of pilot plugs and limiter caps were fully implemented by 1980, as were plastic non-adjustable floats and non-threaded pilot jets (they were pressed into place). All this was to comply with the US EPA "tampering" laws.
Eddie
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Well I fooled around with the mixture screws a bit and it didn't seem to change the idle at all. It's at night so I only turned one turn either way. Hmmmm......Maybe I've maxed out my pilots screws? I'll count the turns tomorrow and see. Or it may be that it is affecting idle but I can't hear any difference as it's slight. I guess what I could do for fun is put the mixture screws out a 1/4- 1/2 turn and see what happens. I'll mark where it is now so I can go back.
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Ok well I turned it out a half a turn to richen up a bit and everything seemed ok but occasionally I get this. Sometimes, I'll blip the throttle at idle and the idle will go down to 1000 rpm then back up again to 1250 where I have it set. It seems to be more previlant at full hot. Maybe a tad too rich? It's intermittant, usually if I stay at idle for a while. It almost as if one of the cylinders it slightly rich. It weird, it idles fine, nice and steady but still is slightly mushy off idle not much now though. I may just bite the bullet and take it to someone other than the crappy dealer. Just for reference on a 2G bandit, the standard screw turns out from stop are 2.5-3.0, is that correct?
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More like 2.0-2.5 for a bone stocker.
When I installed my jet kit, I found 'em all over the map from 0.75 to 2.25.
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Woah that is all over the map. Fast Larry's site says for the 15 pilot jet it's 2.5-3.0 turns out. In the Haynes manual It stipulates 3.0 turns out. Since mine was experiencing a slight lean stutter I backed it off another 1/8th. THis way if I need to go back to totally stock (3.0) it is very easy. already it's starting to run better just at idle and reving parked with only the outer carbs set to 3 and 1/8th. When I get home(and have tools) I will set the inner carbs to 3 and 1/8th out so that they are all the same and start there. I think I can get over the hump with a little experimentation. Who knows how weird the originals were set up as. I have a feeling the dealer set them to the absolute minimum for emmisions reasons (2.5) or maybe not at all. I can't believe I'm making it better by myself. I thought they were experts with real tools and exhaust sensors, etc. Well I guess the old saying "If you want something done right...." applies here. I let everyone know how it turns out. I'm going to make the bike slightly lean as it is colder outside so when it gets warm outside it won't be crazy rich. If I do figure it all out I'll post my experiences as I have a new bike so it may helps someone else avoid some frustration and hassle.
Edit: Well before I went home from work I thought I'd try the jets at 3.0 turns out which is stock on the two outer carbs. Wow what a difference. Obviously it's still a little weird because I couldn't get to the two inner carbs but it's alot better even though the temp is just over freezing and a little wet(scary drive!). So if the bike is running much better on two carbs at stock, hopefully it will be good on all 4 running stock. I think it will be a good starting point to tweak out any weirdness. I will probably leave it on stock untill next spring when I can tune it properly. However if running it 3 turns out is stock acording to Haynes and Fast Larry's site. What does the EPA consider "stock"? Also where was it before I got a chance to fix it? Where did the dealer put it? Strange....
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Well 3.0 turns out seems to be the magic number, while slightly lean there is no stumble or anything like that. The idle now is slightly erratic but still ok. On the weekend I will try the best idle method on the pilots then I have to say it's fixed. It's only slightly lean now with it being really cold outside so I'm hoping when it warms up it in the spring it will be perfect. In the Haynes manual the US/UK use the same pilot jet screws and the manual lists the UK model (where its cold) as 3 turns out but lists the US model as "PRE_SET" it would be interesting to find out what it's preset to. I doubt it would be 3 turns out, one gentleman said his were set from .75 (!!) to 2.5 after he got the caps off. Talk about a difference!
Update: I've been thinking that the bike might even be a little rich it runs great cold to almost warmed up then gets a little sloppy when full hot. When I start the bike and let run a bit(no choke still warm enough to start) I can smell the faintest hint of fuel. As soon as its full hot you can't smell it anymore. Getting closer guys!!(finally, holy!)I'll turn her down an 1/8th at a time untill I figure she's really close then do the "best idle method".
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I doubt it's the TPS on a new bike. I have the same problem on a fairly new '03 with 4300 miles on it (Piped & jetted)
I''m pretty sure it's the carbs out of sync. It's just an infrequent slight stumble that no one would notice except me. Seems to happen most after I'm sitting at a stoplight for a long time. (Like over a minute or so.) The other 99.9% of the time it pulls like a mutha from idle to redline.
Also, I kinda 'wrecked' my original carbs trying to get them out and jetting them. I was lucky enough to get a complete new set (less than 100 miles on them) on Ebay in perfect condition, but who knows where the syncing is on them.
Carb syncing is one of the things on the 'to do' list after the first 600 miles or so. I've yet to do it on mine.
I had a few furrin' cars with vacuum slide carbs on them, just like our Bandits use. I soon found out that it was a good idea to get one 'o them-thar vacuum sync-ing things that slapped over the carb's mouth in order to establish whether or not the whole bank of carbs was working together. Then it was a simple thing to adjust the butterfly on each carb to the same position as the other carbs. There was also a disabling pin used to raise the slide of one carb so that the jet-nut under the other carb could be used to adjust the mixture of that carb. This worked so well that I got almost 40 mpg on my 1962 TR-4, and the dyno said 80 RWHP! That was unheard of back in the day. Triumph TR-4's seldom got more than 70 RWHP.
Now I use a bank of vacuum gauges to do the same thing on my bikes, but there are no disabling pins that allow me to check the mixture, so that has be done by trial and error: Make a change in jetting, then road test. Keep it up long enough, and you will eventually find the sweet spot.
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Rider 123.
Reading back over your post, last one being Oct. I can only wonder why anyone would ride away with a new bike, find it stumbling and/ or misfiring and not immediately return to the dealer? Please don't misunderstand me, I am not trying to be critical here, just wondering why? As a fellow new (06) B12 owner, if I had detected anything but a perfect running bike, I would have gone back immediately. And after forking over a big lump of cash I'd make damn sure they would be footing the bill. It urked me when my 600 km checkup cost me $300. Secondly, my 06 B12 screw adjustment were factory set at 3.5 turns. Weren't yours? If not, then there may lie your problem. Still too lean.
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You said you don't want to mess with it right until the warranty is up.
But I'll second what Ray said... go ahead and drill out those plugs and give the A/F screws a 1/2 turn out. They are probably the most idle & off-idle related part of the carburetion... and they are set too lean from the factory.
Regardless... let us know the results of your TPS measurements.
Paul is correct. Your a/f screws really adjust fuel supply from idle to mid rpm range (where your needle jets kick in)
It is the 1st thing I would do. I bet a half turn out will cure your problem.
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When I needed to know how carburetor adjustments work I used this online guide which is simple and basic.
http://www.motorcyclecarbs.com/carbs101.pdf
The pilot jet is the part which supplies most of
the fuel at low throttle openings. It has a small hole in
it which restricts fuel flow though it. The pilot jet affects carburetion from idle to around 1/4 throttle.