Bandit Alley
MODEL SPECIFIC => SUZUKI BANDIT 250 & 400 => Topic started by: hangin_biposto on August 14, 2008, 06:27:30 PM
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... when I pull in the clutch. This is not a consistently occurring problem however it happens most often after longer rides at higher revs. The bike runs great otherwise; it fires up and idles well enough, has plenty of power, and it never seems to do it when shifting up - only when I'm downshifting to initiate slow turns or stops.
VW_NUT will probably chime in with the more technical tidbits as far as what we have done to the bike, but it's running the proper spark plugs, the coils/wires were swapped to see if that was the problem (used parts were installed) the rectifier was swapped just in case (again used) the carbs are synched nearly perfect, he's put the multimeter to it a bunch of times with no luck, we're pretty sure the jetting is decent (factory pro kit installed), good battery... blah blah... you name it.
He is getting very frustrated as he's not sure where else to look to eliminate this incredibly annoying problem, and it is unsettling to me because I am a new rider and have enough to worry about without having to get my bike running again mid corner.
Can anyone give us a laundry list of things to check to see if there's something we're missing? As I said, VW_NUT has been the one wrenching on it and he's now scratching his haid as to what should be checked.
*sigh*
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does it stumble/stall when hot, idling, and blipping the throttle? or is it *only* when you are downshifting your way to a stop?
you say randomly... you aren't able to to it reliably? it's not repeatable at whim?
Does it happen with other riders? or just you? (nothing personal, sometimes people cause things and don't realize it...)
I find my idle situation is a little flaky after a hot run. Sometimes it will idle high (like a lean surge), sometimes it will idle low, or fluctuate around. Usually a throttle blip and a few seconds of settling will put it all right. :shrug:
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I'm not familiar with the B4, but it likely has a clutch switch that needs to be released before the engine will turn over when starting.
It's possible that this switch is acting up, and occasionally cutting the power when you start to pull the clutch in. Maybe look at cleaning or replacing this switch. (Same goes for the sidestand switch, just in case it acting up under vibration.)
Just a thought...
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Check and adjust your clutch. I have a feeling it's dragging and causing the bike to stall at low revs... There are a few ways you can test. Pull the clutch and push the bike in gear it should have the same resistance as pushing in neutral. If it has more resistance then the clutch it dragging. You can also put the bike on the center stand, then pop it into first with the clutch held to see if the rear wheel turns freely.
Is ever difficult to find neutral when hot? it's a tell tale sign of a dragging clutch... or if the bike jumps forward when starting in gear or pulls forward in first if you don't apply the brakes at a light.
I hope this is what's causing you're problems because it's an easy fix. Cheers.
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I used to get this too. What i did was installed a hotter thermostat which seemed to help it. But this was after fitting new coils, reg/rec, cam chain and (used)cams. Have you got an inline fuel filter by any chance? Sometimes after some hard riding the float bowls can get emptied out etc.
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Ok, Problem only happens after riding the bike for a while. You have to ride for at least 20 minutes to get it to happen.
The bike has had the carbs cleaned and rebuilt and synched, hotter 195 t-stat, new plugs, idle is @1700, new battery, russel inline fuel filter, and new (used) gs 500 RR.
I first thought the idle might be too rich, but the plugs are very clean.
I don't believe its the clutch because the bike will idle just fine with the clutch in once it's running again.
Basically the bike stalls when you pull the clutch in to downshift at a light, or stop for the light. When you pull the clutch in it dies. I've found its happens a lot less if you let the revs come down natuarally and pull the clutch in at the last second. I won't always do it, but it doesn't usually do it cold unless its the first stop of the ride and thats just becasue the bike is still cold.
I really don't think it's carb related as the jetting feels very good. (I can post a pic of my plugs if that helps).
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Have you tried bypassing the clutch switch itself?
If you go into the bird's nest of the headlight bucket, you can just make the connection closed always by plugging the wires into one another. At least there you can see if it's the switch giving you problems.
If it's intermittant, I'd check the coil connections, the pickup on the starter side case and inspect all the wires for possible breaks. Could be that when things open up due to the heat, it shuts off the connections.
Weird though because theoretically, the bike would buck and bounce otherwise.
Maybe that's why I'm attracted to this bike so much, it reminds me of my VW with all the little quirks and niggles. (chest pains)
http://forum.svrider.com/showthread.php?t=81570
Something I came across in the SV forums.
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Yea it never hiccups other than when coming to a stop.
It does seem worse if you are just cruizing at a light throttle which is why it happens to hangin_biposto because she is a new ridier. Which is why I though it might be loading up, but like I said earlier the plugs are pretty clean.
This is very much like an old vw..... Good analogy...
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I have a bitch of a time finding neutral, but VW_NUT never had an issue so I think that may be operator error :banghead:
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how are the other clutch diagnostic? Do you need the brake when in gear with clutch pulled? With engine off, in gear clutch pulled, is it harder to push than when in neutral?
I wouldn't count out fuel. Maybe you're a little rich on the pilot jets or a/f screw. Is the problem better or worse when fully warmed up versus cold?
How about when you blip the throttle at idle? or rev it up to about 5 or 6 grand, let it run for a couple of seconds and then let the throttle snap shut, how does it behave?
A
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It's worse when fully warmed up. I am going to lean out the fuel screws and see if it stalls again. Thanks for all the info guys!
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I'm interested to hear how you make out. I'm having very similar symptoms with my ZX6R. It sounds like a combination of your problem and Andrew's. Every once in a great while after a long, steady run, it will stall when I pull in the clutch. Much more frequently I have a low or inconsistent idle that is is fixed by a quick blip. It's worse when warm. I've also developed a really cool backfire when I run WFO to 7500/8000 and then close the throttle. I leaned out the screws once and didn't notice a lot of difference. Maybe I'll go a little further. I can't believe a stock bike with a slip-on would be rich with out some other contributor, though.
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why lean out the mixture when popping? I thought popping was a symptom of being lean. Leaning the mixture would just make it worse? :shrug:
I'm prepared to be educated on that though.
I'm beginning to think that these issues can be a combination of lots of things (duh). See my other thread about pilot jets and lean surge for more of my symptoms...
Regardless of all that though, I'm of the opinion that this random stalling OP sees is a carb issue. Yeah, maybe the plugs aren't fouled, and maybe they look clean, but that doesn't mean there's not some little glitch in the carbs that's causing it.
That idle is a little high and might be masking other problems. You could be rich on the a/f screws but good on the pilot jet and just the difference in rider behavior is highlighting it for one and not the other.
Plus lots of riders do lots of little things, like lightly blip the throttle on decel without realizing it. VW_NUT could be doing all kinds of stuff that hides or compensates for the problem without realizing it. hangin_biposto, without years of developed habits just doesn't do these things and consequently finds all kinds of little problems.
I would recommend that you first get the idle set a little more sanely, down closer to 1-1,2 k revs, and then start playing with a/f mixture. If you're running that higher idle, you maybe aren't running as much on the a/f screw as you think you are.
Any other changes to the carbs that we don't know about? mains, needles, needle jets, float level etc.
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why lean out the mixture when popping? I thought popping was a symptom of being lean. Leaning the mixture would just make it worse? :shrug:
Because I don't think it's lean popping... it's an actual backfire. It's worse when warm, unlike lean popping. And leaning out the jets was more to help the occasional low idle/stalling.
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Leaned the fuel screws out a 1/4 turn, and took it for a ride. No stalls, however, when I pulled the clutch in a few times I got the stumble for a second that takes a few seconds to recover from. The idle dips to say 800 rpm for 2 or 3 seconds and then recovers to 1500. Not sure what causes it. Seems to happen most when cruising at light throttle between 4-7K, happens less when you are really hammering.
I can't lean it out any more because any more and it will bog out at low throttle. 0-1/8 throttle.
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OK, here's my .02$$ as far experience from car stuff is concerned with clarifying backfiring and raspberries out of the exhaust. I have owned cars that would throw fireballs out of the back in between shifts and sounded like a .45 when slowing in gear. All normal.
Backfire: this is when combustion comes physically out of the chamber and into and through the intake. Due mostly to mistiming, the event goes past the intake valves and into the airbox. This is way louder than decel popping and way more damaging. The intake valves were not designed to take this abuse because the heat can't be transferred from the face into the seat. That and they're built less robustly because they use fuel as well to cool them on the backside. In extreme cases, you can blow the carbs out of the boots or even the airbox. There are youtube videos of Mustangs that had a nitrous backfire blow apart a cast aluminum manifold on the dyno.
This is bad and something is wrong, no amount of dicking with your carb will fix this. Basically means something is out of time (physical timing or otherwise) and is only a matter of time till something lets go. Ever wonder why that screen exists in your airbox? Yep, it's a backfire screen to help keep your air filter from catching fire if this were to happen.
Raspberries; also know as decel popping: happens naturally under deceleration with closed or partially closed throttle, made even more obvious by an aftermarket can with a straight through baffle. The chambers of a stock muffler help hide this anomaly to an extent. Due to the mixture being sucked into the header pipes between cycles, the mixture then ignites in the pipes (naturally, because they're hot) and voila, popopopop. You can also get this on higher rev shifts between shifts as the mixture is moving so fast in and out of the motor that the interruption will mimic what happens in decel.
Made worse by bikes with PAIR valves that inject air into the exhaust to burn the excess fuel. This is actually not a bad thing and really a byproduct of the cam timing manufacturers use so that the overlap pulls in additional intake and excess exhaust in and out of the chambers.
I have no idea why this is always something that people try to tune out with fuel screws because in theory, it stands to add more fuel to the chamber to possibly make it worse. Ever watch a race when the guys are using maintainance throttle through a corner and you see flame and hear the popopop? That's what that is, a little decel popping on the overrun.
Here's the thing if you try to lean this out: you will raise combustion temperatures and perhaps even start to ping. Ideally, you should make sure the mixture is correct for the amount of air going in and out of the motor and not try to fight the byproduct of this, popping or otherwise, with messing with screws, etc.
Set up your bike so it runs well. If you don't like the popping etc that comes with higher performance stuff that was designed not to suppress this: go back to stock. You cannot tune around some of this stuff, it will only make matters worse.
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I don't mind the sound out the back at all, just trying to get rid of the stall. Flames would be good for tailgaters!! :beers:
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The only thing I can think of is something is up with the pilots; clogged or otherwise.
I know on my bike with 3.25 turns after a really hard run, the idle will dip just a little below where I set it and will come back up. Sometimes it needs a little nudge with the throttle but it hasn't stalled since the exhaust cam days. AFAIK stock setting is 1600 for idle so I set it right around there. I didn't want to risk too low also because of oil pressure (motor turning too slow). I spun rod bearings on the car with cams because the idle was set factory instead of higher.
I'd revert back to the box-stock Factory Pro suggestions and see if it does it even then. I think maybe being a full clip up on the needles may be what's doing it. I tried the fourth clip and I'm back to 3 and a washer (3.5) because it made the bike wicked-flat in that RPM range.
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on the middle clip it was really snatchy, now it is much smoother. It still stalled on the middle clip.
I think you may be on to something though cause I usually chop the throttle and overrunn the bike before pulling in the clutch. If I just pull it in randomly thats when the bike stumbles a bit.
If a light changes quick and I pull the clutch in and jam the brakes it will stuble just like you explan.
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Try a washer and the third clip, I think you may be a hair fat in the midrange. Not necessarily a bad thing but you could be possibly making more power a slight bit leaner.
Usually rich is very smooth and lean is very loud on the pipe with less go. Personal experience anyway.
Maybe you're used to the way your Duc is? No excuse though because the carbs should still work regardless.
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That was me with the backfires... sorry for the minor hijack. I need to pull my plugs and see what's what. I have a decent amount of sooting on the pipe.
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If you haven't done so yet, check the float height and condition of the float needles, as well as fuel line and petcock for adequate flow. Maybe you're not getting quite enough fuel into the bowls and/or the level is just a little low, causing too little fuel in the airflow once you let the revs drop as you pull in the clutch?
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Random thought for Tony - we were having the stalling issue before the fuel filter install right? I can't remember now... The damn thing has been tweaked so many times...
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yes. Fuel flow is not a problem..
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take notes. It's easy to think you'll be able to keep track of all the changes and the effects they have, but it's not (at least for me). :roll:
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I took the bike out last night to see if adjusting the screws made any kind of difference and though it didn't stall on me this time, the bike didn't feel as good as it did before. We took a slightly different route though, and I rolled one of the stops where it religiously stalls on me. The bike seemed lacking in power vs. before the screw adjustment.
One thing that Tony noticed is that my painted headers/pipe are a bit more white/chalky than they were before. The high temp paint was holding up quite well, as far as staying black, but it really lightened up the past couple of times out so he thinks things were running a bit hot/lean.
Apparently he tweaked it again after we agreed that it felt a little numb, as I got an email from him this morning stating that the bike was much happier today with 3 turns at the screws. I'm sure he will chime in at some point with the rest of the details...
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Yup much better. Almost got a ticket on the ride to work... I might try what Tomac GTI recomended and move the clip from position 4 to 3 1/2 (3+washer). I may check the pilot jets for crap & try to clean out the small ports into the intake. Maybe one of them has a little blockage.
Bike is still running strong and 98% of the time the idle is pretty solid. :annoy:
Plugs stil look good.
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Nice to hear you're closing in on it Tony.
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Ok, so I am honing on it a little further.
It seams like the bike is loading up a bit a low throttle say 1/4 or so. I moved the clip to the the middle position and it still felt decent, but still stalled on occasion. I moved it up again, and no stalling and the idle is rock solid when you pull the clutch in. No dip in the revs at all.
So here is the rub. With the clip on #2 some of the part throttle is pretty lean. At about 1/2 or so it's numb but does get a little better when the bike is warmer.
I called factory pro and they said to try #3 with a lower fuel height. I haven't tried that yet. I am wondering if worn emulsion tubes cause this. They look fine to me, but I don't know.
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Duane had a pretty interesting chart which showed throttle position versus circuits in the carb. Kind of helpful if you're getting that close to dialling it all in.
http://hondanighthawks.net/carb14.htm
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html
Between this and the FP site, you should get it sorted out.
If it's at quarter throttle, I'd guess more on the float level versus the needle but it's been awhile since I've seen the chart myself. I leave mine at/near stock when I set it up (14.6 IIRC) versus the 15mm that FP suggests. Thinking about it, means I'm leaner in that area versus their higher number. As Jay has attested this before, this affects your jetting across the range so if you do this, make sure everything is locked in and unchanged when you go to test it.
Also, Interfuse had a topic earlier that showed his emulsion tubes and extreme wear. I'd guage it on that. Obviously his look like a band saw had been through them but still. Wear is very apparant with city riding when the needle just saws in and out of the tube constantly versus completely in/out with closed and full throttle. Slide rattle doesn't help either.
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It doesn't take much wear of the emulsion tubes to start causing problems. Shine a flashlight down there and look at the step all the way around. Pretty much any deviation from perfectly circular is a problem.
.02
A
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Update,
Took a close look at the emultion tubes and they look ok.
Still stalled with the clip at position #2 and was very lean. So I don't think the clip is the problem. I checked the plug after hangin biposto rode it and it was darker than when I rode it. I am guessing I am rich on the pilot. I will try backing down the fuel screws again, or lowering the floats next.
I figured I was a little rich so why not try my "other" air box lid with holes in it to lean it out a little... Nope.... Way lean when I open the throttle. I guess I'll be putting on the stock one back on when I get home.
Thanks for all the info guys...
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Tony, here's what I experienced yesterday when my modified airbox developed a leak and caused everything to go wicked-lean in the pilot circuit.
I experienced everything you had until I chased the problem down to a failing seal and reset it all after going to all extremes on the screws. Too lean and the bike would stall, too fat and the bike would bog till on the needle...
-The main and the needle are the least sensitive to these changes (especially if you've already dialled them in according to FP). You'll notice that 1/4 throttle is what is the most affected (ironically the most often used throttle position).
Once you decide what setup to use on the intake and exhaust side of things is when you'll want to dial in the pilots. FP is right when they say to set your idle to spec and make sure the screws can hold it. The other circuits will follow pretty seamlessly. Make sure the bike is at operating temp when doing this.
-Once your screws are set and you're done, resynch everything. This affects how well the carbs react to throttle, closed or open. Also, changes to your idle screw will affect synch as well (at least what I've experienced).
I spent a couple of hours messing with this yesterday and endt up back at the settings that I had originally started out with. I'm happy I didn't get crazy and started going after the main and the needle because after I marked the grip and controls with throttle positions, it really helped me dial it all in and find the trouble spots. Using the combination of both those websites is a big help.
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What does your modified airbox look like? I have a bunch of holes in the back probably 8 7/8" holes I drilled with a uni-bit. I kept the snorkel.
I was thinking it wouldn't matter much as on my duc when it was stock ish I cut the whole lid of and it felt great. Not so on the bandit. Stock one is going back on as it ran much better down low with it & hangin_bipsto is not concerned with ringing the last 2 hp out of the bandit.
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hangin_bipsto is not concerned with ringing the last 2 hp out of the bandit.
not yet anyway... :evil2:
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It's basically a 2" PVC pipe flared on both ends like the factory snorkel. I alter the lengths to tune the airbox. You can actually hear where the resonance starts and feel where it affects the powerband of the bike. Kinda neat experiment.
Difference is the size is the same as the hole that the factory snorkel sits in (roughly 10% larger cross section) and you can alter the length to change the resonant frequency in the airbox. The rub here is that the entire box must be solid: no duct tape over holes since it affects the resonant frequency and also no leaks as its "unmetered" air. I recommend plumber's putty for resealing as it's easy to work with and relatively cheap.
To make it quick change I was insulating the snorkel from the airbox with weatherstripping as a seal. Since I was using a very cut up airbox, sometimes the seal would fail and basically make the carbs run very lean due to the additional air. I've since zero'd in on what I want so I made it more permanent by puttying in the snorkel now. I still have an unmolested stock airbox with snorkel just in case I need a control or want to go back to stock.
If you want to try it, I suggest using the stock length first and then shortening as you go along. The shorter the snorkel, the more up the RPMs move in frequency. You can use it as a tool to help fill in a dead spot in jetting or beef up a weak part of the curve.
Making it is quite easy as well as all you need is a Dremel, some heat and obviously the tubing. To create the bellmouth, you need to sand down the inside of the pipe into a taper about 1/2" in and use heat to flare out the tube. Try to mimic the factory flare and you should be all set. I use a screw through the top of the lid into a part of the snorkel for support in the back . I ground down the end of the screw flat so it's flush with the tubing.
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Update again... So I think I fixed it.
It turns out that I was indeed too rich on the fuel screws. 2.5 turns is the happy spot for this bike. Thanks for all the help guys! :beers: