Bandit Alley
GENERAL MOTORCYCLE FORUMS => GENERAL MECHANICAL & TECHNICAL => Topic started by: OfTheSwamp on March 25, 2011, 02:51:22 AM
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Well, I think its a carb issue. Bit of background first: bought a 92 Bandit 400 a few months ago and almost immediately had problems with it. I took the carbs apart myself and cleaned them, and actually got it running again afterwards. However I kept having issues with both carburation and electrical things, mainly that the RR wasn't working properly and eventually killed the battery.
I finally caved and took it to a mechanic who sorted out the carb issues, and I had replaced the RR and battery in the meantime. Its been starting easily and running alright, except under certain circumstances. The mechanic replaced some of the carb o-rings and seals, and I'd already gotten the o-ring kit from another forum user, so they should all be fresh. The mechanic also replaced the sparkplugs, although they weren't in bad shape before.
It runs fine if I keep it at low revs and not at a constant RPM for too long, but if I take it onto the highway and keep it at higher revs for even a couple of minutes it dies as soon as I take it out of gear, and runs noticeably worse before I stop. I've almost had it strand me a couple of times, but if I let it sit for a couple of minutes, then give it full choke, it'll start right up again, and run normally as long as I keep it slow. I've also been able to keep it running as long as I don't let the engine drop to idle, making sure to constantly give it some throttle.
I've read as many related threads as I could already, and done a few simple things to check for obvious problems. I tried the carb cleaner-around-the-carbs-and-intakes trick to check for air leaks, but it seemed to have no effect. I also sprayed it directly past the intake box hole, and this killed the engine in just a couple of seconds.
What should be my next move? I meant to check the sparkplugs for discoloration as thats been a problem in the past, but darkness set in. Could the engine just be getting hot and causing an air leak that I can't detect at idle? Anyway, thanks for any help, I hope to be riding that thing every day as the weather turns nice.
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Is the replaced R/R working? When my r/r died, after coming off the highway I'd have to keep the revs above 3k or the bike would stall... Then eventually the battery would die.
Search the board the proper voltage readings for the r/r are posted somewhere.
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Also did you replace the battery? A failed voltage regulator can really mess them up.
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Hey OfftheSwamp
It can be hard to diagnose these things over a forum, so all you can do is to keep trying things and collect more data. Stick with it...
1. It sounds like it COULD be that the bike is running rich in the upper mid-range/top end, resulting in fouled plugs, which might indicate needle jet/main jet too rich. To check this, you need to look at the plugs, ideally doing a plug reading after a long, full throttle run. Dark, sooty, wet plugs would indicate too much fuel.
2. If the plugs look really wet, greasey, and collecting crud, you could have bad rings...resulting in oil migrating to the top end under extended full throttle runs, again fouling the plugs. A "leak down" or compression test would help you determine the condition of the top end. Doing a compression test "dry" and then again "wet" after squirting some oil around the edge of the pistons through the plug holes will help diagnose this.
3. Electrical issue can also be a potential cause, as the bike reacts differently once it is hot versus cold. There is a bunch of info on the forum about how to test for voltages, etc
Start with a good look at the plugs, and hopefully a compression or leak down test (if you have the equipment) and report back.
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Is the replaced R/R working? When my r/r died, after coming off the highway I'd have to keep the revs above 3k or the bike would stall... Then eventually the battery would die.
Search the board the proper voltage readings for the r/r are posted somewhere.
Also did you replace the battery? A failed voltage regulator can really mess them up.
I'm fairly certain that the RR and battery are working properly now, and I replaced them both at the same time. The old battery was toast after a few charge-drain cycles. With the new parts I haven't had any issues with it going undervoltage while running, or between rides.
After it dies on me, the battery is just fine, and the starter pulls hard still. Its gotten to the point that I keep a multimeter in my jacket so that I can stop and check it during rides if anything goes wrong.
It can be hard to diagnose these things over a forum, so all you can do is to keep trying things and collect more data. Stick with it..
Thanks for the encouragement and advice, I'll start with those things.
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I've had a bad idle that comes and goes and has been hard to diagnose. Two days ago it came back, would die at idle below ~2500 RPM but ran fine at higher RPM's. I had a rectifier/regulator I got of eBay for $20 so swapped it out. Now it idles fine ~800~1000 RPM. The rectifier/regulator that came on the bike was not original and was undersized.
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Alright, I'm back. Not long after my last post my bike got knocked over while it was parked outside my apartment and the clutch lever was broken off making it impossible to start or ride. I finally replaced it so I'm back in business.
After swapping the clutch lever back on I got it started up again, battery pulled fine although it took a few second to get it firing. Once I had it going it seemed to run fine. I took it on a short backroads ride to make sure there wasn't any hidden damage from the fall. Then I took it on a longer ride that involved a short section at ~8-9k RPM. Afterward it did the same old crap where it gradually idles down to dying whenever I'm not giving it throttle. I made it home fine (I have way too much practice at this) but it died the second I pulled up to my stop.
I started pulling the spark plugs out, unfortunately its difficult to get to the inside pair without removing the gastank, which is a huge hassle and I'm doing this all on the side of the road since I have no proper parking. One of the plugs was covered in soot everywhere except the spark surfaces, but was otherwise clean. The other had only a white coating.
I fired it up just fine after checking the plugs, it had no trouble idling. At this point I started poking around while it was running and noticed that two of the exhaust pipes coming out of the block weren't hot. At all. I could grab them fully without burning myself, and this was right after a ride. I then pulled the plugs on that side while the bike was running, and pulling either of them had no impact on the idle. I'm assuming that means that neither of these cylinders is firing at all? The other two exhaust pipes were hot enough to burn.
Their carbs had gas in them still, and its unlikely to be a coil problem since they aren't paired side to side. I'm about to call back that mechanic and ask WTF.
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Which pipes were hot? One coil fires 1 and 4 and the other coil fires 2 & 3.
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If the cylinders not firing are linked to one coil read this:
http://forums.banditalley.net/index.php?topic=8845.0
To fix the problem cut the wires back and crimp on new spade connectors.
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Hey Swamp
One of the plugs was covered in soot everywhere except the spark surfaces, but was otherwise clean. The other had only a white coating.
This comment is a little confusing to me... maybe to assist you, the following link gives you some examples of plug readings:
http://www.bobbittville.com/VW-PlugReading.jpg
(google "plug reading picture"s, and you will find lots of other examples)
Picture 1 gives an example of what a plug running rich looks like. Dark, usually dry, possibly loose carbon buildup on the insulator around the electrode. If this is what you mean, then this cylinder is running rich.
Picture 2 shows an example of what a cylinder burning oil looks like. A pretty extreme example, but usually a cylinder burning oil will have built up deposit, usually oily or greasy looking.
Your comment about a plug looking "white" is also confusing. Do you mean that the insulator is still a light white colour, or are you describing a plug that looks hot and glazed like picture #3 or #4? This could indicate a lean condition in this cylinder.
At this point, you may want to try a new set of plugs in all cylinders, and let us know what the plugs coming out of each cylinder look like. You may have to purchase a proper plug wrench so that you can replace all the plugs.
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Hey Swamp
One of the plugs was covered in soot everywhere except the spark surfaces, but was otherwise clean. The other had only a white coating.
This comment is a little confusing to me... maybe to assist you, the following link gives you some examples of plug readings:
Sorry I should have been more specific with that. I was actually looking at that diagram when I wrote the last post. The plug on the far right (when sitting on the bike) was similar to the "Carbon Deposits" picture, but with a very light black soot coating. It was not oily.
The far left plug was similar to the "Carbon Deposits" but with a white coating. I could also describe it as similar to the "Ash Deposits" picture but with only a slight coating. All of the plugs in it now have ~50 miles of use, so they're practically brand new as it is.
The cylinders that did not appear to be running were the two on the left side, while the right two appeared to be running. Like someone said the coils control 1-4 or 2-3, while I've got 1-2 working and 3-4 not.
I have a plug wrench and all, its just difficult if not impossible to access the tops of the plugs of 2 and 3 while the tank is on. I guess I could stop being lazy and just loosen it temporarily.
Tomorrow if the weather holds I'll get a more accurate diagnosis of the plug condition.
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Check the throttle linkage as well. The cable connects in the middle. One side of the connection goes to 1-2 the other side to 3-4. A problem in that linkage causing 1-2 throttles not to open could explain those two not giving power. Maybe.
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Update: Took it for another short ride after warming up. This time only cylinder #2 wasn't firing (counting left->right when sitting on bike) from startup, and never did start. I did the old spit test immediately after stopping the ride and it wasn't even a little bit hot.
Anyway I manned up and figured out how to access all 4 plugs without taking the tank off. 1,3 and 4 were all lightly carbon fouled, with a very light coating of dry soot. I ran it at low revs and idle for awhile after the high rev part of the ride, so this may only be indicative of idling conditions.
Plug 2 (the cylinder not running) looked like this: (http://img13.imageshack.us/img13/2716/sparkplug2001.jpg) (http://img13.imageshack.us/i/sparkplug2001.jpg/)
It doesn't appear to be in bad shape actually, but that cylinder isn't firing at all.
To do: -check that plug 2 is sparking
-Run it hard for awhile then stop and pull the plugs to assess their condition immediately afterwards.
All signs are pointing to it running rich at idle at least, but other than that I'm not sure. I'm hesitant to start messing with the carbs though since that's what got me into trouble in the first place.
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Hey Swamp
OK, yup...you need to get all cylinders firing first. Now that you know that 1 or more cylinder may not always be generating power, this is likely why you lose power later in the ride, because you are losing one or more cylinder.
So, a couple of things to check:
1. Spark? check the plug caps & leads making sure they are in good shape, and make sure the plug is sparking.
2. Fuel? Pull the drain plugs from the bottom of the carbs, and make sure they all have fuel.
I wouldn't get too worried about more plug readings until you have all cylinders actually running.
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1. Plugs and caps are in good shape. Pulled the questionable one and sparked it against block to be sure, seems to spark fine.
2. All of the float bowls have fuel. I drained gas enough from the questionable one to be sure.
I also checked to ensure that the air filter and intake weren't clogged, and they were free of obstructions.
I played around with the pilot screw settings, and for some reason they were set to over 5 turns out. This was the first time I've touched them since getting it back from the mechanic, but I remember having them at no more than 2.25 turns out before I took it to him. It also seems to be way outside whats recommended the max is for a given screw size.
What's next on the checklist? I was thinking about getting a compression tester anyway, that might be a simple next step.
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So wait, I'm still back on one of your earlier posts.
You said you pulled the plugs from Cyls 2 and 3 and it had no effect on the idle? As in they were out of the cylinder head?
If that's the case your problem is an internal engine one. As in top end is screwed up.
Otherwise I'm going with that cylinder isn't getting fuel. Did that plug smell like gas when you pulled it out?
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So wait, I'm still back on one of your earlier posts.
You said you pulled the plugs from Cyls 2 and 3 and it had no effect on the idle? As in they were out of the cylinder head?
If that's the case your problem is an internal engine one. As in top end is screwed up.
Otherwise I'm going with that cylinder isn't getting fuel. Did that plug smell like gas when you pulled it out?
Sorry I should have explained that better.
When I "pulled" them, I just plug the plug cap off to deny it spark, I didn't remove the plugs from the head. Since I was pretty sure that cylinders 1 & 2 (not 2 & 3) weren't working anyway, I yanked their caps one at a time to see if it impacted idle. Since neither of them did, it just adds to my evidence that they weren't firing at all.
[As an aside, I did run it briefly with the #2 spark plug pulled out (when I was checking to see if it sparked), and the engine actually ran better with the plug completely out of the block. This makes me think that its still holding compression, and with the plug removed there wasn't the resistance from that cylinder holding it back]
Since then I've realized that #1 is firing sometimes, but not others. I can't pinpoint what causes it to start or stop firing. I'm also shocked that the engine will even run when only two cylinders are firing.
Now that you mention it, the spark plug in #2 wasn't even wet with gas when I pulled it out on several occasions, so you're probably right that its not getting fuel. I'm pretty sure at this point I'm going to have to pull the carbs out and see what the hell is going on, but I'm not looking forward to it. I'm first going to call up the mechanic and ask him what he did a couple of months ago.
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Honestly pulling the carbs on these bikes isn't bad. And once you have them off, check your float level and the needle to make sure nothing is clogged up. It sounds to me like the fuel is in the bowl but isn't enough to be sucked up in the jets when you open it up.
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Honestly pulling the carbs on these bikes isn't bad. And once you have them off, check your float level and the needle to make sure nothing is clogged up. It sounds to me like the fuel is in the bowl but isn't enough to be sucked up in the jets when you open it up.
I know its not that bad, I've done it several times before but its just a huge pain to get it apart and back together. I hope its as simple as the float level being off. That was also most of the point of taking it to a mechanic was to get all those little details set right so I didn't have to mess with it.
The biggest problem with working on it is that I don't have a good workspace. I don't have a garage or even covered parking to work it, let alone a driveway. I would pull the carb out and drag it inside my place, but the apartment would reek of gas for a week and my roommate would kill me. I'll probably arrange to use a friends garage nearby and hope I can figure it out in an afternoon and ride it home.
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I've been having the same problem lately.
Bike broke down , luckly only about 5 mile from home, but took me an hour to get back, in short bursts.
get it running ( all spluttery and having to keep revs high , ) get a short way up the road for itto die again ,and then not start for 5 min.
Did a splash test and #1 did not sizzle,
I changed the plugs and it seamed to be running ok again.
I did test all 4 for spark , as it seamed like it wasn't running on at least 2, maybe more when i last rode it ? .
Did the splash test on the down pipes and all 4 sizzled, got the bike out me back gate and forgot to put it in neutral first befor putting the stand down, so it cut out .shut the gate, started it back up, and now #1 is not sizzling again.
Thing is it sounds like its running fine, revs up and all .
Gonna check the carbs yet again ( had probs with them when i first got the bike .)
Cant take it for a test ride after yet though, as me left fork seal is shot , leaking oil all over the place, which has killed the brake pads on that side :(.
Friggin bike is driving me crazy.
First bike in 20 years, and its spent more time sat in garden in bits than under me,No money to fix it and im now missing the little amount of sun we get here in the uk .
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I know this sounds weird but I had an old GS650 that had a coil go bad. WHen the bike was colder it was fine but as soon as the engine heated up enough to get the coil hot it lost spark. When the bike goes tits up do you get spark on all cylinders? My suggestion is wait for a day which is super nice drive the bike around your house until it dies. Then check every cylinder for spark. If all spark fine, great you just eliminated that type of problem and can concentrate on fuel/air. For fun I would also check to see if your breather hose to your fuel tank is not clogged. When the bike dies next try opening the fuel cap. IF you hear a whoosh or a pop than what is happening is that there is not enough air to displace the lost gas in the tank and vacuum is starving the bike of fuel. You could also run around with the gas tank cap open a bit to see if that goes away. Also that plug you pulled looks pretty rich to me or is not getting a strong enough spark.
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Sorry to resurrect my thread, but I've finally had time and good weather to work on the Bandit. I also lost a little motivation to work on it because I bought a '98 Bandit 600 back in April and have been having a blast with it.
Anyway, I'm basically back to where I was in my last post from the previous page. In the last few days I have:
- Recharged the battery, it was a little low from sitting too long.
- With no gas in the tank, I sprayed some carb cleaner around the air intake and it fired right up. It only ran for a few seconds so I wasn't able to determine which cylinders were/weren't running.
- Replaced all of the spark plugs with brand new ones I had from awhile back.
- Drained as much gas as I could from the carbs and gastank, then added fresh gas.
- Removed the carbs yet again, check for obvious blockages and then put them back in place.
- With bike fully assembled, gastank restocked, battery charged, and ensuring gas in the carbs, I got it to fire up pretty easily. At most it was only running on 3 cylinders (1,2,3), and dropped to just 2 (2,3) after idling poorly for a minute or so. After that it would not stay running for more than a few seconds and was still only firing cylinders 2 and 3.
To do:
- Find adapter for compression tester, I didn't research thoroughly and mine doesn't fit in the plug holes.
- Find better way to determine if the plugs are sparking. I can pull them out and watch, but I'm never sure whether they're going or not.
Questions for y'all:
- I've got the pilot screws set to that ridiculous 5 turns out the previous mechanic left them at, is there a way to determine a more optimal setting?
- Same goes for the idle adjustment screw, I left it set to basically zero throttle opening.
- How accurate are the resistance tests on the ignition coils? Both of them are well within spec.
- How long would it take with the bike running for a spark plug to get fouled if it were receiving gas but not firing? I only had the bike running for a minute, maybe 2 cumulatively, but when I checked the #4 cylinder, its plug was clean as a whistle. The carb attached to it had gas in it.
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You can verify the plug is getting the voltage to spark with an inductive type timing light. Just put the pickup over the plug wire in question (when running) and if the timing light will strobe when the trigger is pulled, that plug is getting power.
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This sounds like a ridiculous question, but it happened to me so I'll ask. Did you check to make sure that the connectors at the coils are good? I put my 400 away for the winter and when I went to get it running in May (with SeaFoam in the gas and a fresh oil change) it was running worse then I've ever seen it, and since I basically rebuilt the bike at this point that's saying something. I resynched the carbs, replaced plugs, checked over the whole bike and basically couldn't find the problem. My dad happened to reach around the tank while we were synching and bump on of the connectors on the left side coil and all of a sudden she ran great. I checked and the connectors were all gunked up. Some sandpaper and some contact cleaner as well as some dielectric grease cleared up the problem, and aside from a couple hicks (I'm pretty sure one of the PO's damaged the top end a bit, and just don't have the money or time right now to take down the top end and check it out) the bike runs like a top. Got rid of a hesitation around 6k as well. Just a basic thought that I'd overlooked. Worth checking.