Another 400 carb issue

[OfTheSwamp]

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.

[interfuse]

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.

[interfuse]

Also did you replace the battery? A failed voltage regulator can really mess them up.

[pmackie]

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.

[OfTheSwamp]

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.

[canyonbreeze]

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. 

[OfTheSwamp]

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.

[interfuse]

Which pipes were hot? One coil fires 1 and 4 and the other coil fires 2 & 3.

[interfuse]

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.

[pmackie]

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.

[OfTheSwamp]

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.

[canyonbreeze]

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.

[OfTheSwamp]

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: 

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.

[pmackie]

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.

[OfTheSwamp]

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.