Ran B400 out of fuel. Filled tank but now I wont start anc keeps backfiring

[novicoupe]

Ok I cant get my sons 92 B400 to start. It ran OK last fall as I had it at the shop to get it running after buying it. It was pretty cold out when I brought it home and could barely keep it running. Guy told me it was because of the temps outside but would run fine when warmer. Bike sat all winter but I did start it to put fuel stabilizer in it and my son started it once. Bike idled ok both times. Well I started it last week and it would barely idle did this for a bit and it ran out of fuel.  Filled tank today and now bike wont fire.  Seems like it wants to here and there but it is backfiring  some  as I am trying to get it going .  Anyone have any ides?? Weather is nice so so want to get this going so we can go riding..  Thx.

[greg737]

sounds like messed up idle jets to me. 

the idle jet fueling system is tiny and it is placed downstream from the throttle plates (closer to the engine), to allow it to take advantage of every bit of vacuum that the engine can generate at the relatively low RPMs you get while cranking (which, of course, is going to be much higher when the throttle plates are closed).  opening the throttle plates just dumps all the vacuum away.

the idle jets are very small items, located toward the engine side of the carbs.  a couple of months ago I disassembled a set of Bandit 400 carbs (BST32s) and when I took out the idle jets they were very crusty looking, and not just the needles but the tiny little emulsion tubes that go with them and the springs and the tiny rubber o-rings too.  and this was on a bike that would always start pretty well, but that's what you get on a 22 year old bike.

I know that nobody really wants to open up this can-o-worms but on a 22 year old bike a careful cleaning of this little fuel circuit could help.  although, once you have the carbs off the bike you might as well go through them completely, right?

I'm more familiar with Keihin carbs.  Mikunis seem to be a better product overall, for performance, but they have more intricate plumbing than the Keihins.  I guess that there's probably nothing better than a perfectly clean, well tuned set of Mikunis and nothing worse than a gummed-up, neglected set.

[novicoupe]

Thing is carbs were gone thru last fall. It would only start with full choke and giving it some throttle when 1st got bike. Took it to shop to get it running. Then rode it the 5 blocks home from shop lste last fall. Thats ride I was talking about in Op.  Then it sat all winter but wad started  cpl times abd ran at idle.

[greg737]

It would only start with full choke and giving it some throttle when 1st got bike.

well, that sure sounds like clogged idle jets.  when the idle jets are clogged you can get the bike started by making the choke fuel circuit do all the work, providing both the necessary base-level fueling plus the required cold startup fuel amount.  if you can get the engine to light and generate some RPMs then the engine vacuum goes way up and the main jets will kick in and add a little fueling.  this will give you a choke-sustained idle.

but you're saying that the carbs were fully serviced?  you're sure that the idle jets were disassembled and cleaned?

I have to ask... is the petcock "on"?  are the carb's float bowls full?  (not meaning to offend)

[novicoupe]

I will dbl check with bike shop but pretty sure they were.  No offense taken. Everyone misses the simple stuff sometimes.  Yes its on but I tried it several ways just to be sure.  Bike wont start at all now. Not even with full choke  or  any amount of throttle. Why would it be backfiring.

[greg737]

did anyone mess with the coils and high tension wires (plug wires)?  chronic backfiring sounds like an ignition timing problem. 

Of course, there are two types of backfires: one that occurs with an open intake valve, which results in an intake system backfire (I've seen some pretty spectacular intake backfires on sports cars) and the other is the one that occurs through an open exhaust valve.

it's a longshot but there is a way to end up with the ignition system wired completely backwards, which would cause backfiring.  just make sure that the coil for cylinders #1 and #4 is mounted on the left hand side of the bike and the coil for cylinders #2 and #3 is mounted on the right hand side of the bike.

unlikely, I know, but stranger things have happened.

[novicoupe]

No one messed with ign at all.  Plus as I've said bike was running  ok when I rode it home from shop last fall.  Just wouldnt idle without giving it throttle . But as I said guy said its because ofthe temps outside.

[greg737]

Bike sat all winter but I did start it to put fuel stabilizer in it and my son started it once.

Then I think it comes down to this... somehow. 

The variables in your equation are: time and the fuel stabilizer.  Guessing that these two variables have combined in some way to transform your recently cleaned carbs into gummed up, no longer clean carbs.

Well I started it last week and it would barely idle did this for a bit and it ran out of fuel.

Also, this sentence reads as a bit odd.  In the past I've tried to "idle" a motorcycle engine to empty out the fuel tank and carbs and it took forever.  I ended up giving up and just turned off the petcock and drained out the float bowls by way of the drain screws on the bottoms of the bowls.  Then I cranked it to (hopefully) suck out any gas in the carb's passages.  And drained the bike's fuel tank into the plastic container that I use to fuel up the lawnmower and string trimmer.

How long did you idle it before it quit?  If the engine did actually run out of gas (i.e. it emptied out the tank, fuel lines and float bowls) in a relatively short period of time I have to ask, how much gas was in it when you added the fuel stabilizer?  What sort of gas-to-stabilizer ratio did you make?

Have you gone down the carbs, opening up each float bowl drain screw for a few seconds to exchange whatever fuel is currently in them for fresh fuel from the tank?

once again, not trying to offend.  just attempting to narrow down the possible.

[novicoupe]

Ur not gonna offend me.    It had prob 3/4 tank when I added the stabil.  I know this is hard to believe on a bandit but I think the petcock has a small leak and most of the fiel leaked out over the winter.    Thats why it ran out fairly quickly. No I havent  done that to tryvabd get fresh fuel in the xarbs but I will. Ok this might he a dumb quedtion but will it get fresh fuel from the tank without a vacuum signal?

[greg737]

Ok this might he a dumb quedtion but will it get fresh fuel from the tank without a vacuum signal?

I looked in my Bandit 400 owner's manual and on page 54 the manual says that the petcock does have a prime postion.  Oddly, the position is shown as "PRI" on the owner's manual diagram but doesn't appear to be marked on the petcock's face.  Instead it seems that you (the owner) are meant to understand that moving the petcock's switch handle to point straight up puts it in the prime postion.

The owner's manual says that the petcock has 3 positions: when the petcock handle's arrow is pointing straight down it is in the "ON" position, when the petcock handle's arrow is pointing to the left it is in the "RES" position, and when the petcock handle's arrow it pointing straight up it is in the "PRI" position.

The owners manual also shows a small screw that sticks out of the petcock's face between the "RES" and "PRI" position.  It blocks accidental rotation of the petcock handle into the prime position.  This small screw has to be temporarily removed to allow the dial to be rotated all the way around to point to the straight up position which is shown as "PRI" in the owner's manual diagram, but isn't marked as such.

[greg737]

I know this is hard to believe on a bandit but I think the petcock has a small leak and most of the fuel leaked out over the winter.

That's not good.

From what I've seen with the Bandit, this leak that you have might not be the petcock itself.  It appears that on these Bandits the gasket between the petcock and the fuel tank is prone to failure with age.

So it might be the gasket and not your petcock that is leaking.  You might want to take a close look at it.

[novicoupe]

Thing is its not leaking currently.

[shidoran]

Does your oil smell like fuel?

[greg737]

Does your oil smell like fuel?

Good question.  Did the fuel end up in the crankcase?  I've heard of this happening.

[novicoupe]

Hey guys its been quite some time since I posted but wanted to give an update. Well  after a long battle (last one ever I might add) I got guy who worked  on bike before to finally work on it and get it running. Ign trigger went bad.   That and not sure if I believe him on thiscause I put stabilizer in tank and ran it for 5-10min.  But he said carbs were all gummed up again. Well anyway bike is running and son has been riding it as much as possible before winter.   It still has dome issues that need addressed with carbs but hes is nvr working on my bikes again.   Bike runs pretty well but idle is real touchy.   Sometimes it  idles fine, sometimes it  idles really,  really high. We have tried messing with it but as I said its really touchy.   Bike runs out pretty well and is a blast to ride.  Can throw it thru turns. I ride a 900rr and his bike is just  a lot of fun to jump on and ride . Its very nimble.     Other issue is it seems to be kinda flat down low. Maybe they are like that I dont know. Hope some of u experienced b400 riders will chime in. But once the revs come up wow.  But its not always like that.  U can be riding along about 50-60 mph and throttle it all the way and it just stays at 55-60mph and wont go any faster. Then all the sudden it might  take off and just climb,somrtomes it wont.  Its weird because I know bike has it in it . If u get on a straight stretch of rd.and  just go thru the gears and ride it like u stole it, it climb will to triple digits no prob.n