Bandit 400 Carb Issue - Help Please!

[KevTM]

Got the bike taxed today and went a wee run. The first 20 mile were ok then it started running on what sounded like 2 cylinders. I thought ok, I'll get new plugs (since i had already replaced two and knew two were a bit so-so).. changed them and it was still the same. Pulled the tank off, plugs out, noticed they were dry so knew fuel wasn't getting through. Took the airbox off and put my hand over each carb and hit the starter.. pulling the fuel up ok on all carbs.

My question is, why aren't the carbs pulling the fuel up?

Bike is running again but begins to stutter above 5k, if under load and i try to give it some it'll just bog down above 5k.

I'm going to pull the carbs apart again and give them an overnight soak in after i've cleaned them just to be sure. Any preference in what to soak them in? And any ideas as to why fuel isn't getting pulled up.

[BanditsHigh]

Which two cylinders ... could be one of your HT coils is beginning to give up

[KevTM]

Checked the coils as per haynes manual, resistances on primary and secondary side seem ok (might be a different story under load though)..

I don't think it's the coils though as the plugs were bone dry, definitely wasn't getting fuel.. sa soon as i 'primed' the carbs again it started on the button.

oh, and the bike eventually didnt run at all, just started running on two, then down to nothing.

[b-f-c]

I had one of these before.

If its anything like mine was, the tank is very slowly rusting from inside, and the rust is so fine it was making its way into the carbs and choking them up.

A clean out of the carbs, a fuel filter and the possibly a tank treatment might be called for.

[KevTM]

yeah my old tank was rusted. I got a new one, rust freee, cleaned it out, new fuel lines and filter.. carbs have just been cleaned out but they were manky inside! might need another clean.. it's all i can think of.

The needles in the carbs are straight, the tips of them are like new, i couldn't see any faults.. they slide fine.

[b-f-c]

Its because they're a grey import. I've never had it on any other bike. The rust is a fine as talc. Air gun through the the lot. Tank, pipes and carbs.

I'd done this half a dozen times before I thought of using a fuel filter

Something like POR 15 through the tank will help prevent it re-occuring (remove the fuel tap 1st though)

[KevTM]

aye they are supposed to be quite bad for it rusting. Mine was sitting outside for almost 2 years that's why the original tank was rusted. The new tank however is clean as a nut! and it's all been cleaned out, new fuel lines.. I doubt it's rust but yeah, it probably is crapped up with something..

I just bought some carb cleaner so i'm going to strip them again (argh).. crappy job but someones got to do it.

Just wish i knew more about carbs.. bit too late to learn though are they're all friggin FI nowadays,

[b-f-c]

Good luck sorting it

Honestly, it will look shiny and clean, but underneath the shine the bugger is slowly rusting. The mechainc I spoke to at the time said the slight silver/yellow colour I could see in the tank was the rust, there was no other sign.

It was one of the reasons I got rid of mine in the end

[KevTM]

Stripped the carbs right down (exlcuding seperating them etc obviously), took the jets out, needles, split the floats and checked the needle in them.. carb cleaner, air compressor, should be clean as a whistle.

went out on it, pretty much exaclty the same, starts hesitating at 6k..

could it be anything to do with valve adjustments or anything like that?

[KevTM]

you can rev it past 6k in neutral (no load) but it's rough and will struggle to get to 9k - 10k, occassionally one or two small backfires and a little black smoke.. If i try give it full throttle it'll bog down, got to give it part throttle to get the revs to rise.

[Blau Zedong]

Mine was an absolute cvnt for this, it would usually result in it fouling the plugs. Never really solved it untill I had the carbs ultrasonically cleaned, apparently the main problem was a blocked pilot circuit.
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[KevTM]

Stripped the down again today, bathed the bodies in carb cleaner (got a 5 litre bottle today) scrubbed everything with a toothbrush etc.. all the usual, compressed air, carb cleaner spray. Nothing is blocked!.. Still the same result though, perhaps mildly better but not by much. Checked the float bowl heights and jet sizes as per manual and all are ok.

I'll pull the plugs tomorrow morning, was going to do it tonight but i forgot and put the tank back on .

I'm assuming spark gaps wouldn't be out that much out of the box, I haven't checked them yet, I'll do that tomorrow, too.

Failing that i'll try the coils off the other bandit first just in case like Bandtshigh says, they are on their way out.

[KevTM]

Got the bandit running fairly well.. it's a bit boggy around town/low revs but no to the extent it stalls.. all good all the way up to bout 10k then you can hear it maybe burbling a bit. Going to have to find a new endcan for it and see if that makes a difference.

[baldy]

Have you balanced the carbs? It can cause very strange problems if they aren't balanced.
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[KevTM]

yup, balanced them again today after fixing the prob.

regarding the poor running at idle, and needing a few revs or a dip of the clutch to get it going from a standstill I think i'll fine tune the pilot screws tomorrow.. then it's on to valve adjustments. It still has some hesitation above 8-9k in the higher gears too.. fun eh?

[KevTM]

Took the carbs off this morning. I checked/adjusted the float heights again. The pilot screws were 2 turns out on each carb, I think the base setting is 1.5 turns?

After sticking the carbs back on I balanced them. I set the pilot screws at 1.5 turns out and tried to fine tune them but it wasn't too 'clear' so I set them all about 1.75 turns out (somewhere in between)

Went a run and I don't think it's as bad around town, although I haven't gone a long enough run to find out. It runs great between 3k - 8k. As it gets to 8k there's a hesitation and that sort of goes up through the rest of the rev range (it's ok in 1st & 2nd gear, 3rd on and it hesitates)

Any carb gurus got any ideas? I've been reading up on carbs and what affects what, float height, pilot screw, needle jet, jet needle, main jet etc etc..

What would cause the hesitation from 8k on (this is at 3/4 - full throttle), going from a lean or good mixture to a rich mixture or vice versa?

[Mad_Sunday]

Does it still have the original HT leads? If so take them off and throw them as far as you can. Replace them with nice new stuff and try again.

Just bought a 250 Bandit for my missus so expect to have loads of problems getting it running 100% for her.

Pete
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[KevTM]

It's ok, got her running sweet today, sounding much healthier and revving all the way to 12k (never tried any further) in 6th! Idling fine and great around town now! Great on and off the throttle at all positions (full-1/2, 0-full, 3/4-1/2, 1/8-full etc etc lol)



I take it you can just take the HT lead out from the coils? just unscrew like you do on the plug caps? Was going to but a length of lead today and do that but I wasn't sure whether they come away from the coils ok or not. Might just replace them for the sake of it anyway.

Good luck getting the 250 running nice.. quite rare those ones eh? still quite nippy from what I hear.

[Mad_Sunday]

They are probably "fixed" into the coils, I just rip them out and then glue new ones in. Don't worry about being able to connect them to the internal wires, a spark will jump 6mm if it needs to. Just get the copper as near as possible (both the same distance) and you should be OK.

The 250 looks wicked, it's a sort of apple green which looked kind of weird. I thought it was a strange colour for someone to choose for a re-paint, then discovered its the original colour! It has grown on us!

I'll get a photo of it on here soon.

Pete
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[chillyman0]

yeah will be intersting to see the 250 too

got some bad problems with one cyclinder on my bandit 4 really dont know if its carb or cyclinder problems.... fancy coming all the way down south here to have a look at it for me KeV6??

got some updated pics in my thread btw

[KevTM]

I've had enough tinkering with these bikes lol.. other one decided to run on 3 just before it went for its mot, just cleaned up the plug (slightly fouled with being idling etc and not been a run)

What are your plugs like anyway? Might tell you a lot about what's happening.

[baldy]

[Mad_Sunday]

You muppet, what do you think about the gap at the plug? There used to be a "device" called a spark booster, all it did was put a gap in the HT lead. HT btw means high tension, that's about 30,000 volts. I've done this many times in the past so I speak from experience. You I suspect don't. If the leads are old they will "leak" that 30 thousand volts before it gets to the plugs so they need to be dumped.

Pete

p.s. electricity travels at the speed of light, 186,000 miles a second, it is not a variable! So fix your own bike.
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[Mad_Sunday]

Here's a picture of the 250. Taxed it today and went for a blast. Revs right round to 16,000 ok but got issues just above tickover. Any of you guys got spare parts for 250/400's I need to find a few bits for it.

https://madsunday.fileave.com/cathybike.jpg






Pete (& Cathy)
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[Pete.]