Bandit 1200 bogging down & dying

[Tierbirdy]

Ive got some odd problems with my 2001 Bandit 1200S with about 24k on the clock, that have me scratching my head.

I've only owned it for about 2 weeks now which is bloody annoying. And its started to bog down really badly for bizarre reasons. This is a bit long winded but bear with me!

I've already noticed its a very cold blooded bike, Im assuming being a big 1200 lump it takes a while to get up to operating temp and it just doesnt like being run too hard when its cold. So thats not really a problem, I normally start it up with full choke, and leave it to idle for a minute or so whilst I faff about putting gloves, helmet etc. on. Ride away and its mostly fine, a little bit boggy perhaps at low revs but I put that down to the engine being cold, by the time I get to the end of the road its normally fine.

When I test rode the bike it was absolutely flawless, didnt skip a beat. No bogging whatsoever, started from cold (made sure to feel the engine casing, it was stone cold), not a problem.

Rode it home about 60 miles of motorway, not a problem the whole way. Once I got it home I realised the bike also has a petrol tap that I hadnt noticed, and it had been left in the prime position, so I turned it to on and thought no more of it.

The next day, it starts running a bit boggy and crap, I put this down to being low on fuel (it had gotten to about 2 bars of fuel left at the point), so I topped it up and threw a bottle of redex in there for good measure. Hey presto this cured the problem and away we go.

For the next few days, not a problem.

Then coming home from work a few days later I get caught out in a absolute fekking monsoon, and the bike starts running like absolute crap, bogging awfully, will barely go above 30mph, stuttering, juddering, feels like its going to stall out at any moment. I limp it home, kick the tyres and go inside to sulk and worry about it the next day when the weather isnt crap.

The next day, it runs absolutely perfectly. Nice sunny dry day, doesnt skip a beat.

It runs ok on and off for the next few days, some minor bogging that resolves once the engine has heated up. No major dramas.

Today on the way to work, its absolutely pissing it down, and the bike runs like crap the whole way there... now its bogging to the point where it actually does stall. When you have to stop at roundabouts/red lights etc it idles at about 1200RPM... which over about 5-10 seconds slowly drops to 1000... 800... 600... stall. So I have to sit at the lights blipping the throttle like a chavvy little scrote on a ped to stop it from stalling.

On the way home from work it gets even worse... to the point where it died completely. Rolling on the throttle youd accelerate normally for a couple of seconds, then it would bog down... and the more throttle you give it, the less power you get, to the point where the engine cuts out, and wont start again.

HOWEVER at the back of my mind, I vaguely remember when I was first looking this problem up, I read somewhere about putting the fuel tap to prime and see if that solves the problem... so I give it a go, and bam it starts first time and rides the rest of the way home perfectly. Im running low on fuel again as well, so I stop and fill it up. Out of curiosity seeing as the last time I filled it up, it stopped bogging, I put the fuel tap back to the on position, and it rode the rest of the way home fine.

So, whats got me confused is I cant figure out what the relation is between these problems and where the route cause may lie.

So things that make the problem worse:

- low fuel
- rain

Things that make it better:

- running it on PRIME
- topping up the fuel

Now, the low fuel and needing to be put on prime makes me think perhaps theres a vacuum issue. But I dont know how to diagnose this or what could be causing it. But for the life of me I cant figure out why the rain sets it off or makes it so much worse?

I've had a look on various Bandit forums (which I cant post on because one you have to pay £20 membership to join and frankly fuck that, and the other is manual admin account activation which Im still waiting on) and the main culprit seems to be the air filter being clogged, or the carbs needing new needles/floats/someone has been dicking about with the jetting. But none of these explain why it becomes a problem in the rain? Does anyone have any ideas or suggestions?

To the best of my knowledge the bike carbs are stock and hasnt been rejetted. However the previous owner has put a Micron exhaust on it. Ive not had a chance to inspect the air filter yet, but the Bandit forums seem to say that anything other than the OEM Suzuki filter makes it run like crap, as the Bandit apparently runs lean, so high flow/K&N filters make it even leaner and bogs/stalls.

[chris-red]

Fuel Tap is knackered by the sounds of it. If it is a vacuum tap there should be a line from the tap to the engine/carb somewhere (obviously it isn't the fuel line.) It'll be the thin one if you are in doubt.

Make sure it is attached at both ends and seals well. You may want to take it off completely and blow down it to check it. If it is split/blocked replace it. Any motorfactors should do airline/washer fluid line that will work for pence.

If that is fine then I'd get a rebuild kit and rebuild the fuel tap it is normally pretty straightforward to do. Plus at £10.75 it doesn't exactly cost much.

IN the mean time you shouldn't have any issue just running it on prime all the time. My GS500 was like that I just lived with it.

The water issue sounds like it could be something else, probably electrical or it could be a phantom issue related to the fuel tap. Fix the tap first then see how it is.
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[Tierbirdy]

Well Ive ordered that and will give it a go, and a service too. Hopefully new tap, plugs & filters all round will help.

[bamt]

For the rain problem, have a look at the front of the engine. Just above each exhaust port there is a drain hole to allow water water to come out of the spark plug recess. If that is blocked and the seal at the top of that recess around the plug lead is damaged or missing, it could be filling with water and causing spark issues.

Worth checking as it costs nothing to fix.

[Tierbirdy]

Brilliant, wasnt aware of that and thats a nice easy check/fix as well!

[Matt B]

[mudcow007]

Could it be the mixtures have been messed about with?

Im only saying this as when i got my 600 its was a mess, hard to start etc, even after replacing normal service stuff

found it was the mixtures had been messed about with, reset back to normal an it starts like a champ, full choke then drop it to a quarter for a mile or so then good to go.

In the winter its maybe a mile & half

Oh an can confirm my plugs get soaked. the drains by the headers seem clear, but when it rains I always get water in 1 - 4 cylinder recesses. I have seen peeps putting silicone all over the plug caps dunno if that helps though?

[Kris]

As already said, fuel tap probably needs a rebuild.

I had similar on mine.
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[kingmunky]

If you're cleaning out the fuel pump, remember to clean out the high pressure filter, tucked away in the white plastic casing, after the pump motor. This always gets clogged up; get the carb cleaner sprayed all over it then a few passes with compressed air until all the crap is blown out.
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“I'm not good at many things in life but I am a fair hand at drinking tea.”
Current bike: 2011 Suzuki DL650
Previous bikes: 2008 Bandit 650, 2000 XJ 600 and 1998 GPZ500

[Tierbirdy]

[chris-red]

[Tierbirdy]

Serviced it today, new oil & filter, spark plugs, air filter, and did the fuel tap rebuild kit whilst I was at it. Easier than I thought it would be.

First things I noticed: the old air filter was a K&N, however it was absolutely caked with black gunk. So I figure air starvation was definitely a contributing factor here. Thats now been replaced with a Hiflo Filtro "OEM" air filter. The spark plugs were pretty nastily corroded due to being sat in water I assume, the business end of the plugs seemed alright, no abnormal discoloration. So perhaps theres some electrical conduction/spark issues due to corrosion too.

Put it all back together and it seems to be running alright, doesnt seem to need as much choke to start now either.

Took it for a short test run, 10 mins or urban riding as I dont have time for a long distance motorway run or anything at the moment. Seems to be running much happier. No noticeable bogging upon start up and pulling away, even with a relatively cold engine. No hesitation on accelerating hard. And I can happily trundle along stuck heind a learner driver at 10mph in 2nd gear without it juddering and feeling like its about to stall out.

I'm cautiously optimistic to say its fixed... but I need a proper long run to check, and also I actually need it to rain to see if that issue is still playing up! Who'd have thought we'd be WANTING for rain in England?

[Tierbirdy]

Bumping this back up with a 2 weeks later report.

Its still not rained so I still cant say for certain thats fixed. The bogging down seems to have gone though. Even when running low on fuel its not doing it anymore, so yay for that.

But that brings me onto my next/new problem: the MPG has gone to shit.

Ive filled it up twice over the past two weeks, each time getting about 100-ish miles before switching to reserve. Topped it up today, put 16 litres to brim the tank and that had gotten me 105 miles, which according to my MPG calculator gives me about 32MPG. Prior to servicing and renewing the fuel tap, it was closer to 45-50MPG.

What have I done wrong? One thing I noticed at the time thats been pointed out to me, when I put the repaired fuel tap back on the bike and turned the tank the right way up, fuel leaked from the fuel tap with the tap in the ON position. I thought nothing of this at the time as I assumed "well its on, so fuel should be coming out right?"

I cant figure out what could have gone wrong in re-assembling the fuel tap as its only got 2 moving parts and it only fits together one way. From what I can tell its a vacuum driven carb not gravity fed so it apparently shouldnt be leaking any fuel? Am I getting shit MPG because its constantly running fuel even when it doesnt need to be?

[Hawkeye1250FA]

I would have suggested it's in "prime" position rather than "on" but you've checked that....?...

This old thread might be worth a read.

https://www.bikechatforums.com/viewtopic.php?p=1977369
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1993 RF400R - 2002 Bandit 1200 - 2012 1250 FA

[Hawkeye1250FA]

I should add congrats as well on potentially solving the problem! 👍
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1993 RF400R - 2002 Bandit 1200 - 2012 1250 FA

[Tierbirdy]

99% sure it was in the on position. Going to take it off again and double check Ive not done something daft like put the diaphragm on the wrong way round or something. Though Im sure that would be impossible to do it seems a logical place to start - fucked about with the fuel tap and now Im getting shit fuel economy.

Im not 100% certain on how a vacuum fuel tap works... from what I gather, if everything is assembled correctly it should be air tight and no fuel should be flowing, unless the carbs are sucking on it to open the diaphragm and let the fuel flow? So if fuel is flowing when the tank is off the bike and tap in the on/reserve positions, then something wrong with the diaphragm/valve/something?

Jesus christ Im buying a modern fuel injected bike next time... carbs and vacuums are black magic and witchcraft

[Tierbirdy]

Ok so bumping this back up again, to confirm that the problem is indeed NOT fixed.

Last night against my better judgement, I gave a mate a lift in a torrential monsoon (because of course he picked the ONE day of the month it was raining like that scene from Forest Gump to go do something), and I spent 3 hours at the side of the M23 looking like a drowned rat waiting for the AA.

Riding it through town was no problem, it was fine for the first 10 miles or so, then I got onto the motorway, fine for the first few miles as well. Then every now and again youd get a little judder as it felt like it skipped a beat.

Then a few miles later it felt like it was lacking power, it wouldnt go above 80mph/5k in 5th gear, so I figure perhaps its bogging a little in the mid range, so kick it down to 4th to try and power through it... big mistake, it now wont go above 70/5k in 4th, same with 3rd... eventually Im stuck struggling along at 40mph limping to the next slip road, as soon as I get to the slip road and clutch in to stop at the red light, the bike totally dies.

Unlike last time where I could get it started again by running it on prime, this time its dead dead. It turns over, it might come to life for half a second then it cuts out and dies, popping and backfiring.

So its getting fuel, but theres something electrical going on that means its not getting spark, or not enough spark to keep it running.

The spark plugs are brand new, changed them myself a fortnight ago. So where to look next? I dont see anything obviously wrong with the HT leads etc. Are there any obvious electrical weak points I should be looking for?

[chris-red]

My advice below is generic, however with these sorts of issues people with model specific advice would be more useful, this may be a common thing. I.e. I know the TDM I ride has a couple of model specific issue for poor wet running.

Water is getting in somewhere. I'd start by examining the ignition system i.e. Coils, plugs, leads.

Do the plug holes have water in?
Is a drain blocked?

With my TDM900 I had an issue where the Spark was arcing to the frame through the lead in damp conditions. To fix I replaced the lead with high quality one and wrapped them in plastic insulation (designed for HT leads). The TDM also has an issue where the coils can get damp and screw with the running. I waterproofed them best I could and it had been fine since. In fact it has been running on pattern TDM850 coils that I waterproofed for twice as long as it had the OEM ones for.
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[Tierbirdy]

Spark plug holes were bone dry, drains dont appear to be blocked. From what I can tell theres no water sitting ontop the plugs. Plugs are brand new, changed them about 2 weeks ago.

Someone else reckons the coils are a weak spot on the Bandits, said he had a similar problem with a Bandit 600, not sure how to check these, but visually they look fine, theres no signs of corrosion on the contacts or anything.

Arcing from the HT leads isnt something I'd considered, Ill have them out and give them a good looking over.

I did notice the fuel line from tank to carb was slightly perished and had 2 small splits about 5mm infront of the fuel tap, so for now I've snipped the damaged section off and made the hose about 1cm shorter. Will replace the whole hose eventually but it looks like a ballache of a job to do. Part of the frame sits right above where it plugs into the carbs, so looks like you have to take the carbs out to connect it

[chris-red]

[Tierbirdy]

For a bit of closure, and possibly help to anyone else who has a similar problem. I think this time I've fixed it for realsies.

https://i.imgur.com/1cXJpVf.png

I was missing these things!

A mate of mine who had a Bandit 600 with an identical problem said to look for them, as its a common thing to go missing when people change spark plugs etc.

Seems the previous owner had changed the OEM right angle style spark plug caps to NGK straight "racing" leads/caps and forgot to put the plug covers back on... Having never owned a Bandit before I had no idea these things even existed let alone were missing.

Bought replacements, fitted them, riding in the rain no problem now. Will probably get round to replacing the NGK leads/caps with OEM ones as well at some point, as the NGK ones dont really fit these coveres and required a little bodging to fit.

MPG is still shit, but having read around, I think thats just because its a Bandit 1200 any kind of stop/start urban London commuting gets me about 30-ish MPG at best, longer motorway runs I can scrape 45MPG if Im very economical and ride like a saint.

[redeem ouzzer]

The standard coils and leads are useless. Dyna minis ftw.
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[temeluchus]

[lilredmachine]

[sickpup]

What exhaust is on the bike?