This one is quite a long-winded one but figure it may help if you have the complete picture....

decided to take the bike out last sunday. she sounded a bit rough when turned her on to warm her up but I just thought it was cold so thought nothing of it. Started to ride and the the throttle was very twitchy. After about 3-4miles, I went to pull in because it didnt feel right and she just lost power.

Pulled over, tried to start her up but nothing. Plenty of fuel so no problem there. Engine is turning over so battery is not dead. Tried with and without choke on but nothing. Got on the phone to MikeST who asked me a few questions and then asked me to put it fuel tap to reserve and then try it.

After a couple of tries, she starts up. Still not sounding great but she's started. Decide to take it for a few miles and see if she is OK. Turn tap back to "on" position and ride off. After about 2-3 miles again, she dies as I approach a roundabout (fecking scary that!!). Again, she wont start up. Turn to prime and then after a few turns, she gets going. Ride her home with it on prime and choke on to give as much fuel as possible to her.

Phone MikeST. Possible Diagnosis: fuel supply problem. maybe something clogging the tap. Try tank cleaner.

Got round to buying some and putting it in tonight. Started her up with tap set to "on", choke on. Starts up fine. After a bit, she starts to chug a bit. I give it some revs and find that each time I do, the revs lag before going up or the rev counter drops. After about 5 minutes in total, she dies.

Set tap to "prime" and try again as I want to try and push through some of the tank cleaner (injection cleaner) and see if that will help. She starts up again but the engine revs a bit sporadically. She settles down after a minute or two and I think great, hopefully its doing the trick. Nope!!!

She starts to decrease in revs. I give her some throttle which she accepts for a bit but then she starts to lose the revs again until she cuts out. Try this a couple of times with it in prime and choke on but same again.


So before I take MikeST's advice and spend a weekend with the tank off trying to sort it. Anyone got any other suggestions on what else i can do or what it may be. Also, once I got the tank off, what should I do (dummy version please).... Mike I forgot what you said to me


Thanking all in advance

Try here to download the manuals for your bike.

http://www.gsfbandits.co.uk/files/

Without looking (i've just bought an 03 Bandit) i reckon that there is eityher a kink or damage to the vacuum pipe that makes hte carbs work, or the diaphram that is insode the tap may be perished. Either way, it sounds as if the fuel isn't getting through properly.


Good luck...

Check for a fuel filter that may be clogging bit is that a carbed bike or an injected one? If it is carbed id check float heights and general cleanliness of the slides. A cracked coil will produce similar results - the crack only showing itself as the engine warms but i reckon its a sh!t in the carbs problem or a stuck float or a stuck slide. take the carbs off - if it is carbed and clean them all out and put them back on. if it is injected then the problem is with the tap or an in line filter.

its got carbs, which were re-aligned a couple of months back by Vaanen so wouldnt think that would be a problem but will look at it.

See if you have a blocked up tank breather, and check the operation of the fuel tap, if the vacuum line is not connected to the right nipple then no matter what your bike won't run any sense. At this stage I would concentrate on just the tank and petcock, and only after the fault has proved not to be here move on to the carbs themselves.

i agree with the above mads, first thing i thought is that maybe one of the vacuum pipes has come loose/split, the vacuum is used to open the fuel valve so if you loose vacuum pressure the fuel wont come through (thats why you had to "suck on a pipe" while i balanced your carbs)! should be an easy job to check, take tank off and check the thin pipes around the carbs, if any are hangin loose or damaged you have your answer, hopefully you can just push it back on again!

also check your tank breather as ancient says, its that pipe that runs down the side to down by the swingarm pivot, there should be a few pipes there, just check they're not bunged up as sometimes they can collect crap from the road, they can also become kinked and stop the flow of air into the tank so the fuel supply is restricted! have you had the tank off recently for any reason?

I hope i havn't knackered your bike! your not hearing any strange noises are you? i think it might be worth another crack at balancing those carbs cuz it was a bit of a rush job in the dark! how has it been up until now, have you riden it much without any problems?

hey vaanen, i dont think its your fault. there has been a strange whirring noise but not sure if its normal. its been riding well up until now without any problems. will check what you've mentioned in the post. if not, you may be getting a call for help!

oh, and no, not had the tank off at all since was round yours. will try and look at it at the weekend if get time.

Sounds very similar to the problems I had when the diaphragm had gone in the fuel tap.

But mine was prolly the original one, years old - wouldn't expect yours to go!

hmmmm, i wonder because the vacuum pressure exerted on the diaphram are very small, maybe while sucking the pipe it damaged the diaphram. shouldn't be too hard to fix...........

right, found some time to open it today and checked the following:

all breather tubes
fuel filter - changed
vacuum pipe


still same problem. whats next?

Quick check for diaphragm in fuel tap - take off the pipe that delivers the fuel to the carbs (take it off the tank end I mean) with the tap in the 'on' position. If fuel drips through, you've got a problem with the diaphragm.

If it doesn't, then it doesn't actually tell you whether you have a problem or not, but at least if it does, you'll know.

If your tap has a 'prime' position, you could see if it runs on prime or if you have the same problem.

A thought just occurred to me - you haven't left it on prime have you? Or on reserve?

BG - nope, not left on prime or reserve. and it does it when on prime too but i think it lasts a little longer before dying.

will check the diaphragm thing tomorrow and post back. any other suggestions on what to check while at it?

Bleeding carbs...oh sorry bleed the carbs...can't do any harm...small screw at the base of the float bowls watch out because fuel will a come flooding out but it does get rid of any crap that may have accumulated..I have not known a bike to die because of this but running really ruff is common.

Anyroad give it a go like I say can't hurt and will be another thing ticked off the list...problem solving is a process of elimination...so get eliminating

diaphragm checked, no leakage.

took off fuel tap and looked at gauzes. all clear, no holes.

next on the list.... bleed carbs... once i find where in the manual it tells me how to.

seems to be running OK at the moment. not sure what it was... maybe a blockage, who knows. if it comes back, i'll be back!!

thank you to everyone for their help and input, it is appreciated