El problemo

[kojack]

Bikes been running great, then with about 40 miles left in the tank topped it up ready for a ride out. Got about 20 miles down the road, then when braking fairly hard, the engine cut out when dipping the clutch to drop a gear.Engine cut back in when the clutch was out ( obviously bumped started ).From then on every gear change down I had to keep the revs high to stop the engine cutting out.Engine just would not idle at all without cutting out. Limped back home el pronto.
I'm thinking fuel problem.Bad batch of fuel maybe.
I put new iridium plugs, and K&N filter in about 6 months ago so would'nt have thought that would be the problem.
Could someone point me in the right direction?

[Juvecu]

Plugs and filter won't cause a problem that sudden. First thing that springs to mind is that it's sucking air somewhere. It could be that the air box connections aren't on properly on top of the throttle bodies. There could be a multitude of other causes, but I'd check the easy stuff like that first. Is is showing FI on the dash?

[kojack]

No other symptoms. when the revs drop red ign light comes on engines cuts out .No fault codes at all.I can start the engine easly but have to keep the revs up to keep it going.

[greywolf]

Maybe you need to bump up your idle speed. 1300rpm is the target. Another common cause is the TPS. Adjust it so it raises the bar at 2500rpm. It may need to be replaced.

http://www.vstrom.info/Smf/index.php/topic,16395.0.html
http://www.vstrom.info/Smf/index.php/topic,13988.0.html
http://www.vstrom.info/Smf/index.php/topic,10241.0.html

[TravellingStrom]

This may be a bit far fetched, and is not a quick fix, but I had a similar problem, but not exact.  But, part of my symptoms were stalling, and I know I had bad fuel, so this post may be of some use.

Mine was caused by bad fuel, and when running it would do what yours did, but with the tank running low, it would kick and fart and stall more often, especially under pressure when riding up hills.

My cause was the low pressure fuel filter, called the STRAINER p/n-15420-05H00

To get to it, you need to remove tank, remove fuel pump from tank, then slide the strainer off and fit a new one, this is what my old strainer looked like compared to the new one, the new one is white!!

[greywolf]

I would think a strainer or filter would affect high rpms requiring more fuel before idle rpms but nothing's for sure.

[Strommer]

Braking hard may have shaken off a hose somewhere?  Alternatively a bad ignition wire may have worked loose.

My suggestion to diagnose would be (in order)

1 Fill the bike with fresh fuel - see if this solves the trouble
2 Remove fairings and tank and airbox - check for loose hoses and wires and check air filter
3 Check plugs and leads
4 Replace airbox and run the bike at idle and shake all the wires (esp. around the front behind the radiatior and in the left fairing) something silly
5 Reattach the airbox and tank - leave the tank elevated and connect eveything except the fuel hose.  Run the bike electrically I.e. don't start it and catch and measure the fuel that flows out.  You should get no less than 350ml in 30 secs by following this routine:  Disconnect the fuel line to the tank & add a hose from the tank outlet to your measuring cup. Turn the ignition key on & off 3 times, giving a small rest period in between (a couple seconds). Each time wait until it stops pumping before turning off the key. If all is well you should have pumped about 9 seconds worth & have somewhere around 350ml in your cup

Report back how you get on as there are lots more people around here with more experience.

Good luck!

[kojack]

Thanks for the suggestions so far. Took the bike out today, started perfectly fine and ran smoothly for about 12miles then, the same problem started,  revs totally dropped off inbetween gear changes, had to over rev to keep the engine going.WEIRD.
I'll strip the bike down this weekend and try some of your suggestions.
Cheers so far.

[Sven]

Just a thought, might be worth checking the fuel tank breather pipe. The fact that you are riding 12 or 20 miles before you get the problem, makes me wonder if you're getting a vacuum in the tank which is restricting the fuel flow. I'm not sure exactly where the breather is, maybe someone else knows?
Or when you get the problem, stop & open the filler cap. See if that clears it again for a while!?

[Juvecu]

Breather is on the right side of the tank, roughly where your right knee would be when you sit on the bike. You can probably see it if you take the seat off and know what you're looking for. The breather goes down inside the frame and ends up going down past the rear brake lever. There will be another pipe with it, it is the coolant reservoir overflow pipe. They pipe out right on the hot exhaust, crazy as that sounds Some people have rerouted the fuel breather for this reason. I've meant to reroute it, but never bothered as it's never given problems in 87k miles.

Sounds like a good call, Sven, I don't think that there is anywhere else to get air from except from that breather (unless the fuel cap lets some in slowly?)

[greywolf]

Do all your bikes have breather tubes to charcoal canisters? On the left side of the pond, only California bikes are required to have them. Bikes sold in other states may have them or may be vented to the atmosphere via the fuel caps.

[Juvecu]

No charcoal canisters on the Wees AFAIK. I think there is a breather on the tank cap (small hole), but I'm not sure if it's just maybe an oil hole of the lock or something.

[greywolf]

If no canister, the caps are vented. I'm surprised to hear this. Euro tailpipe emissions specs are stricter than the USA's including California.

[kojack]

Breather pipe right hand side by the rear brake. sounds promising as I have just renewed all the brake hoses for braided one's. Maybe I've nipped the breather.Will check it out.
Cheers

[greywolf]

If there is no charcoal canister, the tank breathes through the vent cap. The hose on the right side would be the drain hose from the hole in the fuel cap well to handle rain accumulation and fuel overflow, not a tank vent.

[kojack]

cheers you're right.
Looks like I'll be taking the tank off this weekend and checking all the pipes and wires,plus a fuel system check.

[greywolf]

Again, the number one cause is the idle speed is set to low with 1100-1300rpm being the proper range. If everything else is okay, there should be a setting in that range that won't trail off to nothing and won't hang at 2500rpm. If no setting of the idle speed accomplishes that, an intermittently faulty TPS is the next most common cause.

[kojack]

Things are getting a bit more confusing.Had tank off over weekend, checked for loosepipes electical connections especially fuel pump,TPS ,Idle fuel delivery.Everything was as it should be.The problem first started when I topped up the tank.Dueing last week I ran the bike to work ( About 6 mile ) all week .No problems at all.Dueing this weekend it ran great through out all my checks.I had used about half a tank at this point.Today I took the bike out about 100mile no problems ,ran great.Then had to refuel and topped the tank up again.BUGGER! Could not even start the engine at the petrol station without over reving to get the fuel through.Sounded like a bag of hammers as well.So what is it about a full tank that would knack up the fuel delivery.
Just do not get

[greywolf]

If any UK bikes had charcoal canisters, I'd say there was a break in the tank vent tube near the top. I've been assured this is not the case though. I'd still feel more comfortable if a look under the right side cover did not reveal one of these.

[kojack]

No there's definetly not a charcoal filter on the breather.Checked it out today.Breather in the filler cap on the left hand side.
Started the bike today, runs smooth again,and tank is full.So it's only when the engines hot and I fill the tank that the fuel starvation occurs,or it's the filling up that is messing something up.
Think I'm going to have to see a tech because I'm stumped, and run out of ideas.