Loss of power, rough engine

[JamesH]

Hello there,

My 2009 wee-strom has been a great commuting bike, but something is playing up and I wonder if there are any pointers you can give as I've just had an expensive service/mot/replacement rear damper etc and can't afford to send it off to Docs again !

When cold, the bike runs fine. I have a 70min commute and after about 30mins any revs over about 5,500/6,000 give a sudden loss of power and terrible engine noise. Any heavy acceleration gets the same result. If I stop and leave it a few mins (fill up with petrol or go take a pee!) when restarting it is fine and I'm off again. No warning lights come on.

As it's just had a service with new sparks, battery, oil etc. my thoughts are:

Fuel filter - But surely the problem would be constant
Dirty tank - But the same?!
Mixture - I would have expected the issue to be much quicker than 30mins
Heated hand grips - sucking too much battery and not leaving enough to spark, but tried leaving off.
Dodgy HT lead - But would be constant.
Scott oiler - Some weird vacuum/pressure build up from the broken scottoiler (can't fill the damn thing up!).

I don't know !!! Any thoughts on where to begin would be great.

[JamesH]

From what I've read and researched today it sounds like it must be fuel filter. Looks like I'm going to try the external filter hack. Rolls up sleeves !

[oslin]

sounds like it could be the fuel filter worth a check, you can also disconnect the line and measure the output to the manual specs 1.2 litres in 30 seconds I think, did the problem start immediately after the service or did it creep in ?

[tallpaul]

Did this all start after it was serviced? If so I would be checking what they have done. It may be as simple as a plug not properly reconnected.

[Fat Rat]

It could also be a coil breaking down.

[kwackboy]

When this problem arises what happens if you just pull over turn ignition off for a few seconds then turn it back on and start it ..? Does it remain or clear itself . ?
 

[JamesH]

Thanks for the replies, going away for easter but am going to try and measure the output afterwards but the problem I have is I would need to ride the bike until it does it, then somehow manage to do that within minutes of turning the ignition off.

No, it was doing it before the service. I had used some injector cleaner to clear the problem and hoped that a change in plugs in the service might resolve it.

Coil sounds expensive!

If I pull over and turn the engine off it does resolve itself, but only if the engine is off for a few mins, a few seconds wouldn't be long enough.

I had a thought, what do you think? I wonder if I have a lot of crap (I think that's the technical term!) in the tank, as it's sucking fuel through the outer filter it eventually clogs it. Turning the engine off for a few mins would allow those bits to float away only to eventually return after another 30mins'ish.

[Fat Rat]

Your fuel pump assembly very helpfully has a high pressure filter that cannot be cleaned  There is a bypass mod for the older model Wee and Vee. If you think you have rust/crap in your tank you would need to resolve that before paying £100+ for the high pressure filter.

[Fat Rat]

Have a read through this lot  http://www.v-strom.co.uk/smf/index.php?topic=28671.0

[JamesH]

Thanks FatRat, I'll read through that now. I know it's not pressure in the tank as I thought it could be, so I pulled over when it was having the problem, opened the fuel cap and closed it again. No difference.

Yes I've had a look at the bypass mod and totally agree how damn stupid a system it is! It might be worth doing it anyway to be honest while I have it all apart, although I think I will open it all up and clean the outer filter, make sure the tank is clean, maybe pump some fuel the wrong way through the pressure filter and see if that helps. Just need to find time in the busy work/DIY/Kids schedule !

[Gert]

Once you have determined that there is in fact a fuel flow restriction and before you attempt the by-pass mod, there is a you tube video of clearing the high pressure filter, by running the pump for a few minutes with reverse polarity. Some appear to have had success with this. Sorry no link to offer, but it can be googled.

[kwackboy]

I'm pretty sure if you had a pump / filter issue your problem would be happening straight away.
Could be electrical , TPS maybe . 

[claw]

I had and still have a similar problem like your own and have changed and checked many parts. If inside your tank (where the fuel filter, high pressure filter and pump sit) is clean and you have good fuel flow then that should eliminate that. I was convinced mine was a high pressure fuel filter (even though it was clean) issue and done the mod but it made no difference. You just have to check one thing at a time.

[Silverback]

My K7 had similar problems to yours,it was OK when cold but misfired when accelerating and was intermittently cutting out at idle when warmed up.

Replaced the tps and now runs like a dream. I made a test lead up to make it easier to test (see pic). Be carefull though when testing...turn throttle very slowly repeatedly to find any spikes in the readings.  It could be something else causing it but worth testing your tps just to rule it out.

[Octave]

thanks for the photo Silverback.
This test lead is placed in series between the TPS and its harnest, correct?

[Skiddy]

Did this problem ever get resolved?

I had a similar experience with another of my Suzuki's

It would ride perfectly for 20 minutes an then just die, first time was 3rd lane on a busy M62, that was interesting, after stopping for a few minutes it would start and run for another 20 minutes and do the same thing, I obviously bought the bike with this problem 
It took a while and to cut a long story short I found the fault by accident, I had the motor idling with the fuel tank propped up, it started misbehaving and I could see the fuel pipe from tank to pump was collapsing and restricting the flow. After leaving it for a few minutes the pipe regained its shape and ran fine, a combination of tired rubber and heat was the cause.

Of course had I read the service bulletin in the owners manual I would have seen the fuel pipes needed replacement after 3 years 

[Gassoon]

Interesting, Skiddy. So how old was the pipe?

[Skiddy]

The fuel pipes were 6 years old!