Intermittent Power Loss - K5.

Hi everyone, this is my first post here but I wish it was under better circumstances. I have a K5 sv650 with an intermittent issue which I think is best described as power loss. I first got the bike at 6000 miles and to begin with it would act as if I'd let the throttle snap back to fully off then opened it back up again about once every second for five seconds or so.

I told the garage this and they said run some engine cleaner through it (which I did), it was still under warranty at his point but as it was only doing it once every two thousand miles or so it only did it twice while it was still under warranty. Since then it has got progressively worse (the bike is now at 14000 miles) and now every 20 miles or so (on a constant throttle) it jerks violently back and forth, usually at about 60-70 mph in top gear. It does this for up to a minute or until I press the kill switch and then start it back up again, it will usualy be ok after it has been stopped and started again. If I let the throttle off while its doing this it will stuggle at idle for a few seconds then cut out.

I have taken it to three garages so far (including a Suzuki dealer) costing about £500 in total. Things they have tried are:

Greasing the coils(?)
Changing the spark plugs
Replacing the TPS
Hardwiring the sidestand cut off switch permenantly (it will now run with the sidestand down)

I have also tried disconnecting the STPS and riding it like that but the problem remains.

Sometimes the surging back and forth feels quite gentle but sometimes it is really bad and I can hear slack in the chain being made then taken up hard. It doesnt sound like it is misfiring but its hard to tell especially at speed so I don't know if its affecting one or both cylinders. At tickover the revs sometimes vary and the engine will sometimes cut right out at a standstill. The idle speed is currently set to 1500 rpm but it sometimes varies between 1500 and 900 rpm.

I know virtually nothing about mechanics (it took me ages just to unplug the STPS) and literally nothing about electronics (I would not be ale to use a multi meter for example), I'm wondering now if theres an easy way to see if this is affecting one or both cylinders? Can I remove just one spark plug and run it like that? Is removing the plug hard?

Any suggestions greatly appreciated.

Thanks.

[Bibio]

welcome to the mad house.

when was the last time the oil and filter were changed?

when was the last time you checked the oil level?

does the problem mostly happen when it's damp outside?

First place id look would be fueling, then ignition. It seems Ignition has already been looked at. I have a Carby sv so not familiar with your bike.

Thanks both of you. Bibio, the oil and filter were changed about two thousand miles ago, I have not checked the oil lever for ages but I'll do that tomorrow if that could be the cause. It doesn't seem to matter if its damp or not, the Suzuki dealer took it out in the rain to see if they could re-produce the issue, they couldn't .

rb8989, I'm thinking it might be something electrical because it's intermittent? If both cylinders are affected maybe the fuel pump? That being said at a standstill after a ride today it smelt like it was running rich when the revs dropped which might suggest fuel was getting there but not being burnt?

Thanks.

This would probably be a bit awkward on an SV, but you could try running the bike with a gap between plug and lead. I used to do this on my 125s to make sure the spark is regular and strong ect if I was ever having running issues. If the sparks vary in intensity this should be obvious in the dark. Not very scientific but one less thing to cross off the list. Fueling wise, if the injectors are failing they could be intermittent or you could be losing fuel pressure, especially if the issues occurs in 'sessions'.

[Bibio]

sounds electrical. check the battery terminals and make sure they are tight apart from that its a case of finding the connector that's causing the problem and that could be anywhere.

I had a similar symptoms when I had my SV, it turned out the front HT lead had a crack in (barely noticeable), swapped for a new one and the problem was cured.

Might be worth looking at?

Thanks all, I will check the HT Leads, do you know if I'll have to take the tank right off to unplug them or do you think I'll just need to lift it? Something else which I forgot to mention btw is that the FI light is not on (normally that is, it's on now because I'm running it with the STPS unplugged but I'll plug that back in tomorrow).

Thanks.

My mums sv650 05 plate did this, was a snapped coil pack end in the plug cap, making it connect and disconnect causing bike to go like a rocking horse .