Curvy SV650SX misfire from 5000rpm

Hey,

I'm having a bit of problem with my bike (2000 curvy SV650SX) misfiring when it gets around 5000rpm. The only mods to the bike are a scottoiler, fender extender and mirror extensions.



Bit of background...

Unfortunately I don't have a garage so it sat outside throughout the winter. I know this is far from ideal but normally it's not a big problem as it gets ridden regularly for my commute unless it's icy/snowy. Unfortunately this winter was a particularly bad on in the UK and so it sat unridden for a couple of months. I didn't think to take the battery out so when I came to start it was flat. No problem - I just charged it and away I went.
That first ride I eased back into things and had gone a few miles with no problems (bike had warmed up nicely) before I got to the dual carriageway and opened the throttle. As I got to 70mph (around 5000rpm in 6th) it missed a beat a couple of times and then started sounding really sick (so much so that I thought I might've mashed some engine internals!) so I killed the engine, stuck it in neutral and drifted to a layby. I didn't risk start it again and took it to a garage. The electrician initially thought it was a coil that had gone, but after further investigation he said it was one of the connectors under the seat where the tangs on the female spade connector had lost all spring and created a loose connection.


This fixed the problem and it has been running sweet for the last 4 months (mostly in dry weather).

A couple of weeks ago I gave the bike a good clean (wipe down rather than a wash - I didn't drown it!) and adjusted my scottoiler. I don't know if I moved a wire or just ran it on idle too long, but when I came to start it a couple of days later the battery was flat. No problem - I just charged it and away I went.

A couple of days after that I noticed my indicators were being very tempremental - when I went over 80mph they would stop working (left one first, and then the right one a few minutes later). This happened several days in sucession. I'd finish my journey with them still not working, but then next time I rode they were sometimes working and sometimes not working.
I figured it was a loose connection, but wasn't sure if it was related to vibration/heat.

Now the misfiring problem has reared its head again. Luckily I knew it was an electrical this time so kept to the back roads and with the revs under 4000 and got home pretty much OK, tho did miss a beat a few times.

Yesterday I took the fairings and tank off and went over pretty much the whole electrical system, cleaning connectors and spraying them with silicon spray wherever I could. First stop were the fuses - all were fine.

I don't know exactly which connector the bloke from the garage originally found as faulty and he has now retired so I can't ask him. I looked at the wiring diagram in my Hayes manual but nothing has jumped out at me from that. I had a look at the section on the indicators and the relay is the same as the side stand switch (which would cut the engine if it though the stand was down with the bike in gear). I guess the relay could be dodgy, explaining why the two things are linked..? Dunno how likely this is? I guess I could buy another one for £12 and try it, but the terminals on the relay look mint condition so my instinct (for what it is worth?!) suggests the problem is elsewhere. I could be wrong...

I found one single spade connector behind the right rear bodywork (comes straight from the negative terminal on the battery) which could've been slighly loose but I tried wiggling it and even disconnecting it with the engine running and it made no difference.
I found another double spade connector where one of the pins looked like it had slight corrosion, but this is to the fan motor (which works fine) so it shouldn't make any difference.
The only real thing I found wrong was one connector that didn't have anything attached to it. The wiring diagram in my Hayes manual suggests this is for a carberettor heater, but I wasn't aware that the bike had one so that might explain something?!
I also had a interesting moment while I worked out what the dead end connector wrapped in electrical tape was behind the right rear bodywork - it turned out to be the clutch diode. I didn't check it's operation which perhaps I should've done, but the fact that the Hayes manual says it's meant to be like that is a good start.
The last thing I noted was that the yellow wires going to/from the regulator/rectifier were getting quite hot. Is this normal? Could the resistance change in the wire cause the syptoms I'm having?
[photos of the bit mentioned above are attached]

I put everything back and it started OK, tho with a bit of a lumpy idle until it warmed up (probably as I had the fuel lines apart to take the tank off). Yesterday it still had the misfire problem from around 5000rpm upwards.


Yesterday evening I came on the forum to look up about misfires. I found a few posts, but none with the 5000rpm syptom. It gave me a few more ideas of things to check, so this afternoon I took the spark plugs out. I think they're OK (pics below) - tho the front one has a slightly reddish tinge to it.

After I put the plugs back I started the bike and after an initial lumpy idle it revved quite happily upto 8000rpm. I was going to take it for a ride to see if it was OK, but then I heard some thunder so decided against it. I'm not convinced the problem is fixed so I thought I'd type this (which has turned into a massive essay - sorry about that) and see what you guys and girls think. Incidentally, I'm glad I didn't go for a ride as it's pelting it down outside now!

I've not balanced the carbs or checked valve clearances in the 18months I've had it but it's been running great so I haven't felt the need. The fact that it is an intermittent problem suggests to me that it's electical rather than fuelling related but I could be wrong.

From the information I've given, can anyone suggest a particular connector/part of a circuit to check in detail? I don't particularly want to take it to the garage as it should be the sort of job I can fix myself if I can just diagnose it, and I suspect labour might cost a lot while someone else finds the problem.

Any help is appreciated,

Cheers,

Ian

[yorkie_chris]

First thing i would do is bypass sidestand relay, then clean connectors for killswitch and coils.

Went for a ride this evening (30 mins or so), and other than one slight blip early on it behaved itself. Possibly slightly down on power (or maybe I just imagined it), but otherwise OK.

Have to see how it goes, but I'm not convinced I've done anything special to fix the problem. I might treat it to some new plugs as in incentive to keep behaving!

Chris - when you say bypass the sidestand relay, do you literally mean just shorting the connections so all the circuits are completed?
Just re-read the Haynes manual - I thought I remembered it say Suzuki provide no test details for the relay, but this is only true for the indicator part. There is a separate bit on how to test the operation of the sidestand relay so I will probably give that a go at some point.
It's confuses simple people like me by having two completely independent circuits in one little box! And surely this disproves my own theory that the indicator and misfire problems are linked (by the relay at least)...

Still interested to see if anyone has any further suggestions...

Cheers,

Ian

[yorkie_chris]

The relay acts as a switch for the main ignition live... just connect those together.