major running problem. Suggestions needed

It's not looking good, I'm afraid.
I've now flattened the battery twice and had just one half-hearted cough from the engine for my trouble.
I'm starting to think that Jase22's polite not-quite hints that I was too obsessed with the carburation to consider the possibility of CDU failure were entirely justified. Has anyone had one give up the ghost on them to know what the symptoms are? The only electronic ignition failures I've ever experienced has been with cars, where they go from working normally to not working at all without an intervening period of rough running to mislead and confuse.

Does that humble pie taste nice!!!!

There's something you might want to check before spending a fortune on new coils and suchlike though, have a look at the wiring loom that runs up the side of the subframe. Someone suggested in another post that the wires can sometimes short out on the subframe as the outer wears away.

Electrics can often do stupid things like this, my dad had a CDI problem on his FZR400 recently. His bike was running a bit crappy for a few days, then cleared up, then on his way to work it stalled and would only run at tickover even on full throttle. He stripped it down convinced like you that it was a carb issue as everything pointed in that direction. With a squirt of easy start it fired up and seemed to work fine....for about 5 seconds and then cut out again.

Sounds similar symptoms to yours and his was indeed a CDI fault. Perhaps you could proof this out by borrowing someone's, I'd offer but I'm a little far from Milton Keynes!!!

Add two cloves of garlic, ground coriander, cumin and cardamom, saute with some finely sliced shallots and a little balsamic vinegar, serve with dauphinaise potatoes and humble pie can be made to taste like . . . Humble pie!
When a component fails, why cant it plain and simply fail! Why does the damned thing have to linger, prompting is it? isnt it? is it something else entirely? speculation and thereby leading you up all kinds of false avenues?
I have a horrible idea that a new CDU will cost more than the bike is worth (Second hand CDU's dont appear to exist on E-bay) and as I'm 6'4" and the bike has always been physically too small for me I'm not sure if I should persevere or admit defeat and go on to something else that I might actually find comfortable. Any suggestions?

[northwind]

CDIs go by from time to time on Ebay at about £10... I keep on meaning to buy one just in case, but I never got round to it.

[Spanner Man]

Evening all.
Ditto Sids suggestion re crappy petrol. Also check the HT caps, the front one is particularly prone to getting dodgy.....The other thing worth considering is the dreaded carb icing which is starting to appear now....Get the heaters checked to see that they're working.....Re-locating the thermostat can help.....The stat is the black semicircular thingy with 2 yellow wires coming from it located near the coolant expansion tank. Without having to extend the wires, it's possible to poke it out from under the righthand side of the tank, therefore more in the airstream. Give it a try & see if it makes any difference.

Cheers.

Hello Mike,
I have had a few ignition experiences with my SV and have actually ended up with 2 spare CDIs before discovering that the original was ok!

Some thoughts:
* Although you have changed plugs, etc, you don't seem to have checked if you get a spark or not. This might be best place to start to eliminate ignition or not. Either take out the rear plug and earth it while trying to start the engine (or just take the lead off and insert a new plug, then earth it) & check to see if you get a nice spark. If not, then it is likely a fault somewhere in the ignition cct. 2 people are best for this as it is a little difficult to do the clutch, starter button and hold the spark plug(with a insulated pliers, of course!) - or else tie the clutch in while testing.

* The best way to check the CDI is to remove it and find a fellow SV or perhaps a friendly bike shop might oblige, & try your CDI in another SV. Once you have it out of your bike(The rear body work needs removing to remove the CDI) , it is easy to try in another SV by just taking off the pillion seat, unplug from the CDI & plug your one in loosely. The reason I suggest like this is because if your CDI is blown, it won't damage another bike, & also there is minimum disruption to the other bike.

* Both ignition faults I had were broken wires - The 1st a worn solder joint where the Spyball alarm had been wired into the ignition cct. This was a right ******* to trace as all wiring looked ok when testing with a multi meter, which lead me to replace CDI & even the signal generator & it was only that eventually the soldered joint broke properly that I found it.

* The 2nd fault I have just fixed, but it was complete ignition cut out when sometimes turning corners, going over bumps or just putting the bike in gear! - the engine would cut, lights out, everything dead. That was the main igintion wire in the main loom where it runs from the headlight (Naked SV650) around the steering headstock & then in thro' the frame.

i.e. most electrical faults are wiring faults & not component faults.
George

[Biker Biggles]

I just saw a CDI on Ebay if you need one.Just search SV 650.BTW I agree with testing your one first as these fuel/ignition faults are tricky to pin down.

Lots of suggestions! Thank you! To deal with them in reverse order:

Biker Biggles. The only CDI unit I could find on E-bay is for a pointy. Are they compatable with curveys?

SV George. I do have sparks on front and rear cylinders but I wont know if they're happening when they should until shift patterns at work and other commitments allow me to swap CDI's with a donor (A further complication being that the potential donor is far from convinced we wants to be one. Hopefully your suggestion for preventing damage to his bike if my unit is blown will help persaude him) I dont think a broken wire or dodgy connector is likely to be the cause because, as you say yourself, they tend to cause intermittent, all-or-nothing faults whereas what I've experienced has been steady, if rapid deterioration.

Spanner Man. The problem is quite definitely not carb icing. The original problem occurred on that exceptionally mild day that set new records for November temperatures and I dont think we've had a cold day round here since.
I was convinced that Sid Squid's comments about dud petrol had the problem solved and I could hardly believe it when replacing the fuel didnt cure it. Since then all I've got out of it has been the odd half-hearted cough, but what I have noticed is that it always coughs when I prod the button for the first time in a session. That kind of thing hints at a carburation problem but I cant think of anything to do with the carbs I've not already done or checked.

A final thought. What does the "throttle position sensor"do, how does it do it and what would happen if it failed? Does anyone know?

my 2 pennys worth.......sounds like fuel'air problem for sure, Esp as it crops up when you've warmed up and you've sparks. It also sounds like whoever had he bike before you was very cack handed and probably pulled the thing apart for fun. Have you checked the throttle bodies are securely mounted and there is the correct gasket in place? When cold you were probably alright but as it got hot the expansion weakened the joint to the block or blew the gasket seal. This explains why it was ok at idle....sort of.. but died as soon as you touched the throttle, you maybe pulling in loads of air from a duff seal.....WHAT COLOUR WHERE THE PLUGS? White then too much air/too hot? Black too much fuel or dodgy electrics resulting in unburnt fuel...sorry if this is just repeating stuff..GOOD LUCK!

Plugs were pretty much the colour they ought to have been but looked as though they'd done rather more miles than they actually had, which I assume was a result of the battle they'd had coaxing me home.