misfiring bike

Hi

I am the owner of a '99 SV650s with 24,000miles on the clock and have a 33bhp restrictor kit fitted and I am getting annoyed at the bike firing on one cylinder.

I've had the carbs adjusted at my local dealer and everything seemed fine but now it is firing on one cylinder when it feels like it. it has had new spark plugs but this doesnt seem to rectify the problem.

The restrictor kit is causing the bike to run rich, as the air intake on the carbs into the engine is restricted. The fuel consumption hasn't gone down and im still getting 50-60mpg, nor is it drinking oil. The restrictor kit cannot be removed until the autumn.

What can i do in the meantime to stop the bike firing on one cylinder??!!!

Any suggestion much appreciated.

[dyzio]

I'm probably wrong thinking about water in front plug.
Check your HT leads and if the HT caps are fitted properly, my sv used to run badly when the caps were lose (and you say you've changed the plugs, so it's possible you haven't fitted them correctly, especially the front one).

This is most likely water getting into the front plug. It is a common problem on the SV.

The best solution is a fender extender and silicone grease on the front plug cap.

Also ensure that the drain hole in the front cylinder is clear.


The restriction washers should not affect the fuel mixture if they are installed below the carbs. As the carbs are CV and the washers have the same effect as limiting throttle opening.

The mixture problems may be caused by something else (or perhaps just by the misfire?)

[dyzio]

V-twin, does this happen in the rain only or all the time?

The problem doesn't happen in the rain, just whenever the bike feels like firing on one cylinder. It makes no difference whether the engine is warm or cold. The HT leads are correctly fitted and it has a extension fitted to the front mudguard.

It's the rear cylinder that cuts out and the spark plug is soaking of petrol and very black in colour, whilst the front cylinder's plug is the normal light brown colour and is not soaking of petrol. And these are new NGK spark plugs fitted less than 500 miles ago

I've even added carb cleaner to the fuel with minimal results. hasnt cured the problem.

One of the connectors to the coil worn/broken/not connecting properly?
Sounds like it's something like that. I think the plug would be blackened if it was misfiring like you said.
Silly question where the gaps checked when new plugs where fitted?

Could be water in the carb float bowls, fit drain pipes to the wee spigots on the float bowls and open the float bowl drain screws a couple of turns, see what comes out.
The screws are a pain to get at, on my raptor I have to take the fuel pump off, not pull the pipes just shift it out of the way.
Some are allen heads and some are plain screw types, I thnk the originals are allen headed.
I do this a couple of times a year, theres always some water from condensation..
If the fuel filler drain pipe gets blocked a lot of water can get in the tank and gives similar symptoms to what you describe.
Cheers
Pod

[ixlr8]

Have you checked the rear plug is working for certain? By pulling it out and holding it against a good earth while cranking the engine and looking for a good strong spark? If no spark, eliminate part by part...plug, lead/coil, connections, ECU...

I have checked the spark plugs and they are firing, this was done recently as the bike refused to start. As of last week it has started first time everytime. Im guessing the problem may lie with the carbs.

does a bike firing on one cylinder wreck the engine?

I had this alot, changed the front HT lead to that off a K3 and runs perfectly now