K3 GSXR 1000 misfire on Cylinder #3

[breakaway]

Intermittent problem with cylinder # 3 misfiring. If I give it heaps of stick, it picks up and goes (especially above about 4-5000 RPM). But lower revs / idle, it bogs down like you wouldn't believe.

It started on friday on my way in to work. It started easy like normal, and ran fine up until I got off the motorway (work is about 15 minutes from motorway). At this point I'd been riding about 15 minutes and the bike was already nice and warm. Suddently, it was running on 3 and farting around, but as long as I kept the revs above 4000 RPM it seemed fine. After work, it started very easily and there were no misfires at all. Rode it all the way home, no worries, so I forgot about it.

Until, now, when I started it for a nice evening pootle at about 6PM, and it ran on 3 cylinders right from the start. I let it warm up to 75°C (normal operating temperature) and it was still running on 3. Took it up and down the road, and it was still running on 3 cylinders.

I know its cylinder 3 being shit because I sprayed cold water on the headers and 1,2,4 dried of significantly faster than 3.

Things I think are worth mentioning:

1. Thursday (day before this misfiring started) was a rainy day, and bike was parked outside with rain falling on it pretty much all day.
2. There is no service history with the bike, other than the fact that I've done an oil change about 500 km ago.
3. I've put less than 1 tank of gas through it in the past 2-3 weeks - it's been parked up most of the time. Is it possible that there has been condensation on the inside walls of the fuel tank and now there's water in the fuel? (Bike lives in covered shed, but its been damn cold recently)

I'm going to put in some new iridium spark plugs tomorrow and see if that solves the problem. I guess it could be a bung coil but I'd like to rule out the cheaper courses of action first.

Any help appreciated.

[Spanner Man]

I think trying new plugs is a good place to start as you say with the cheapest parts replaced first, however from memory this model has the "stick coils" (coils built into the plug cap) and i remember they can give some problems, had a few fail in the past. I'll dig out my notes tonight and see if i can find you some test procedures for the coil to try. This should be the fuel injected model so i should be able to guide you through finding the fault codes and that might enlighten us somewhat.

Will post again later with more useful info.

[breakaway]

If there was a fault code, the FI light would be on right? It isn't

Yeah they do have a coil-on-plug setup. If I change the plugs and get no joy, might try this:



After some googling I found out about another guy who had the same problem - he changed the plugs, and it went away.

[MSTRS:Me]

If there was a fault code, the FI light would be on right? It isn't

FI only works for those things that have monitoring. A faulty plug/cap wouldn' have the requisite sensor.
I had much the same problem with my old GSXR1100 - it was a cracked plug cap. YT's EX500 had similar issue - had somehow lost the little spring clip inside the plug cap, so the cap made intermittent contact with the threaded stud on the plug.
Different bikes, I know, but theme is connector to plug is faulty.

[breakaway]

Ok just finished replacing all the plugs with iridiums. They were only a couple of bucks more than the stockers so I figured I might as well.

Bike is running great now. No missing at all. Have yet to take it for a proper ride but initial impressions are very good.

Thanks for all the help guys! I will try to get some macro photos of the old plugs up later.

[MSTRS:Me]

How many kms had the old plugs done?

[breakaway]

Anywhere from 0 up to 34,000.

No service history at all with the bike. I've already changed oil + filter, now plugs, might do brakes with dot 5.1 next.

Anyway, some piccies:




The above plug is plug # 3. The other 3 plugs weren't in any better condition.

[MSTRS:Me]

Hmmm. That plug doesn't look the best, although the pic is not crystal clear. 34kms is getting up there, but not over the top for plugs to last. Iridiums apparently are good for 100kms. Hopefully that was the problem and you'll be right now.

[bsasuper]

Fingernails need a chop

[j_redley]

Have a look down the inside of the plug to check for carbon build up, its pretty easy to see. You can also try giving it a clean down with some petrol and check for cracks in it, but sometimes these things happen. Fingers crossed that the problem is solved.

[Harvd]

AAAAAANNNND the problem was?

Im assuming plugs but its a bit cruel leaving out the best bit where the bikes fixed and you get to ride away into the setting sun...

[breakaway]

Ok just finished replacing all the plugs with iridiums. They were only a couple of bucks more than the stockers so I figured I might as well.

Bike is running great now. No missing at all. Have yet to take it for a proper ride but initial impressions are very good.

Thanks for all the help guys! I will try to get some macro photos of the old plugs up later.