ZX-10R Misfire

[Scotty]

Did a trackday at RAF Odiham today - interesting to be able to get the 10 flat out in top down the runway, good job that it's nice and smooth...

Anyway - experienced my first problems with it today (not bad after 4 years) - After the first session on track I returned to the paddock and noticed that at idle the bike was running on 3 cylinders, with sufficient throttle would get back to 4. In the next session it was really woolly coming off corners, definitely on 3 and then catching onto 4 with more throttle and increasing revs (which didn't make for confidence inspiring corner exits, a sluggish 750 suddenly becomes a full-power 1000 when cranked over...)
The engine is standard, running a filter, full Arrows system and PCIII (it does NOT have a TRE). I pulled in early and started investigating, first looking at the Throttle Position Sensor - didn't appear to be anything amiss with the TPS, when switching on the ignition the 2nd butterflies would cycle, but not close fully until after the engine was running a few seconds - is this normal?

Anyway, I found that the problem was with #1 cylinder (spraying water onto the headers, that one was the coldest). I swapped the plug cap/coil with the one from #2 and the problem remained with #1 (the plug was ok, due for a change, but ok) When the engine was fired up again after standing for a while, it would fire on all 4, then drop to three intermittently as it warmed up, and then I tried it in the final session and as it got warmer it became worse, needing more throttle to catch on all 4 cylinders.

Any ideas anyone? Jam? I don't have a lot of time to get it fixed ahead of Llandow - I wonder if flushing the fuel system through with something to clean the injectors would help...

[TLS-Moose]

You say the plug was OK, but did you actually change/swap it It might give a spark but still fail under load .....

Have you checked all the wiring from the ECU/injectors/coils, etc.

Also, dunno how much of a ball-ache it would be on a ZX10, but can you swap the injector over to see if it's that

[jam]

It could be the valve clearances need looking at. When the bike is warm the clearances close up and cause a valve to not seal correctly leading to a compression loss at low rpm, when the revs rise the compression rises enough to fire the cylinder. First do a compression test to see if that cylinder is low if it's ok when cold then fire the bike up and see if it drops off as the bike warms through whilst the motor is idling. Check the obvious stuff first like the spark plug itself and try swapping that into another cylinder to see if the problem migrates with the spark plug, if it stays on the same cylinder then look at the compression..

[Scotty]

All sorted, put in one of the plugs I took out of the (identical) road bike when I serviced it, problem gone, ran it up to 75ºC on the temp gauge without any problems at all (earlier it was down to 3 cylinders before the temp had reached 50º) New set of plugs ordered today, if they arrive in time tomorrow (Wed) I'll fit them, if not I'll put it all back together as it is now and fit them next week. Bring on Llandow yay!