revtothelimit - motorbike forum

Well I found the culprit of a serious misfire on my Caponord eventually. 1200 v twin with 2 plugs per cylinder. The last plug to be pulled from the fron cylinder revealed this. I've never seen a plug go like this before. My worry was that the ceramic insulator was still inside the bore so I bodged up a hose from the vacuum cleaner and gave it a good sucking out I managed to get it all put back together again with a new set of plugs, cleaned air filter and cleaned up the sensors in the exhaust and reflashed the map using TuneECU. It runs amazing. Had it out for a quick 40 mile shake down last night and all is sweet. So I suppose my question is, what would cause this? The other plug looked exactly as it should do.

Probably just a faulty spark plug.

If it happens again,then it may not be the sparker.

I’ve seen detonation break up the ceramic.

Yeah, knock/detonation can damage the ceramic insulator, but I'm with Skub, probably a dodgy plug.

I didn't know the Capo had a twin spark head.

The Italians love a twin spark head, I was once told when I asked about Alfa T-Spark engine that it was because the wops couldn't design a combustion camber for shit!

Skub wrote: Mon Jun 01, 2020 6:36 pm Probably just a faulty spark plug.

If it happens again,then it may not be the sparker.

This is my my fingers crossed option based purely on the basis that the other plug in the same cylinder is ok. I am reliably informed that the two plugs fire independently i.e. the lower one fires a micro nano second after the top one to complete the burn, so if there was an issue with detonation would it not affect both plugs?
Would any issue of detonation be managed by the ecu to ensure correct timing or could there possibly be a mechanical timing issue that the ecu wont alter?

Am I being unjustly paranoid?

I was out for a wee run again last night and it runs great

Seriously lean mixture could cause that, but it would have effected both plugs and you'd have a hole in a piston.
The two plugs probably do fire at slightly different times to extend the spark time and make sure all the fuel is burnt

Julian_Boolean wrote: Tue Jun 02, 2020 4:08 pm Seriously lean mixture could cause that, but it would have effected both plugs and you'd have a hole in a piston.
The two plugs probably do fire at slightly different times to extend the spark time and make sure all the fuel is burnt

It runs lean anyway. I'm unsure how to richen the mixture using Tune ECU software. It looks like a black art to me. The other option is to fit Fat DUC O2 compensators which interfere with the voltage signal back to the ECU from the two sensors in the exhaust allowing more fuel to be provided. Not a massive job and reports by those who have them fitted they seem to make a considerable difference. Don't seem to be in stock in the UK at the moment. Ho hum.