2016 ZX10R, full refresh last year - pistons, valves, retainers, springs, bearings, head milled and .60 thin head gasket fitted, cams degreed. Mapped for pump gas and U4.4. 6 track days and about 5 rounds of racing on the motor since then. All on pump gas except one session where U4.4 was tested. No issues. Show up to cycle jam and the motor starts cutting out, acting similar to like its running out of fuel coming up the hill after 10B during second session of practice on Friday. Limp it around for another lap and pull into the paddock and that's when I start hearing all the funny noises. End of my weekend for that bike. Pull it apart to find this, cylinder #1 burnt up with detonation, piston rings chewed up and rewelded to top of piston. The bore itself is surprisingly ok, no marks big enough to feel with a fingernail. All bearings and journals are good. Valvetrain is good, apart from the dinged up valves. No shrapnel or material found anywhere in the pan or cases. What could have caused this to happen on only one cylinder? I was running fresh non-ethanol 93 pump gas, fuel pump filter was changed with a fresh one the previous time the bike was out on track. Pump gas is mapped to the F map and the bike always defaults to F when turned on so I never mistakenly ran the bike on the wrong map. It's tuned via kit ecu, ignition timing is stock. Bad injector(s) in #1? Shitty luck and spark plug strap or ceramic material broke off and went downhill from there? Granny shifting, not double clutching like I should have and fried the piston rings?
Looks like the plug dropped the ground strap which eventually bounced around around and broke the ceramic isolator and tip of the plug. Just a guess on my part based on what I've seen from my old cager drag racing days. Other cylinders looked good? Based on the witness mark of the good plug your timing looks good. I know I would cut the threads off of the plug and look at the ceramic color and it would give me a good idea on tuning Course I was old school and ran carbs. Bummer. Good thing cylinder bore and bearings stayed healthy.
Looks like more pieces of ring material, I removed the valves yesterday and all keepers/collets were intact
It definitely is, the pistons have high crowns and when you cut the head, you run into clearance issues. I think the analysis above is correct, you broke the electrode and it went for a ride in there. That doesn't look like typical detonation (heat damage), it's mechanical damage.
Thanks for the confirmation, ordered the surface gap plugs specified in the racing kit manual and i'll throw those in once I get the head back from millenium. Also going to get the injectors flow and balance checked at pro-flow for peace of mind. Going to reuse a piston and valves from the previous build that are still in pretty good shape. Funnily enough I know someone who had this same exact thing happen to them on their ZX10R three years ago, at cycle jam. Coincidence or is the back straight and high rpm when leaned over in the kink a perfect storm for this engine and normal plugs?
If you clay the combustion chamber (with a decked head) it's paper thin (1mm or so) where the electrode is. 600 is the same. Pull those plugs and clean them with some scotch brite every couple of rounds and they'll last a surprisingly long time.
Look up detonation. The piston does not appear melted, it appears hammered, it has also been assaulted by a piece of hardened steel slamming into it. This forced the crown to trap the rings in the land and has broken off part of the top of the piston.
