Having a nightmare here so hoping someone can help. Just been doing some maintenance on the bike and removed the head bolts that go threw the engine. I ordered new long bolts but my head nuts are buggered and aren't offering a decent seal. Now I've spent most of today hunting for these nuts on eBay and I have no idea what size they are. I've tried a m8 nut and whilst it feels like its tightening they feel very loose on the thread. Like they may be imperial. Normally I would just whack it tight and ignore but four loose head nuts = disaster in my eyes. Can anyone shed what these nuts are at all? They're a size 12, which seems odd also for metric that seem to sell as 13 for a 8mm'ish size bolt. Hope you can help
