I booked my z750 in at anchor kawasaki for new chain and front and rear sproket, on the day I took rode it in (approx 8 miles) parked it on there forecourt and handed over the keys, I was away for a week so they had my bike for 9 days, when I returned i paid for the work and went to leave, key in pushed starter and it just span over, I went back in and told a group of them, it wont start, i was ignored so I said it again a bit louded, 1 guy came out to the bike and tried and said mmmm it wont start ill get a mechanic, he came out and tried and said sounds like the starter clutch isnt engaging I can fix it but i havent got time now, im in the middle of an mot, so I went home, later that day they left a message on my phone, "the bike has no compression so buy the time you get back to us we would of taken the head off and should have an answer". as i didnt get the message untill that night tne following morning i went in to find out what was going on, my bike was stripped down, the engine was spread all over a work bench and was told that it would need new piston rings and all new valves plus other bits and pieces,I was in shock I asked how it could of happened he said "i really dont no mate its a strange one on me". I left and during the next few days I spoke to trading standards and kawasaki uk, kawasaki uk didnt want to commit to anything and sat on the fence, seemed to me they were siding in anchors favour, trading standards told me to take it somewere else and get a second oppinion, I went back to anchor, they said i wasnt allowed to move the bike untill id paid for all the parts they had ordered, which totaled around £1000 + vat
I called my bro inlaw who is a car mechanic, he came over and had a look and then there was a lot of arguing and to cut a long story short, in there oppinion it was my fault I must of dropped a gearjust befor I stoped and done all the damage, as they would not of started the bike while they had it,
as i wanted to get the bike away from them we aventually agreed that i would pay for the parts that I ( my bro inlaw) thought i needed which came to £230,
Id never go back to Anchor kawasaki findon for the way I was treated and id like other people to know what they are like, and also my son and bro inlaw who both ride as well will never go there again. there customer service is going to cost them our loss of trade , on a good note I went to the corby Kawasaki centre and they really helped me, with advise and other parts i needed to rebuild my bike a friendly bunch off lads who care and went out of there way to help me.

That does not sound right at all.!
You would have to have gone well into the red line to have damaged the valves on a Z motor! Most likely revving the nuts off it and missing a gear - I think you would have remembered doing that!
You are better off getting away from this garage and getting proper service somewhere else.