Brian & Stef

yeah...unfortunately that's the conclusion I'm being drawn to...another head required I can only be thankful that this hasn't happened on my GSXR Thanks for all the help anyway

...an interesting thought, but the first thing I checked was the oil flow since that is what caused the froblem in the first place. If I remember rightly there are only four holes on the SR head gasget and they are the ones where the head bolts go (not including the big hole where the piston goes....I'm not that daft!!!!)

LOL - I have edited the last post as I forgot to mention that bit, but yes, it snapped that one too!

Sorry - I'll start again...... First head - oil deprivation - mashed exhaust valve and guide - inlet valve was OK Second head - origonal valves - no oil deprivation - straight swap for origonal - snapped inlet valve after a couple of weeks. So - removed broken inlet valve and swapped for good valve from first head. Also used opportunity to replace piston, rings, all top end gasgets (bought them after the oil deprivation as I thought it may have blown a piston). Then - a week or so later, same thing happens to inlet valve. Snaps right where the collets clamp into the groove a the top of the valve. Have never changed anything else on the head except for the valves. To be honest I just thought that the guides were built into the head and didn't realise they were changeable until I read about the 'oven' trick.

Jim, many thanks for such a detailed reply - I have to admit to one thing which may, by looking at your response, be the problem. I simply removed the old valve and plonked another one back in from the original head. I didn't change anything else, just fitted it, gapped it, and hey presto - it worked (for a bit). Other than my failure to grind the replacement in I thought that that was all there was to it.

'98 on an 'S' plate

Hi everybody, hope somebody can help. My sons SR125 recently decided to mash the exhaust valve and guide - thanks to his innability to look at the oil level! One replacement cylinder head later it has developed a habit of snapping the top of the inlet valve - obviously at the weakest part where the groove gets clamped into by the collets. Can anybody suggest what could be causing this strange problem? The oil supply is fine, all springs are OK, the gaps are set according to good old Mr Haynes' manual, but most of all, the valve has complete and unrestrcted access for the full extent of travel. So far as I can tell the cam chain is fine and tensioned correctly, and the cam sprockets seem in very good condition. I am reluctant to just throw another valve in because I don't know if the same thing will happen. After the last change it ran perfectly well for a few weeks, then suddenly, after about 10 minutes of running around at about 30mph (middle of the city, so not thrashed), the damn thing went again. If just getting another new valve (the last one was stripped from another motor) is the answer, can anybody suggest where to get one? Thanks in advance Brian (and Stef the SR killer)