Checked the engine over and found an issue that could have been costly.
Missing cam sprocket bolt. The other has loosened so the sprocket moves on the cam as well. The intake is fine, both had loctite and were torqued to the specs in the manual.
Found the missing bolt though when I couldn't turn the engine over by hand and looked down the cam chain tunnel.
Hate to think of the damage it would have caused if I'd tried to start it.
Bolt looks a little beaten up so I guess it was running for a short time with the bolt floating about.
So I now need to find a way of holding the sprockets in place and making sure these bolts don't come loose again.
The valve clearances seem a little tighter than they were so I don't think any piston to valve contact has taken place.