Motorcycle engine vibrating?

I have a 125 Honda cbr that vibrates badly after about 5500rpm it happens even when the bike is standing still and happens with the clutch in and out even when in gear, I have had it looked at by a mechanic which thought it was valve clearances so they were adjusted and it's still the same, the bike runs ok and rides fine apart from every morning it doesn't start off the starter motor so I have to bump it but this was happening before the vibrating started to happen, it did also burn a full litre of oil within 2000miles which is not normal no smoke comes out of the exhaust when riding only sometimes at startup but if it was the valve seals I'm sure the mechanic would have noticed. The clutch has always been a bit noisy since I've had the bike but the vibrating is that loud that I can't tell if the clutch still sounds the same or whether the clutch noice has turned into the vibrating, the bikes done 17000 miles, 5000 of them hard riding not sure about the rest, oil level is fine also changed the oil, the bike used to slip out of gear and go into neautral but now it slips out of gear but it's still catching I don't know whether there's just multiple different things wrong but it's only 2 years old, does anyone know what it could be?

Check your engine mounts. If the rubbers are worn that's your problem and would cause vibrations all through the frame and handlebars.

First thing first; take-out the spark plug and "read" it…

If you don't know how to 'read', then better learn. It will come in handy for sure. Here's a nice, thorough guide, which I personally find very VERY informative:
https://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/how-do-i-read-a-spark-plug

If spark plug is looking as it should then…

1. Put the bike in neutral and rev it… See if the 'violent' vibration is still there… If it revs normally then inspect sprockets, as they might be worn out… If not, lube the chain…

2. If the engine vibes persists at idle then you may want to get your fuel intake system (In this case, The EFI) checked…

3. Check engine mounts (As someone else have mentioned)…

4. Now, 1 Liter of oil is a LOT for a little 125cc and it could be a number of things:

- Increased wear of piston assemblies.
- Loss of oil rings mobility.
- Valve stem seals don't work.
- Defective crankcase ventilation.
- Oil release in the cooling system.