Very Hard To Change Gears, Please Help

[Tbags]

Hey all,
i will try and keep this long story short

during my off time from work i take on small projects from around the town
one lady asked if i could service her mini bike (lei 125cc) that she had in the shed for many years but never ridden it,

got the bike at the workshop, remove the spark plug and i kid you not, it was like a waterfall coming out of this poor little engine,
apparently her son thought it would be fun to put the hose end in the exhaust pipe and fill it up

Drained and serviced engine, got it running with a bit of messing around, engine runs and starts fine with no issues

BUT NOW!
i have no idea if this was a previous issue, it is extremely hard to change gears but only when engine is running, while engine is off i can get all gears but have some issue getting neutral
i adjusted the clutch including behind the cover plate to help get maximum leverage, but the issue persists,

it is a Zongshen 124cc with 1N234 gear set
where do i begin ?? what should i look for?

 

[my67xr]

so is the bike new, or secondhand to her ?
could the clutch cable be stretched ?
can you adjust it a bit more, a lot of the 125's have a second adjuster half way down the cable too

 

[GooseMan]

Don't know if this would contribute to your problem or not but did you change the oil aswell? water probably got down there is all.

 

[Blender]

I would be pulling the clutch cover off and cleaning the mesh filter, and having a look for and signs of rust and metal chunks, etc.

 

[Tbags]

yea i adjusted all cables places, changed the oil after draining all night, ran it up till hot and drained again
so the oil is clean and new, 4T or T4 i forget which way it is.
if i adjust the clutch any further it slips so i cant kick it over

the bike was brand new when she got it years ago but she fell pregnant around the same time, her friends had ridden it but they do not recall how it was

my thoughts are that something has swollen up due to water and having issues gliding,
i have little to no experience in pulling one of these engines completely down, i have done many gearbox's in my time but mostly earth moving or truck gearbox's

 

[GooseMan]

I'm a deisel mechanic and pulling one of these apart is not as hard as a truck gear box, its all the same really just smaller and more fragile.