Gear jumping

Hi  All... just been out on my 1st run on my lui 75cc, and it keeps jumping outta 4th gear into neutral,  it's OK with  cruising, but when you put a bit of throttle on,  jumps to neutral.. cable adjustment maybe  ???... Any ideas on this  one...Also I didn't realise just how  slow they are on hills.. is this the norm...

Hi Donald, a standard 75cc will probably top out between 45-50mph so it's going to struggle up hills and into strong headwinds i should imagine. I'm not sure on the bhp for standard motors but cant think it would be much more than 6 or 7.
As for jumping out of gear, it could be as simple as cable adjustment or perhaps a taught cable which is pulled when sitting on the bike. Internally it could be a weak selector spring in the layshaft or the gear cogs the wrong way on (i think 3rd is easily mixed up front to back, and somewhere in a book the order is incorrect)
Take a look at the rear wheel to make sure there's no play, if it rocking it could be a loose endplate allowing the layshaft to move making the gear cogs slightly out of line.

Cheers thackers, I'll look at the rear wheel play, and I'm sure I've seen on the log book service, it says gear adjustment quite often, or every 500mls ?? and I'm sure this has missed a few in Italy ...