Getting fed up now!!

[CHRIS in MARGATE]

If you drained the gearbox oil and the smoking stopped then you have almost completed your diagnosis; you are leaking gear oil through the drive side oil seal and burning it in plumes of white smoke.
Another test is to run the engine and then stuff a glove or cloth tight over the exhaust tailpipe. If you notice a change in running or it shudders to a halt, then you most probably don't have leaking seals. If it runs without any change then you most probably do have leaking seals.
It's not 100% foolproof but it's a good test.
Might be worth buying new oil seal plate and new screws

[sunrisemac]

When I first rebuilt my GP150 I kicked it over loads of times before I gave it a squirt of oil to bump up the compression and it started , it then proceeded to chuck out a solid stream of white smoke from the exhaust, (which must have really pleased the neighbours), for ages until I took it for a run to get it hot enough to burn all the old fuel that I had got into the exhaust from trying to start it.

[bluebob]

have you made any progress mate.be interesting how you went on with the seals.i am guessing that you have fitted everything the right way,and the fault will be with dodgy parts as it is with a lot of lammy spares.Did you change the oil seal retaining plate?Mine was looking a bit rough so whilst everything else was new I bought a new" british made steel plate",which is still in the garage because it was too thick,so tho original went back in,but I had been advised against the viton seals .
I would listen to the advice about not using silicone on the washer,but this reminded me that when I bought gaskets for mine the halite washer wasn't what I expected when I unpacked it.it was more like what I would call ordinary green gasket material.not what I had been accustomed to.i was assured this was ok,i fitted it and in fairness it seems ok,time will tell.i still don't know if this was a cheap alternative .good luck with your rebuild.

[Stevepshipley]

Cheers Blue,
Not done anything yet, fairly certain oil seals gone but don't know for sure yet or how I'm damaging it.
Just got all the component parts to make a leak tester (as per fearsomeinjuns kit)
My plan is to take the engine out (again!!) and do the leak test and see if the seals gone.
I'll rebuild with Rolf seal and test again before i put it back in the scooter.
I'm on hol next week so it'll be a few weeks before I get it sorted but I will report back in here to the folks who've provided advice etc.

Btw my mate reminded me I replaced his top end a bit ago after he'd holed a piston which involved removing the crank to clean it and replacing the seals. So I did it ok on his engine??? Just this one that's doing my nut in