Yep it does sound like you timing is off Ali.
Take off your flywheel casing and flywheel so that you are now looking at the ignition system. There will be 3/4 philips screws holding this on, losen them a bit so that you can move the system to either advance or retard the timing. But befor you do this mark the original position with some tipex so that you know the systems orginal position.
Now because i can't hear the bike i don't know weather there timing is to far advanced or retarded, so you will have to use a bit of trial and error. When moving the ignition system only move it by 2-3mm at a time in either direction so not to get lost and to end up in an either worse position. Keep doing this until you find it running smoothest really, and make sure you have that flywheel tight as a broken woodrough key and thus crank would cost you a lot of money.
While your there it may be a good idea to change the pionts and condenser (i'll get a picture for you) as a poor electronic conection could also be your problem.
Also as said above an air leak around your inlet manifold could be partly due to the poor running but not solely.
Thats all i can think of for now but i'll update if i have any more info that may help. If your still having problems call my dad on 07703357260, he owns a trials bike shop that specialises in twinshockers and he also has over 20 years experience with TYs.
hope this gets you up and running if you have anymore question just ask :)
matt