Tourqe I'm about to alter gearing and pulled back wheel out tonight ready for my new sprocket arriving tomorrow

The rear set of gears, called the "Freewheel" are shot, and need to be replaced. You can find another wheel, but this will probably prove to be difficult, or you can pay for a new freewheel or your bike shop may give you an old one for a discount.
Good luck
Joe

Put the bike up on the main stand. Remove the rear brake caliper assy. Loosen the rear axle and pull it out. Now pull out on the wheel, pull it away from the rear gear housing, the wheel will disengage a gear inside and then it is ready to pull out the back.

By the "gear arm" I assume you mean that part of the rear derailer that the chain zig-zags through. This arm moves in two ways. It moves in and out (toward the wheel and away) as you move the shift lever - which is how it changes gears, by moving the chain onto different sprockets (gears). It also moves forward and back (toward the front and back of the bike) under spring pressure. This forward and back motion is necessary to take up the slack in the chain when you are using the smaller sprockets (the smaller the sprocket, the "higher" the gear). When the wheel has been removed, this arm moves forward (under spring pressure) as far as it can to take up all of the slack in the chain. All you have to do is grasp this lever and pull it toward the back of the bike, allowing the lever and the chain to pass behind the sprockets (gears) as you pull the wheel back into it's position. You can safely pull this arm forward and back at any time without doing any damage. One more tip-- I find it a little easier if you first put the shift lever in a "middle" gear position. Then when you pull the wheel into place, you should aim to put the chain on a middle sprocket. You don't have to hit the exact correct sprocket as you can simply lift the rear wheel and turn the pedals forward (after installing the wheel) and the chain will move to the correct sprocket corresponding to the setting on the shift lever.
Good luck! Please vote if you found this helpful. Al K

do it by appliance of science ,TDC no1 then exhaust and inlet valves on the back of the cam so they closed ,now some vehicles have a paint mark on the inlet and exhaust marks on the gearwheel well these paint marks line up so exhaust cam wheel it says inlet so this p?ints to inlet cam wheel and the inlet cam wheel that says exhaust points to exhaust (twin cam per head ) have a play and if you cannot do it then post and i will answer tomorrow as i have a date tonight

remove the left faring undo the water pump mounting bolts not all the bolts around the pump just the two that hold it to the engine case pull the pump out about one inch the undo the sprocket cover and remove put the engine in gear and get somone to hold the rear brake on loosen the sprocket bolt undo the rear wheel axle nut and loosen the chain adjusters to put some slack in the chain then remove the front sprocket and fit the new one on put some lock tite on the sprocket bolt and do up tite with the bike in gear and someone holding the brake on put the water pump on and make sure it is lined up properley when you push it back in it should sit flush to the engine with an easy push.adust your chain and titen all the bolts and nuts and refit your faring.hope the was helpfull please leave feedback.

hi there,

put your bicyles on upside down position,wheel should on top so you can work freelywork on ,then rotate the pedal to check what the problem it should be freely rotating,check break pads if it was engage even w/o pressing control.release brake cable wire to loosen.if not in the break,check the sprocket gear if connecting to the chain belt,check your sprocket release lock,if damage replace sprocket, check the bearing of the two wheel center shafting if worn out replace bearing,on front wheel there are two quick release nuts,loosen and pull out wheel and loosen all nuts and lock plate bearing,pull out shafting with the bearing,examine mostly bearing worn out also shafting in some occasion its worn out also,possible if you want replace one set center shafting and bearing ts not costly,on rear wheel with sprocket it different to disconnect,beacause there is sprocket,you should dismantle the locked plate and lock nuts of sprocket before the shafting assymble same procedure now on front wheel when after disconnecting sprocket on rear wheel.hope this will guide you and solved your problem have anice day.

going to a 42 tooth rear which I'm hoping will fit with a 15 front has anyone managed this without lengthening the chain? i also need the torque settings for the rear wheel axle and sprocket retaining bolts does anyone have them to hand please? TIAI have the 15/42 on mine, it is tight but you should have between 5-10mm of your chain adjustment bolt sticking out of the locknut once it is on and adjusted,,,

going to a 42 tooth rear which I'm hoping will fit with a 15 front has anyone managed this without lengthening the chain? i also need the torque settings for the rear wheel axle and sprocket retaining bolts does anyone have them to hand please? TIAI have the 15/42 on mine, it is tight but you should have between 5-10mm of your chain adjustment bolt sticking out of the locknut once it is on and adjusted,,,

going to a 42 tooth rear which I'm hoping will fit with a 15 front has anyone managed this without lengthening the chain? i also need the torque settings for the rear wheel axle and sprocket retaining bolts does anyone have them to hand please? TIAI have the 15/42 on mine, it is tight but you should have between 5-10mm of your chain adjustment bolt sticking out of the locknut once it is on and adjusted,,,