When pedaling the pedal slips when under pressure as if it has worn teeth and the chain is jumping i have the manual but is not clear 735ekg bike

Replacement Parts for Fitness Exercise Equipment at SPORTSMITH

Using a wrench, you remove the left pedal as you would loosen a normal, left hand threaded bolt. The right side is a reverse thread and would need to be loosened in the opposite direction.

Bike chains are slightly different determined by amount of cogs on rear sprocket. If you havent changed the chain, adjust the tension of chain.If tension is ok-sprocket would be damaged(teeth worn,slightly rounded)but if same prob on different gear, chain tension/incorrect size chain is problem.
Hope this has been helpful..

It may help to have some simple advice about how to shift. You can only shift while the chain is moving. And the chain is only moving when you are pedaling. If you move the levers while the chain is not moving, it is no big deal unless you are very forceful with the shift lever. The bike will simply try to shift once you start pedaling. However, in all cases when shifting it is best to be pedaling very lightly. You want the chain to be moving, but you don't want to be pedaling hard and therefor pulling hard on the chain - that makes shifting very rough and you can hurt yourself. So, you want to shift to a lower gear as you approach an uphill, not while you are already pedaling hard trying to climb it. On the other hand, shifting to higher gears is usually pretty easy since you can always pedal lightly as you are moving fast.

One more thing. If this bike has it's original freewheel (that's the gear cluster on the back wheel) it is likely to be of the old style simple tooth design. These old freewheels are harder to shift than the new ones (basically they are more difficult to shift under pedal pressure than the new ones.) The newer (since around the mid 80's) freewheels have twisted teeth and little indentations in the face of each gear making it a whole lot easier for the chain to climb onto the next larger (lower) gear. If you have the old style freewheel you will be amazed at how much better the new ones work. If you do replace it, replace the chain too.
Good luck I hope you found this helpful Al K

You can't just replace one piece of a worn out drive train. The profiles of the teeth are worn to match the spacing between the links oin your OLD chain.

http://bicycletutor.com/chain-wear/

http://sheldonbrown.com/chains.html

http://www.sheldonbrown.com/brandt/chain-care.html

Proper lubrication and frequent chain replacement can avoid the more-costly parts needing to be replaced.

http://www.parktool.com/blog/repair-help/chain-installation-derailleur-bikes

http://www.parktool.com/blog/repair-help/chain-cleaning-cm-5

okay lets ask why it broke did it get jammed?was it worn?is your front crankset or rear gearset loose with play in it?does the chain make a clicking while pedalling hard? first and last require a replacement chain because it broke for a reason.if your drive gears are loose then you will have to adjust/repair them also checking adjustment on the derailuers should be checked.
hope this helps

Your chain and drivetrain is probably worn out.

Read this...
http://www.sheldonbrown.com/chains.html

needs a new sprocket on the wheel the teeth inside are worn

Rear set teeth may be worn / chain worn and jumps (the bearings-spacers loosen in chain links) / or if you have put new chain make sure its the same length.

Your rear sprocket is worn. As your put the pressure on the pedals the chain is riding over the teeth and makes a crunching sound. The teeth could appear slightly hooked. You will probably find this does not happen in a different gear. You need to replace both the cassette (rear sprocket assembly) and the chain together because the chain wears to match the sprocket and if you just replace one you will still get the slipping. The front chain ring also wears but at a much slower than the rear so check it as well. Also check the rear derailleur that it is tensioning the chain correctly and not damaged or if the bike is a single speed the rear wheel is positioned to give the correct chain tension.

sounds like sand got into the chain, try spraying wd-40 well onto the chain then wiping the exccess