Originally Posted by
onsay99
Before you spend money replacing the freewheel, chain, or any parts, you might just try
spraying some oil into the body of the freewheel edgewise. sometimes that will free the engagement
pawls to start working again. Worth a try since it has worked for me before.
Take the wheel off the bike and hold it horizontally with the freewheel pointing up. When you turn the freewheel notice the cogs move when you puch them but there is a center part that is fixed to the wheel. Put lube in the tiny gap between the moving and not moving parts. Any VERY thin lub work. Chain lube is good or even 10W motor oil if that is all you have The rotate the gcogs and add lube and let it sink into the gap. Add more and spin the cogs more. Eventualy you have diluted and washed out the dried up crud inside.
It is possible to move and overhaul the freewheel but don't bother. It is a lot of work and the tools needed cost more then a new freewheel. New freewheels are cheap and are MUCH better than the old ones.
The safe advice is to buy a freewheel with the same number of cogs. You can change the number of teeth to suit your ability and the local hills. But many times you can fit on a freewheel with one more cog. Especially if you only have 5, 6 might fit. But I said "might". Check the clearance from smallest cog to frame. if it is about 8mm or more then likely one more cog could fit.
You will need to buy removal tools for the old freewheel and the new one. Buy from Park Tool or at 1/3rd the price but with a longer shipping time from Chinese eBay sellers
Shimano makes some very good 6 and 7-speed freewheels and you can find them on eBay. These new ones have the modern shifting ramps which work very well compared to vintage parts.
If the bike is old, buy a chain. Any 3/32 width chain will work.