I have a FSA force light 2x9 crank and want to know which front and rear derailler as well as cassette and chain would be a best fit for this crank

http://www.parktool.com/blog/repair-help

http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

If you changed to a cassette with larger cogs perhaps your rear derailleur doesn't have the capacity for that size.

Crank - No problem
Chain - No problem
Shifters - Compatible only with Shimano R440 or R443 front derailleurs

If you use the R443 front derailleur than it will work with the chain, crank and shifter.

Evaluate what is really happening. The chain has to engage in the teeth both front and rear or it will seem to slip.

If your drive train is original, high-mileage and/or under-maintained you probably have worn gears and a 'stretched' chain.

http://sheldonbrown.com/chains.html

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


Total replacement is the only way to resolve worn

Incorrect rear derailleur adjustment will allow unintentional shifting between adjacent gears which sometimes feels like skipping.

http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

Could be either that your rear derailleur needs adjusting and/ or your chain has an issue such as needing lubrication or replacing.

Best to take into a bike shop and have them look at it.

That is packing grease.......PB blaster or WD-40 spray will take care of your prob.

Of course it can be converted to anything you want - at a price and with some effort. I recently converted a vintage 1984 Cannondale road bike from 2x7 Suntour downtube to full Campi 2x9, carbon crank, yada yada. I like riding it as much as any of the other 3 road bikes I have.

I sourced most of the parts for my various bike projects on eBay. If you're looking for vintage or retro, that's where you go. Just avoid buying cassettes that have been 'slightly' used.

Assuming your bike is still an original 7- or 8-speed, and you want to keep it that way, you may have to hunt around for compatible shifters. Upgrading from 7- or 8-speed to 9 may be the way to go, but then you'd have to get a new cassette (minimum) or a new wheel, or it may not fit into your frame's rear dropouts as the axle spacing crept up over the years with the addition of cogs.

Consider all the individual steps conversion may require; and if each requires yet another modification or encounters a dead end, like frame spacing. At retail prices for parts these days it might be more economical to get a new bike. OTOH, there's no matching the satisfaction of keeping a favorite steed active and doing the work yourself.

There should be one or two limiting screws for the front derailleur that you can use to adjust how far out/in the derailleur moves to shift the chain over. You can ask a friend to lift the back end of the bike off the ground while you do the adjusting of these screws and then try shifting the gear while moving the peddles with your other hand.

Over tim and use, the chain and the rear cogs stretch and shape to form. Replacing the chain usually means replacing the rear cog cassette. If the rear cogs are expensive, then replace the chain more often before it breaks and then you don't have to replace the rear cog cassette

If you replaced the chain yourself , you may have left it too long. With the chain on the biggest cog on the rear and the biggest cog on the front , pull the two ends of the chain together and see where they will link up. Leave another two links in the chain and it should be the correct length. You may also have the wrong chain for the bike. Also carefully check each tooth on each cog front and back for wear. Also check the idler wheels in your rear derailleur.

The rachets in the rear gear cog have gone bad.  Buy a new gear cluster and have it installed on your rear wheel.  about $30