Read this first before purchasing or posting about these shocks, most of your quesitons have been answered here or in the following replies.
THE OEM YFZ REAR SHOCK WILL NOT WORK ON THE 660 RAPTOR, the linkages are opposites.
The 04 on up front shocks are all the same physical size and will all bolt up using one of the discussed methods. The 09 YFZ450R shocks are long travel and will not work with the 660's standard travel front end. If you have a long travel a-arms setup then they will bolt up.
Installing OEM YFZ front shocks are a very common suspension upgrade for other Yamaha sport quads. Here is a little info on them for those in need of answers.
Prices can range from 100 dollars to 600 dollars for a set of OEM front YFZ 450 atv shocks. Dealers, quad shops, and salvage yards typically sell them for 300-600 dollars, ebay price is usually in the 175-250 range and personal classified ads are the cheapest bet at 100-200 bucks. However buying from another individual online is more risky than the other two options so be cautious with who you trust to send your money to. The best forums to try are those devoted solely to the yfz450, but most other forums with a significant sport quad membership will have a set or more for sale as well.
The change in ride height will depend on quite a few factors so not all bikes will be have the same way. Heavier riders and bikes with extended a arms will find the front end will sit lower than others. Preload is the major contributor to ride height, when you reduce preload down all of the way you will be at your lowest possible ride height but you will not have as much absorbtion when you try to land a jump. If you crank your preload way up to the top the bike will sit taller than it did with the stock shocks but you will have a much larger buffer against bottoming out. The settings you choose for this and other adjustments will depend on your bike, your riding type, your riding style, your weight, and eventually your personal preference as well. The best thing to do here is experiment.
One possible method of installation:
Everyone knows throwing a set of YFZ450 front shocks on the Raptor is the ultimate suspension mod for those that don't want to break the bank. I found a used set of 04 front shocks from www.yfzcentral.com
for $120 shipped, I was sold. They arrived within 4 days. Thanks yfz guy whose forum name I forgot! Removing the stock shocks was simple enough, jack up the front end and loosen the bolts. As for installing the 450 shocks, thereís a little bit of modding to be done. First thing you need to do is grind a tiny bit off the top brackets so they fit properly without any rubbing.
Since the yfz shocks are a little longer then the stock you have to cut out a small square in the a-arms to allow the 450 shocks to fit. I took a drill and bored my way through the center upping the bit size each time making the hole big enough for me to fit a grinder in there to square off the hole. This was relatively simple but you may run into problems without the proper tools.
Most installs Iíve seen grind off a bit of the a-arm bracket to allow the shock to fit, I decided to grind off the shock instead leaving the bracket with more metal/strength. You can also grind off some of the bottom part of the shock to avoid having to drill through the a-arms as well.
After that they should bolt up just fine and be ready to ride! There's no doubt about it these shocks work awesome for the raptor and make the ride much better whether you're racing mx or riding the trails.
I give the YFZ450 front shocks a 4...out of 5
Thanks to Doubt for his excellent write up. Please feel free to post any other info or questions you have here in this thread.