don't buy the 120 link, that's dumb. The oem chain is 106. To do 13/45, you'll need a 108 link chain. If you want to switch back to stock gearing any time after, just use your oem chain or you could still use your new one since you will gain a tooth up front going back to the oem 14 and the 42 in back so you could use either chain. I know this, because I did it to my KLX. I didn't buy a gold chain, but if you want to waste money on that it's up to you. The chainI bought came from denniskirk.com. It's a partsunlimited X-ring chain that is as strong as the name brands in terms of tensile strength rating. Really, your oem chain is good despite of what some may say. Don't waste it. If you go 13/45 you'll lose your on-road rideability some as the engine spins to 7000rpms at 60mph. If you just do the 13 toother up front and leave the rear alone you'll gain a lot of low end, beable to still use the oem chain,and still have the lower revs at speed. It's a soap opera of sorts. The front sprocket is only $15, while the new chain, Renthal rear and 13 toother up front will set you back about $140. The chain I bought was around $60, the Renthal was $65, and the 13 tooth was about $15. All this stuff was ordered from denniskirk.com and arrived in 2 days. The gold chain is going to be closer to $100 if not a wee bit lower at some places. Also, a steel rear is going to be around $30 less than the aluminum Renthal but of course it doesn't look as cool either imo. Good luck.
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well my friend, i do not own a KTM but do think they are excellent machines. but really, would you buy a size 14 shoe if you weren't sure what size you wore and then cut it down to your toes and sew it up? Well, one can kind of relate that to this. He now knows the size he needs and buying a 120 link chain and dealing with the hassle of cutting down is downright ludicrous imo. But I know, some like to tinker with tools in their garage. I do too, but I also like to plug and play. I kind of like to tell it like it is, and that's just how I saw it. sorry