Well the time has come for me to get inverted (forks, that is) as well. I've been wanting to do this since the CR's broke onto the scene with inverted forks back in 1990. I started getting serious about this project a little over a year ago. I measured several of the 250cc motocrosser's forks & quickly ruled them out because they were a tad too long. While I was at a Honda dealer, I measured a CR85's forks and quickly realized that they were the perfect length, but their 37mm diameter was a step down from my 250R's standard 39mm forks. I happened across a "Mini Rider" magazine that had a 85cc shootout, and that was when I saw the perfect set of forks, the KTM 85SX's. They're the perfect length once again, but their 43mm diameter is a step up compared to my stockers. I set up my eBay account to notify me of any 85SX forks for sale and then kept this new found "fork knowledge" to myself, as I didn't want any additional competition when it would come time to start the bidding. Well, I've never seen any of those forks on eBay yet, but all of the other 85's (KX, RM, YZ, & CR) come & go all the time. Then Billy (Honda ATC) let the cat out of the bag with his "Inverted fork ramblings" thread. He now posessed the same inverted fork knowledge that I did! He quickly acquired a set through the KTM Talk classifieds, and now his Z is "Rolling on inverts", as his thread was titled. I followed his lead and acquired a set the same way just after Christmas of last year. I finally got to start the conversion process a few weeks ago, and here's the progress so far.
Pic#1 shows the forks as they arrived, in a gun case no less.
Pic#2 compares the stock, standard fork to one of the USD's. The USD (Upside down) fork is shorter in total length than the stock fork, but when measured from the top to the front axle attach point, they're almost identical. As far as weight, each USD fork leg weighs almost a pound less!
Pics#3 & 4: I've got the spacing set & can start taking measurements for the triple clamps. Luckily, I was able to use the same fork spacing as the stock forks, 10 5/8" on center.
While Billy made all new triple clamps out of steel & changed the fork rake at the same time, I plan on keeping the fork rake the same while modifying my existing aluminum triple clamps. The only other option is to have completely new triple clamps machined, a la Speedbump and his ATCR250R conversion project.
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Originally Posted by HondaATC
Obviously, I'll have to sort that out later. I am hoping to use the stock caliper and just change the mounting bracket, but first I need to get the forks mounted up.
Been there done that. Do you have the KTM clamps where your going to cut those ends off, or are you making all new pieces to weld on? Hows your front fender gonna fit using the original mounts? Mine is kind of a tight fit because the notches in the fender for the forks/fork boots werent big enough for the KTM forks. I kind of had to mount it at a funny angle for it to fit in there.