Modern Axle Blocks for the k5

[Hillclimb#42]

I had an idea for Jfab or Larry Wiechman, or maybe BDI, but my calipers are sucking. I need a new set, or somethin, they won't calibrate right. Maybe one of you guys with a 500, a newer bike and a good micrometer can help us all out...

 On modern bikes like Ktm's and Cr's that we have the axle block is designed to go on two ways. This is so you can change two teeth on the rear sprocket and never change the adjuster bolts. This is very handy because when you are out riding or racing and you want to change gearing, alot of times you don't or can't because it will take too long. The block where the adjuster bolt hits it has two different spec.s out of center. What we need is the difference from center that the sides are, and the overall.  The newer bikes may have different vertical measurements because of varying swing arm designs, but the 520 chain is the same, and going off of the stock block specs and adding the offset for the new style blocks, should be an easy item to add to their arsenal of custom KX items. They work very nicely on the newer bikes, would love to have them on the 500. Anyone know what I'm rambling about?

[maddoggy]

you're saying that you want a custom axle adjustment block with different measurments to center of hole on each side so it can be flipped for different gearing with little to no adjustment needed at the bolt? sounds like a pretty easy item to fab up. i am going to make new blocks for my bike when i finally get my casy cut off my arm. maybe i'll look at trying your idea and see if they work out. my original plan was to make a new left side block and incorporate the flag holder base into it similar to the one BDI posted up a couple years ago. pirate at work here!
                                                                                                                                                       Maddoggy

[Hillclimb#42]

Yeah they are nice on the other bikes. We have a 02 cr250 and the 03 ktm 105 with the same design., except the 105 has 428 chain. They have aftermarket ones out for various bikes, but none that I'm aware of for 500's. Yeah, there's no changing the adjustment, Maddoggy. You still have to pull the axle of course, but that can be out for just a second, flip over your blocks, tighten everything, and you're done. Never even break the lock nuts loose and look at your adjustment range. You can plan on a gearing swap that works, that way too. Sometimes the ideal gear requires breaking the chain or adding a link, which gets into your fun time.

here's a pic of the 105 blocks. Its the only pic I have of one. It has a 49 on it. I can put a 47 on it with how the block is set-up. See how the offset is?

[ktmdude]

I have them on the 09 300, but I don't have calipers. Would a good measurement from a tape (in inches) help? Probably not. Pm me if I can help.

[maddoggy]

hillclimb, i see what you're going for with that. i am going to order some new gearing for my bike, i run 15/50 now and want to go to 14/47 for different riding. when i get my wrist back to 100% i will be working on the new blocks. i'll be sure to post up the pics when finished.

[Hillclimb#42]

Woah,  that may be another thread in itself. 14-47 is too close to 15-50 to ever switch one out for the other, Maddoggy. I always shorthand the math with the theory that one tooth on the front is equal to three on the back. Then you still have to be clear if you are gearing up or down in that math. Most guys change two in the rear like I am saying works well with these blocks. One tooth in the rear is barely noticeable. There is another school of thought, that if you need to change gearing, then just change the front sprocket one tooth, which is definately noticeable.

I have made number tables for hillclimbing using this formula;
Back sprocket teeth count  divide by Countershaft multiply Primary Gear multiply transmission gear = final ratio
                                          Primary on my 500 is 2.680, I always run 2nd gear and thats 1.444
example    47/14 =3.36    x 2.680 x 1.444= 13.002
                 50/15 =3.33  x 2.680 x 1.444 = 12.8997
                49/14 = 3.5   x 2.680 x 1.444 = 13.545
            or 47/15 = 3.13 x same stuff = 12.125

That final drive number represents the number of times the front sprocket has to turn to turn the rear wheel once. So you having that ratio would keep you at 13 :1 Front Sprocket to Rear sprocket. You want to change at least a half of a number, and maybe closer to a whole number to make a noticeable change. It gets pretty deep when you want to figure out all of the choices. Thats how i do it.

[ktmdude]

There is some smart mo fos on this site. My head it still spinning. lol.

[Goat]

Those blocks sound like an excellent idea. If anyone does make some let me know. I would like a set. If I had the machines to make them I would. Make things easier when I change my rear from nobbie (woods riding) to paddle (Dunes) as I run different gearing.

[maddoggy]

i posted the wrong rear sprocket #. sorry, i meant 14/45. i guess i had stock gearing numbers on the brain. i want to lower the gearing some. the 15/50 has always felt a bit higher than i like for all around riding. the 50 is worn out so i will need to decide what other size i want to run when changing as well. heck maybe i'll shoot a little lower than the 14/45 combo for the local riding, and do the 15/50 for dune riding. i'm a little lazy when it comes to gear changing. i tend to just ride wherever with what is on the bike, but i hate riding the current combo locally because the available riding areas are either really rocky/boulder strewn trails or just small tight little open spots. anyhoooooo.........................

[Hillclimb#42]

ktmdude, thanks, but I am not 100% that I'm right on that, but I think I'm close. I am waiting on the real smart guys to say what I'm overlooking. Sometimes its hard to post on here because I want to post correct info, and not guess. Usually some body throws in better facts. I see the countershaft turning 3 point something to turn the back sprocket, but still not getting what the final number is. I need to go back over that stuff. Maybe its turns of the crank to turns of the tire. something like that.

Goat, I am hoping one of our Kxrider machinist buddies will take this idea and run with it, too. I am a carpenter, but I don't think anyone wants them made from wood. I guess I could make a mock-up out of oak.

Yeah, I hear ya' Maddoggy, its confusing. I would say that changing front and rear sprockets, instead of one or the other, adds to the mess. In my way of thinking, 14-45 = 15-48, or 15-50 = 14-47. They are not exactly the same, but close. 15-50 is a bit tall? then you would want like 14-49. Or you start running first longer before shifting. I don't know, its all preference and conditions, like you are saying. I don't change my gearing very often. Its kinda like jetting, once you find the sweet spot, and its finally dialed in, I just do a couple on the back, one way or the other. But each bike likes its own gearing. I did my homework on the charts to see what gearing I needed to pull 1st or 3rd gear holeshots and how close i could get the ratios to 2nd gear pulls. To make a long story short, 1st and 3rd gear holeshots are not close to 2nd gear ones with the standard sprockets, 13, 14, 15, 49, 47, 45.

This is how the blocks look on the Cr. We have a lip on the stock blocks of a kx500. Ours would have to be different design, but same dimensions from center.

[ktmdude]

HC#42, I had the back wheel off last night and pulled a few measurements, no calipers just a metric ruler. 51mm over all, 11mm on the short side to the edge of the hole, 20mm axle hole, and 20mm on the long side to the edge of hole. I am fairly confident in my measurements, I took my time and did my best with what I had. I hope this helps and good luck.

P.s. let me know if you want the height, I would imagine that would be different. (k5 specific)

[Hillclimb#42]

Thanks KTM Dude. Overall should equal both sides added together for the reference. Measuring out of center is the ticket. Thanks alot for your help.

[ktmdude]

Glad to help. Let me know if you have any luck making some. I would be interested in some cool looking green ones for my 01 250. If you are interested in building them and I would not have to cut off an arm for payment, I can get you the height measurement, and axle diameter.

[BDI]

i posted the wrong rear sprocket #. sorry, i meant 14/45. i guess i had stock gearing numbers on the brain. i want to lower the gearing some. the 15/50 has always felt a bit higher than i like for all around riding. the 50 is worn out so i will need to decide what other size i want to run when changing as well. heck maybe i'll shoot a little lower than the 14/45 combo for the local riding, and do the 15/50 for dune riding. i'm a little lazy when it comes to gear changing. i tend to just ride wherever with what is on the bike, but i hate riding the current combo locally because the available riding areas are either really rocky/boulder strewn trails or just small tight little open spots. anyhoooooo.........................

I run 14/45 on my bike at the dunes. I can launch in second and pull fourth gear up the steepest dune on the pipe so the bikes fun for drag racing and that leaves fifth gear for running flat out down the back side of the dunes wich Is is just a tich over a 100 mph. I'm now makeing a touch more HP then when I went through my gear testing phase so I'v been wanting to try 15/47 on my bike to see if it will pull it like I hope. If I pull fourth on the pipe up a steep dune with 15/47 on my bike that will make me most happy  I would not recommend this ratio for a stock bike, Your s**t better be running good to pull this ratio hard in fourth Up a big sand dune with a paddle tire.