Maintenance & Technical > KX500 Original

What about 500 vs 250 transmissions?

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don46:
I would have to agree with BDI, dump the RAD, go with the v force, jack up the gearing. We hillclimb in the West, our hills tend to be nastier than the east hills, yours are more like uphill drag races with a couple of jumps, ours are more vertical with ledges and much longer, I run a 15/47-48-49 depending on the amount of traction. You should gear as tall as you can pull. Everybody has a different idea of the perfect powerband, some like it quick others a bit slower. I've tried 4 different ignitions, the stock  90-04, stock 86-89, PVL, and the 01 KX250. Generally speaking I like the PVL, but on the high compression motors they don't like to start due to the low output, the 250 ignition is way quick, like a 250 on steroids, the 86-89 is about the best of both worlds, although I'm looking to add weight to the 250 flywheel to soften it up a bit. Being successful in hillclimbing is being willing to try different things, sometimes they work and sometimes they don't. by the way U2 works

Hillclimb#42:
 Alright guys, I have been putting some strategy to my gearing. At first was in a mind-set that I could make a 500 and a 250 geared the same and they would perform the same. That was a big, NOT! I also had run the same gearing as a buddies CR's. Wrong, try again. I have basically narrowed it down to keeping notes on trial and error for each hill. Notating conditions, tire pressure and the all allusive gear ratio.
  I have the sprocket gearing ratio chart. It goes to the races. I am trying to figure what alot of guys know something about, but never use. I am not racing in long motos or on ice, on sand dunes or harescrambles, but hillclimbing. The idea is to run one gear the whole way. It is a bit like drag racing and motocross combined. Only on a 500' plus hill does anyone plan to shift.
 I have all the transmission numbers gathered up, finally but cannot find the equation for an absolute final ratio. I have found car and even street bike formulas that incorporate tire size and top speed into the equation, but would like to toss those numbers out.
 I see in the manual that multiplying primary drive ratio with final drive ratio multiplied by 5th gear ratio gets you overall drive ratio in top gear. Well, thats a good start, but does the sprocket ratio also multiply to that, to get a rear-wheel drive ratio? The idea I'm messing with is to use available sprockets to adjust gear ratios with enough sense to know which adjustment is the least bit of change, even if I pull 3rd or 1st instead of 2nd.
  So far this is what I'm guessing the equation is, am I right? ;
Primary drive ratio x ratio of which gear I'm in x final drive ratio  x sprocket ratio = overall drive ratio
  The numbers are higher than I thought they would be, especially if that number represents how many times the crank turns to turn the wheel once. Hopefully one of you mechanical engineers are on top of this idea, because the more I know, the less I understand. :? :oops: :x

Paul:
Two files you maybe interested in:

1. The Gearing Chart
2. The Gearing Calculator

Hillclimb#42:
 The gearing chart, I have. That gives a sprocket ratio. I am unable to get the gearing calculator to work. I get an error saying original program source required. I think I have seen it before. Someone else gave it to me, but it was specific to street bikes and their stock gears. If I spent time with it, I probably could have used it. I'll try to find the other link I have to it. :wink:
 Yep, BDI sent me the link earlier in this thread. It is a calculator for street bikes. It includes over 150 models of bikes, and of course it left out the k5. It also incorporates chain links, tire size and a few other specs that I have no clue about.
 I know you guys know how to get more ponies out of the k5, and that is killer. Any lull in the action, I like to buy upgrades and add a little to whats there, but that isn't the direction I'm going currently. I am not dismissing your input about better upgrades and will be applying what I am learning in the future. I just like to understand everything so I can make educated choices and adjustments, and not mess up a good thing.
 I have all ratio info about my bikes, but need help developing that to one final number. So when changing sprockets, it changes the way I need it, and is not like starting in 4th or undergearing the power. You only have two runs per class with no practice.
 Don46 you do what most guys do, and I am sure it is working. Find a combo and stick to that, then tweak with a coulple teeth on back to adjust for traction. I assume it is gear down for less traction and up for better traction. What about a scenario like; you show up to the hill and its extremely slick and muddy, or they have changed your hill from long and straight to rough and add turns. Let's say you didn't bring every sprocket for your bike that covers the needed spectrum. Somewhere in the numbers, in the equation I'm looking for, it seems possible to gear down, but pull third to actually gear up. Or to gear up and pull first to gear down. Even then you probably would plan on a shift, but understanding the ratios, you can add some strategy with less extra parts right?

Paul:
That gearing calculator is specific to the KX500. If you don't have Excel you can open it and work with it in OpenOffice (free office suite).

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