What about 500 vs 250 transmissions?

[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.

[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.
 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).

[Hillclimb#42]

 How weak. $2000 computer and can't use it any better than a 5th grader! I may have to wait on the girlfriend to help with the program. Thanks Paul. I'll be trying to get that to work this evening. 

[Hillclimb#42]

 Alright, for anyone who is interested, I think I have figured it out. I actually am surprised at how little overlapping that there is in ratios.
 Anyways here it is.
   1.Find your primary gear ratio. Every bike is different, even from year to year.
   2.Multiply that by the ratio of gear that you are in. i.e. 1st, 2nd, 3rd.... by that ratio, which is also model and year specific.
   3.Then multiply your sprocket ratio. Which is on the gearing chart. Or can be figured by dividing back sprocket by the front sprocket.
 Here is my sample problem for you math haters.

 Primary ratio of 2.68 x Second gear 1.444 x drive ratio sprockets (13-47) 3.62 = 14.009 rpm's to turn wheel once.
I changed to a 14 countershaft sprocket.
 Primary 2.68 x Second gear 1.444 x drive ratio sprockets (14-47) 3.36 = 13.002

The final number, I think, represents turns of the motor to wheel. Whatever it represents gives a number to go by. I have done the math on 13,14,15 with 45,47,49 combinations and compared that with 1st, 2nd, 3rd gear ratios and there is hardly any overlapping of ratios. You think I'm right on the math or am I still off? Before I was throwing a final drive ratio from the manual which represented stock sprocket ratio. Check it out, I'm here for opinions.

[BDI]

some times you can over think things But I like the fact that you are trying to make your own tracks rather than follow In some one elses. You don't sleep at night do you.

[Hillclimb#42]

 It actually stems from me telling buddies that I think I'm under geared. Then I get different answers from everyone, who should know about the cure. Then I want to make an educated change and not a shot in the dark. I started racing to have fun and now it is hard not to be as competitive as possible. Why spend the time and money to show up and get spanked by some 14-15 year old kid. It still happens, but not without me being close. I like making other better riders go for it. I rip the conservitive line and they have to jump the big nasty to win.
 I realize not too many people are looking at these numbers this closely, but there is alot of performance in gearing. The thing is, I don't want to throw a sprocket on there without a clue on why or what its gonna do. The 250 won't thrash me and my pride nearly as fast as the 500.
 I sleep normally, but am usually dreamin about riding, racing or fixing kx's. 
I notice the time on posts is way off, but I'm not sure if thats me or the time where the site is based.
When not riding, racing or fixing I'm jonesin' for it. Isn't everybody?

[BigGreenMachine]

http://www.everything2stroke.com/resource/gear.php


Anyone use this? Is it accurate??

I plugged in the gear ratios for an 88 KX500 and came out with a 76mph top speed at 8500rpm. That right? 

Thats with stock sprockets and a 27 inch tire height.

Someone correct me if I'm wrong. WHat rpm does a stock KX5 max at?

[Hillclimb#42]

 Nice Link BigGreen. Thats more like what I was lookin at. I think the k5 turns more r's, or definately can. They don't list max Rpms in manuals and probably can't. Also any mods in performance, change max rpm. A pipe can shorten max rpms and make it get there faster, or vice versa. I think everything has been dyno'd so its possible to get close to knowing, by finding results of a similar bike. Cranks, piston mods, probably even timing can affect max rpms. Thats where the big money is spent.

[BigGreenMachine]

Lessening rotating mass is the easiest way to increase max rpm, shaving the flywheel for instance.

Max KX500 RPM is around 10000?

[BDI]

What ever you do don't take me the wrong way I like your approach I was just giving you a hard time. I have spent countless nights staring at the ceiling trying to go to sleep thinking about ways to get to the top of the hill faster. soon you will realize just how little the other guys really know and they will be trying to chase you down. It does not surprise me that you baffle people buy telling them you are under geared people just assume to climb a hill you have to gear down and they will gear down and go slower and they will want to gear it even lower trying to go faster. I like to gear It right to the point the bike does not want to peak out In rpms and then back it off a little Or figure out how to sqeez out a couple more ponies to make it pull the gear. keeping the gearing right at the threshhold of horse power Is how you are going to be the fastest. You should try 14/45 It's a tall gear your bike should pull and It makes your wheel base as long as It can be with stock swing arm It's my favorite gearing and I have tried a lot of gear ratios.

[Hillclimb#42]

 That is the next step up in gearing. I'm 14-47 which is pulling 13.002:1 in second and if thats not tall enough then 14-45 is next. That is 12.480:1, which is how I think you need to change things. 1/2 of a whole number at a time.
 I don't take you or anyone else the wrong way. I just sort through the opinions for a common thread or I learn enough to agree or disagree. Some of the answers seem to be throw money at it, but I could spend another 5 grand on each bike, but I'm not loaded. I know what you're saying is right. I have to pull the tallest gear possible without a bog and without being at absolute top rev. The difference is that my gearing is for steep, solid traction with jumps. Where your experience in the sand is telling you that I'm way under geared. I am thinking that I'm close, or at least closer. I also needed the info for adjusting gearing between rounds, if its not. Wish me luck. I'll let you guys know how it goes, rippin this weekend. Later!

[BDI]

I disagree It's my experience with the kx500 that is telling me that you are under geared. I'm not just some sand pansy, I grew up In the nevada desert ridding with my dad and uncles who road things like yz490s'  and TT600s' I road on an 80 they would climb the steepest nastiest rocky hills they could find. If It allready had a trail on It there was no reason to climb It because some one has already done It. If It was something they had a hard time getting up then they would sit there, smoke ciggaretts and drink water waiting for the boy to make it up. You have no idea how many times I have heard "GO BACK DOWN GET A BETTER RUN AT IT AND HOLD IT PINNED" Then as soon as I would get there the rest break was over and It was time to go again that's how I learned to ride no mercy and the fact that I can't find any one who likes to ride with me Is testament to that. I have climbed a hill or two that were not sand. The thing I learned about gearing Is those little asian people know what they are doing and the gear ratios In your tranny are optimized for the engines  horse power output and delivery the gear ratios that work best are not far off of stock gearing I spent a lot of time and money figuring this out sprockets are not cheep. Good luck and go kick some but and take that reed spacer out and give It to a competitor That's free performance