What about 500 vs 250 transmissions?

[Hillclimb#42]

 I ride and race a k5 and a 250. I try to set them up the same as much as possible. Hopefully that will make them both as fast and rideable as possible. I put on the same front and rear sprockets on them, and the 250, believe it or not, pulls the the gear farther. That is to say that, I need to shift the 500 sooner on the same hill. Does the transmission in a k5 have lower gears than a 250 or is the power from the k5 able to reach the top of the gear that much faster? I have been running 13/47 on both, but now have the 14 back on the 500. I think that will feel taller than the 250, but I'm not sure of final ratios or if that even matters. Anybody know the difference between 250 and 500 stock 2nd gear sizes? 

[BDI]

13/47 Is very low for the kx500.The transmission gear ratio's do matter. All the transmission gear ratio's should be in your manual's at the end of the chapter that talks about your transmission, you do have manual's for your bikes right I tried that gear ratio on my bike before. I found that the bike slowed down do to the fact I was turning the tire less times per engine revolution that adds up to less ground coverd at any given rpm not to mention the fact the you have to shift more times going up the hill. My current gear ratio Is taller then stock. I like to gear taller and then make more horse power to pull the taller gear rather than gear down to try to make up for a lack of ponies, you will always go slower and your 500 probably isn't lacking any ponies.

[Hillclimb#42]

 I hear what you're saying BDI, and I agree for the most part. I am basically copying other racers on the gearing choice. The object is to run the tallest gear possible with no bog, but a bog on the 500 means you just crashed hard. Understanding that when Hillclimbing the point is not only to make it up, but be the fastest. That means leave it pinned until you are over. On the 250 you have to clutch more to stay off of a bog after a jump, but the stock length 500 wants to flip as soon as it hooks. If you have to let off to regain control, you just lost. I have successfully made the hills, and am leading in points in Indiana and Illinois, but I'm not always the fastest. Of course the 500's fresh motor is not lacking on the power dept., but it seems crazy that the 250 pulls the same gearing farther. Yeah, I have to break out the manuals tonight and see what they say about my gears in tranny. It may actually be better to gear down on back sprocket and pull third out of the hole. I actually just need whatever gear that will spin out of the hole, but one that also pulls on the entire hill without shifting. Also keep in mind we have alot of clay here, which turns hard as pavement with dust on top. Hills often have three breakers on a 150 ft hill. So it is basically three hole shots of 50 ft on average. I'm back to 14/47 and have already been warned by more experienced riders that this may be too tall. So I guess its wheelie time or win time, huh. Thats the only way to race!!!!

[BDI]

I don't hill climb in the way that you do I basicly sand drag up a big sand dune I launch in second and then stab third at the base of the hill grab fourth about one third of the way up and hold it all the way to the top for a smooth ride if all goes right. My bike is loaded and in contact with the ground for the most part. My gearing Is 14/45 and my bike pulls fourth gear up the hill with authority but If any thing happens to cause me to let off my pass is over, so I see your point. Here is a cool tool that takes some patience to use.  .http://www.xs4all.nl/~ator0437/gc/   and this is a ratio chart that might help you make better informed gear ratio changes   http://www.dropbears.com/u/utilities/sprocket.htm   Don't forget your 250 probably turn's more rpm than your 500. If your 250 pulls 1000 rpm more than your 500 it will seam to pull the same gear a lot longer.

[gowen]

I ride and race a k5 and a 250. I try to set them up the same as much as possible. Hopefully that will make them both as fast and rideable as possible. I put on the same front and rear sprockets on them, and the 250, believe it or not, pulls the the gear farther. That is to say that, I need to shift the 500 sooner on the same hill. Does the transmission in a k5 have lower gears than a 250 or is the power from the k5 able to reach the top of the gear that much faster? I have been running 13/47 on both, but now have the 14 back on the 500. I think that will feel taller than the 250, but I'm not sure of final ratios or if that even matters. Anybody know the difference between 250 and 500 stock 2nd gear sizes? 

What modifications have you done to your KX?

[Hillclimb#42]

 250 is all but stock. It has Pro Circuit works pipe and FMF Shorty Silencer. Wiseco piston. Performance on the 250 is largely attributed to the new Kenda tires (Washougal Super Sticky). The 500 is a fresh motor with Boysen Rad valve with a spacer, Pro Circuit Platinum Pipe, FMF Powercore Silencer cut in half, also Wiseco piston. Thats about it for performance upgrades. Also have Clutch ease box, New Clutch discs and steels, steering stabilizer, Super stock clamps, Pro taper bars. There's no doubt, it's a screamer. I have had many compliments on sound and performance, but was thinking 2nd gear is shorter than 250's probably by design. BDI pointed out that the 250 turns more R's so that would make some sense. 2nd gear seems too short, where 3rd will pull until everything goes blurry. I just don't think its possible to pull third off the line. I'm trying to figure out final drive ratio. I have charts on sprocket ratios, but need to figure out that ratio with tranny ratio to get final ratio. To adjust my current set up, I can add a tooth on front, or drop one or two on back and continue to pull 2nd, or gear down the same way, but pull third. I'm too new at it to try something noone is doing, but a little information will help me make small adjustments instead of big ones.

[BDI]

Take out the reed spacer that hurts over rev and is probably why your bike does not pull the gear as long as you would like take out the boysen valve they dont work half as good as V-force.The pro-circuit pipe is good choice but I think the bike makes better power with stock muffler. are you running the thin head gasket the 500 loves compression.  P.S. Dont be scared to try stuff that no one else Is doing If you follow in some one elses tire track's you can't make the pass.

[Arigato]

I read somewhere that for the type of hillclimbing you're doing, gear it to run second the whole way....I can't remember if it was a magazine article or not.

[Hillclimb#42]

 You're absolutely right Arigato. That is the way to win. If you shift it has to be perfect timing. I found out last night that the k5 is actually geared taller in the transmission than the 250 in 2nd. So really comparing the two is apples and oranges. The bottom line is putting the math to it and finding out the final ratio that the individual bike will pull the best. They are just different animals. I will need to pin point the ratio and then have to stay on top of that when making adjustments to make sure I'm tweaking and not making huge changes. The biggest mistake I made so far was to run the same sprockets as a CR 500 and 250 which both have taller transmission and drive gears. Thanks for tips BDI, but I have this k5 as dialed in as I ever have and I don't want to change much now. I am running thin metal gasket, and not lacking compression. The motor is completely fresh from Thomas Racing Service, (Pro Hillclimb Bike Fabricator and Racer) He builds all kinds of bikes for the pros so I'm confident in his abilities to set me up with reliable strong motor. I am just trying to tame it, if you know what I mean. Alot of races are decided by hundreths and even thousandths of a second, so a little improvement is alot.

[BDI]

I understand what you are saying and I do not blame you one bit Im just some yayhoo on a chat as far as you know but I can tell you that the thing's Im telling you about the motor have been learned through countless hours and dollers spent on a dyno by stewart who has spent more time and more money than anyone I have ever heard of figuring out what works and what don't. I know how hard It is to look through the B/S I have been there I have spent years making my bike go faster. With the 500 most people want to detune your bike for you as soon as you tell them it's a 500. My bike will flip right over backwards in fifth gear just by rolling the gas on and it has open desert gearing. On assphalt It wheelies in fifth just above idle and will cary the tire for blocks I call it doing a idle wheelie. But when It really comes down to It, It's all about what makes you feel comfortable good luck and keep on kicken name's and taken ass

[Arigato]

Hillclimb#42...Keep us posted with what gearing you end up with.  What exactly is your set up now?..I'm just curious; I run my bike strictly in the dunes so I have to compromise between max hp and reliability.  It sucks pushing your bike in the sand.

[BDI]

I burn 10 gallons pluss In my bike every time I go to the dunes never ever had a reliabilty problem yet. I usually spend A lot of time fixing other peoples poorly maintained stock bikes. I'm not trying to talk crap I'm just trying to be helpfull you can get a lot from the kx500 with a few well placed mod's.hillclimb#42's bike should come out the hole in second no problem with a 14/45 and easily pull that gear all the way up the hill. Now if every one else in that class is running 13/47 your going to hand them their ass on a platter. Then every one Is going to come over looking at your bike wanting to know what you did.Arigato you go to Dumont right have we not ever lined up at the hill? My bike Is pretty distinctive and people do not usually forget racing It. I don't recall your bike but It looks like you just finished making It all pretty, It Look's good I might add.
   
                     RELIABILITY IS IN THE HAND'S OF THE BUILDER

[Hillclimb#42]

 yeah we ride dunes here for fun and gear up. Its alot different riding sand, though. I am not dismissing that it can pull taller gearing, or that I need taller gearing, but If I was ripping sand with no jumps I might even go taller or build for top end. I am targeting bottom and Mid range plus am riding two differnt bikes,, right after each other. I know there is faster bikes out there, even here. I'm trying to get mine to be mine and like you said before be comfortable, of in my case confident. A good wipe out or loop out is hard on strategy and confidence. I have put the 14 back on and am more confident that it is rideable even though I've yet to race with it. The Cr's I race against have a taller final drive so will be taller, if I match sprockets. If I can keep in the gas, I should lite it up by being taller and stronger.
 10 gallons is quite a bit of riding in one bike. Our sand dune riding is on 750 to 800 acres and gets old after about 4-5 gallons. We usually find a good jump and hit it till we almost eat it and then cruize to the next one. Hills there have ten foot of vert on top where there is hard pack on top layer. You have to be careful going off the top or you may wind up launchin to the moon. I'll keep what you said in mind about the spacer and V-force reeds. Are V-force the best reeds for 250 also? 250 is currently stock reeds.

[Arigato]

BDI, Thanks for the compliments on my bike. I haven't been to Dumont this year.  I was out 7 months due to injury.  The year before that, I went once and there was no one there to race.  We are hitting Coral Pink in a couple of weeks.   

[BDI]

we have big rolling dunes that you can really haul butt on and that's ten + gallons In two days when we go we stay the night.  I have been going to dumont for years and years so I'm sure we have been to the hill at the same time but that would have been on one of my old bikes. It's funny one year I was out there and their was this guy on a cr500 and I was on my 98cr500 that was bone stock even stock pipe. We lined up at the hill and I blew his doors off three times In a row he comes up to me all mad because he's got a pipe,reeds,porting,head work and god know's what else done to his bike and he paid some one to do It all. I sent him packing with a stock bike, I learned a good lesson that day, just because you spend a lot of money on after market hop up crap does not mean your bike Is going to be faster more important Is having a package that works good together and alot of things don't you can have two different things that on their own make more power but together make less. The reed spacer for example lowers your Primary compression ratio which Is the same as shortening your transfer duration and makes the engine run lazy the engine will not rev as fast or as far It just can't because you do not have the primary compression It takes to suport High rpm horse power, not something I want on my bike. Stewart dyno tested a reed spacer I think he might have thrown It away If you want more bottom end and midrange a good place to start Is by having the squish angle on your head recut and cranking your compression up to15:1 by milling It. pore in some vp-c12 and hold on because now its going to come out of the whole pissed off. Now you have the bottom end hit and mid range power you want pluss your bike will rev to the moon because you have good primary compression and yes I think v-force Is the best reed on the market no matter what bike you put It In.
                    You know on second thought listening to me might get you killed