Maintenance & Technical > KX500 Original

What about 500 vs 250 transmissions?

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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. :lol: 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 :-D

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