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KLX suspension build – Picking springs – part 1

Finally! We get to fixing the remaining problem area of this bike to make it a serious trailworthy and desert friendly machine! Come along as we tackle evaluating and rebuilding the suspension on “Katsumi” a heavily modded KLX 250R, which now is sporting a 351 big bore kit, oversize valved head, porting, polishing, flow benched, and electrically upgraded. We will start in this video how to select springs for your application.

Hey hey hey welcome back everybody hey we’re gonna start a new step in the process of working on katsumi and sorry for the background noise here it’s snowing outside today therefore i’m not out freezing in the shop i’m going to show a few clips of riding around on this bike and before we get into the nitty gritty on how to do this i wanted to explain a few things

That are weaknesses of the klx 250 and 300 series family of trail bikes they’re really designed to be an off-road trail bike they’re not a motocross or high speed desert racing type bike and as a result they were designed somewhat out of balance from a suspension standpoint from my perspective the front springs are very very soft they’re actually 0.37 kilogram

Millimeter springs from the factory in the front and they are very soft and in the back it’s a 5.2 kilogram millimeter spring which is almost more on the normal side or the firm side not not really firm but like a motocross bike will have a 5.4 a 5.6 kilograms millimeter spring and it depends on the the leverage of the linkage system in the back and so forth but as

A result this bike is very out of balance the front forks are soft the rear is relatively firm and so the front end just dives under almost all circumstances so that is a big problem and part of what we need to change so before we get into the nitty gritty of what we’re gonna do with this bike this first initial introduction is basically going to be to show you

Some of the free resources you have available to help you do research on the type of motorcycle that you have and before i get too far into this i i want to let you guys all know that the company that provided these parts for me is through duff’s racing want to give props to them and thanks to them for helping me acquire these parts that i need for this bike the

One of the resources that’s available for you out there is a website that represents a company by the name of race tech race tech actually specializes in suspension products for dirt bikes street bikes harley davidsons atvs and now utv’s so i want to show you this website because one of the things that you can do on your own bike to look and see how it’s set up

For the type of riding and train you have is to take advantage of this free resource and what you do is you just simply go to race tech comm and then you’ll click on one of these boxes at the top here you can see my mouse scrolling over here i’m gonna click on the dirt bike and that will take you to to some options here down the left-hand side and what i’d like

To do is just show you one of the many and that is a spring rate search that’s the second box down here on the left and you can actually take a look and see how the springs are in your bike and so if you click on that button it’ll take you to a new page and it’ll ask you to go through and select which motorcycle you have so the first one is the vehicle and it’s

Kawasaki then i’ll go to the next box over here on the right-hand side and i’ll click klx 250r which is the bike that i am referring to and then on the right it has the years 94 95 and 96 and mine’s a 94 and if you click on that button it’s going to bring you up to a new page here that shows you like i don’t know if you can see it very well with this recording

But it’ll show stock fork spring rate and they’ll show you right over here 0.37 kilogram millimeter spring and then underneath that it gives you an option for fork spring series you can calculate the spring and display available springs this is for the forks of course you have it for the shock too but we’ll click on that and that will take you to a new box here

Where you can actually select the type of writing you’re going to do let’s say for example first is the writing type i’m going to select desert because i do more desert writing and then the next number two is your age i’m older than 45 years old so i’m going to click that box skill level and this is where you got to be kind of honest with yourself because it has

A lot to do with where the plushness ends up being in your suspension i usually like to put click on dirt intermediate or expert a class that’s not professional but usually if you’re a hard fast writer you want to make sure and click on that one if you if you like to tend to go slower you’re a beginning writer click on the lower one it’ll ask you for your height

Next i’m standard height or short and then the next one is the gas tank and this is for katsumi so i’ve got an oversized tank so i’m going to click on that and it’ll ask you your weight without your gear there we go 190 and it’ll say calculate spring rate and it’ll load up and it’ll tell you what your fork and your shock spring rates and it’ll tell you right here

On the left the stock spring rate is 0.37 kilogram millimeters and for these modifiers that i just put in there for the type of writing that i do it’ll suggest that you use a point four seven six kilogram millimeter spring or the closest available now the closest available for this bike is a point four six so it would be better if i could have a little bit of a

Stiffer spring but the the firmest spring i can find for this bike is a point four six so that’s what i purchased now on the rear shock down here the stock one is a five point two and it suggests a five point four nine for the closest available since my front springs are going to be slightly softer than what was recommended i went with the slightly softer size on

The rear with ending up with a 5.4 kilogram millimeter spring but so you guys can take your bike think about the writing that you do think about the gear you have on it think about your tank size and all that and you can go to race tech comm put in those parameters and see what your stock springs are and what’s recommended now of course we’re going to be modifying

This suspension a fair bit and springs are just one part of it sometimes if you just replace the springs that makes a significant difference right out of the gate but the other thing you can do is you can go back to the the page that that you started with and it’ll show you all the different things available for your bike for example you can get type 1 gold valve

Kits we showed you that’s what we’re gonna put in this bike for the forks and you can even get one for the rear shock as well it’s got all these different parts you can get your seals you can get your your all your parts you need through them and then your rear shock spring rate and you can get where am i trying to go here i’m scrolling down through your too fast

I think oh there is chuck gold valve kit and you can get that item as well now i went through duff’s racing to get all my parts they’re a dealer fur for race tech and so i like to support duff’s racing down here in utah so i went through them to get these items but so as we start to break down this bike and redo the suspension keep in mind that before we did it

I looked at the spring rates and look at what was available to rebuild the front and rear shock and revĂ© album and we’re gonna basically try to make this bike more balanced and more appropriate for desert typewriting and trail riding which is what i would like to do with it so just keep in mind that as we go through this series and you’re thinking about your own

Bike do a little free research on there and so that someday in the future if you decide to do it you can do it on your own now stay tuned we’re gonna some of these videos are very long and i apologize for that the whole project is finished it worked out great but some of these videos i’m basically going from a to z on each of them so i apologize for it being longer

Than what would be ideal but if you’re one of those guys that’s going to do this yourself i think you’ll appreciate being able to see every step along the way so if you’re not interested in it then wait for something a little more entertaining to come along but so look forward to having you guys come and be a part of this project stay tuned the next video coming

Up we’ll get down to the nitty gritty okay happy holidays everybody peace out

Transcribed from video
KLX suspension build – Picking springs – part 1 By MrDuhfactor