My bike by the numbers, pre-mod

[AZRickD]

Having both completed the KX fork mod, BradF and Krazinski are throwing numbers at me in PMs and e-mails -- all the measurements I have to make to do this conversion correctly.

Sag, rake, trail, distances from axle to axle, etc.

So, I've decided to use KDXRider as a virtual filing cabinet (and maybe snag some astute commentary).

Static Sag: ~ 1.9 to 2.0 inches
Race Sag: ~ 5.5 inches

(I bought the bike set up for 150-pound QuailChaser).

The following measurements will help me figure out if the geometry is similar both pre and post mod. Hopefully this will help me avoid, or dial out, any skittish handling problems that might crop up:

Distance center of rear axle to center of front axle= 56.75"

Rake = 65-ish degrees (measured with a crappy carpenter guage)
Trail = 7-inches (measured from the axle); or 4.5" (from the rear of the fork).

I've also measured from a point on the radiator shrouds as well ( 25-left, 26-right).

Here is a diagram of the Rake & Trail measurments...



The forks that Krazynski will be sending me are rebuilt and set up as follows:

Springs = .43 (my ride weight with gear and Camelbak is @ 224).

Krazy said he went by CC's base valve stack:

24x15 (4)
22x15
20x15
17.5x15
16x15
11x13 (2) (measured .005")
17.5x50 (2)

I should have all the parts I need sometime this week. With any luck, I'll be modded and ready to test next weekend. Ready to ride the weekend after.

Thanks all, for your help.

Rick

[bradf]

His weight is so much less than yours. I seriously doubt either spring will work for you. I hope you are not planning on a rear race sag of 5". You will definitely loose cornering quickness with that. As I stated before in one of those PM's, it is imperatively important that it be around 100 ± 5 mm or 3.9". Once that is set, the measured static sag will probably tell you that the rear spring is too light for your weight. It should be 10 – 25 mm, some like it as high as 30 mm. I would bet you will have to crank the spring down so much it will be less than 10 mm. The static is the indicator of a correct or incorrect spring rate. And as I so eloquently stated in the PM, the .43’s will be too light for your weight. Your race sag on the front will probably be close to 80 – 90 mm instead of the 75 mm it should be. So Rick, go to the MX-Tech or Race Tech site and run your numbers through the spring rate generator.

[AZRickD]

I hope you are not planning on a race sag of 5".

No. I'm simply reporting what it's at now. My very experienced neighbor will have to help me figure out the best way to go about balancing the front and rear once the KX fork mod is done.

the .43’s will be too light for your weight unless you ride very slow smooth trails.

Heck, compared to my stock KDX, I'll be riding on a red carpet. Sounds like at the very least I'll be 90% of the way fork-wise. I'll be interested to see how the rear behaves with the front. I may need to buy a new spring.

So Rick, go to the MX-Tech or Race Tech site and run your numbers through the spring rate generator.

Couldn't find the Race Tech spring calculator but the MX-Tech calculator was excellent.

http://www.mx-tech.com/index.php?id=spring_generator

Here are the results...

Stock Spring Rates:
Fork: 0.37 kg/mm
Shock: 4.9 kg/mm

Recommended Spring Rates:
Fork: 0.45 kg/mm
Shock: 5.3 kg/mm

Recommended Springs:
Fork: 3647046 3647044
Shock: 606226554 606226552

Thanks for more solid advice.

Rick

[IdahoCharley]

My thoughts - the .43 kg springs will be fine IMO.

Your base valve stack could likely lose (2) of the 24X.15 shims for woods riding. Certainly oil height, viscosity, preload and height over triple tree will factor in also.

Your shock spring ~ 5.2 but 5.3 is good also: race sag between `90-105 mm should be close.

[AZRickD]

Yeah, some say that the web-based spring calculators go up one or two compared to the way some single-track riders like it. Might be the same for me... might not.

Time will tell.

Rick

[krazyinski]

Rick keep in mind that the KX forks are longer. The forks will only go up in the triples X a mount . the key to getting the trail close, is going to be sag, how much the front will sag,and how much the rear wont. basically the rear will have to come up to to make the trail get shorter. the rake angle we have no real adjustment for. that 90-108mm is gona be on the 90 mm side of things.
this is what I did SAT was adjust sag with in that range to get the trail inside of 5 inches the OEM specs call for 4.3 inches of trail I am some were in the 4 3/4 inches range.

the reason for so much attention on this is I ride a few different places most are open or what I would consider open single track by the fact you can achieve speeds of 19-20 mph in these areas I didn't notice any negative attributes of the KX forks. My regular spot I ride is tight and desert like rocks and sand a lot of hard pack turns with 12" of sand on top. lots of elevation change and at A or B level speeds you do good to average 15-17 MPH. this is were the monkey shows his head the excess trail causes the bike to corner poorly and unstable not wanting to hold the line. found my self having to square off every corner. thats when I started looking in to rake , trail, spring rate and valving . I like the tight stuff and this is critical if you ride a lot of tight single track.

[AZRickD]

Looks like I'll need a stiffer rear spring.

Rick

[AZRickD]

$109 for a shock spring???

Does anyone know where I can get a 5.2 spring for a 2003 KDX200R, cheap-like?

As for springs for my weight, I'm in the process of losing about 20 pounds. It should take about four months. I'll be fine.

Thanks,

Rick

Edit to add: http://www.monkeybuttparts.com/ had the cheapest price on a shock spring ($92) and the quickest turn-around-time. Two days.

Edit to add: All parts are currently on their way to me. I've only partially solidified a machinist. I might have a working bike over the weekend (although not ready to ride, just ready for testing).

Edit to add: The front is off of the bike. Parts should be in Thursday. Visting the machinist on Friday. I'll use shim stock for the upper TT to stem gap. I'm not sure what I'll do for the nut gap. Maybe shim washers?



KX forks, TTs, wheel and axle arrived today, along with the 5.2 shock spring. I hope the machinist doesn't call in sick tomorrow.

[AZRickD]

Another interesting factoid.

I weighed the KDX front end (fork, clamps, axel, et al) at 27 pounds. The KX? 25 pounds.

If there is a lot of weight in the upper section of the KX fork (and the lower portion of the KDX fork), if the moment-arm of the KX is closer to the rear of the bike, that means an easier lifting front end. My attempts to find center of mass are not satisfactory at this time. :)

Just the difference in weight between the KX TT and stem and the KDX TT and stem was significant. Of course, if a good portion of the KDX weight is in the stem... well, that's staying. However, the KX TT is thinning and has more weight-reducing holes.

I officially handed over the parts to my neighbor who is taking it into his work today for pressing. It's out of my hands. Now I have to find some .020 brass or stainless shim stock. It is .020, right?

Rick

[bradf]

I believe it's more like .027 you need

[AZRickD]

Shim stock is proving to be more of a hassle than I had suspected. None of the hardware stores had it (Ace, Loews, Home Depot). The closest they had were sheets of 28-gauge galvanized steel :(

Hobby Bench had it but only in multiples of .016, (.032, .064).

Frank's Hobby (across town) has .025 and .032 but I can't get there before they close for the weekend. Then I'll be out of town until Wednesday (when they are closed).

Just my luck.

Rick

[bradf]

I have some stainless I can send you.

[AZRickD]

PM with addressed sent.

As always, thanks to the folks at KDX Rider for all the help.

Rick

[AZRickD]

Just got the parts back from the machinist. He had a "fun" time.

Apparently there is a lip on the KDX stem that is keeping the bearing from sliding all the way down to the bottom of the stem (where the thinner KX clamp would require). So, the bearing is not flush with the clamp, but riding against the mini-shoulder of the bottom of the stem. He didn't want to push it beyond that for fear of damage. Should I have him press it on to the bottom? The distance is about 1/10th of an inch.

[Indawoods]

It will be fine... just about all of them are off a tad. Some worse than others but it shouldn't affect the bearing.

[AZRickD]

Thank Gawd !!!

I thought I'd just screwed something up.

So, I either do my final paper for school this afternoon, or I bolt up the KX front end...

Hmmm. What to do, what to do?

Maybe an hour of football and a cold brew first?

Rick

[AZRickD]

I have the parts in place (not yet torqued down) just for eyeballing and measuring.

Note the cool string I used to lash the front brake line away from the spinning spokes of laceration. This is jungle fabrication at its best. ;)



That's my new 5.2 shock spring on top of the front tire (I'm very proud of it). ;)

That 1/10th of an inch nearly cost me a good bite on the steering stop. I may have to fab that spacer that I saw here -- a little piece of metal folded over the stop and mini-bolted to the stop. As it sits, the forks don't touch the left side of the tank, but barely touch the right side.



The 1/10th of an inch also cost me the ability to use the KX stem nut as a spacer. It was too thick, so I had to fabricate some 1"-holed washers as spacers.



That's it for now. I have to go on a biz trip and won't be able to touch it until Wednesday.

Ta-ta for now.

Rick

[canyncarvr]

Just got the parts back from the machinist. He had a "fun" time.

Apparently there is a lip on the KDX stem that is keeping the bearing from sliding all the way down to the bottom of the stem (where the thinner KX clamp would require)

I'm late to this kawfee klatch..but wtf?

The clip IS on the bottom of the stem, right? Please say it is.

The bearing being positioned on the stem as shown..the bearing seal accomplishes what? It's effectiveness is greatly reduced when it's just hanging in the breeze wouldn't you say?

Not to mention the stops. Oh...they already were...

The color on the bearing is a digital artifact of some sort? Actually, the whole bearing looks not worth being pressed onto the stem in the first place. Or not??

Oh..before I foget..the weight part. The KX stem is aluminum, the KDX stem is steel.

If krazinkski used the noted stack...did he keep it? Change it? To what? I've been meaning to take out one of the 24s..but, natch, haven't gotten a round tuit yet.

Let's hear the ride report! (by Wednesday I mean).

[Indawoods]

I think the year of the KX forks makes a difference on how far up the stem goes. The specs are different on the different years. Mine doesn't sit flush... but damn close.

As far as .43 springs working for you... they will work just fine! That is what mine has in them and they work great. Woods takes a slightly lighter spring than what Race-Tech and MX-Tech states.

P.S... The bearing is sealed on the bottom and sits in the races the same... so what difference does it make on it's ability to keep the muck out?

[AZRickD]

CC, remember, you're asking questions of a newbie, but I'll tackle them as best I can. Perhaps you can answer some of your questions for us?

"The clip...?" To what are you refering?

"..the bearing seal accomplishes what?"

The seal is on there rather snugly. And even if was flush up against the lower TT, it would still not be totally supported. I suppose I could apply and build up a butress of low-temp glue to support it underneath from TT to seal if you think it (or some other easy solution would work). As it is, I'll plan on repacking the bearing. If I find it's not working, I can take the whole thing apart and have the stem turned down and a new bearing applied.

Do you disagree with IndaWoods that this isn't a major problem?

As for the odd color of the bearing photo, it's a brand new bearing taken on macro setting with a flash -- the "real" color is anyone's guess. The color might be from the synthetic bearing lube I had on my hands or some other goo I had on my hands.

Krazy said he used the stack noted above (and rebuilt the forks in the process). This was his attempt to make it more trail and less MX.

They are much stiffer than my KDX forks which were so compressed when I sat on it that it didn't have a lot of travel left. Also, the bike "feels" to be sitting a little nose high when I climb on it now with the stiction in the new front and the wimpy stock 4.9 shock spring. I feel like I'm on a chopper, so to speak. I won't do any serious riding until I get the rear spring swapped (maybe by Friday) and I test the behavior of the whole deal on my neighborhood riding area.

I'm a little concerned that the lower fork tubes are pinched in perhaps due to me over-tightening the axle nut or not using the proper width spacers. Remember it's a 98 fork/axle with a 2001 wheel. I tried measuring the top of the lower fork with the bottom to see if there was less distance but couldn't get a reliable read. I'll try again when I get back.