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KX85 Fork Help

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Could anybody help me on how much is the oil level in the fork for 2000/2003 model? Please do not RTFM me as I have no access to the manual. Would appreciate if anybody could mail me on the fork chapter.

Thanks.

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Correct me if I'm wrong, but I believe the KX uses the same 35mm usd Kayabas as a YZ85?

If so, the YZ manual calls for 80 to 120 mm with 90mm being standard. This is from the top of the outer tube with the inner tube and damper rod fully compressed and without the spring. Race Tech also calls for 90mm.

Does your's have a bleed hole in the inner tube? Race Tech and Yamaha differ slightly on the bleeding technique and it involves whether or not there is a bleed hole (our YZs have holes).

Note: At 117lbs rider weight and with stock springs (ideal for 115 lb rider according to RT chart) we found the 90mm to be a tad too much air chamber, so we run a little higher oil level. The forks felt real good, but had just a little too much bottoming tendency on the big jumps. This was more prevalent on the big wheel supermini than the stock bike. That seemed to cure it without affecting the rest of the action.

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thanks for helping out chaindrive

i double checked the manual and here are the official numbers:

2000 (KX80) 80mm

2001-03 (KX85-A) 100mm

2001-03 (KX85-:thumbsup: 90mm

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Many thanks to both of you Frezno and Chaindrive...it help a lot. I will check out about the fork spec.Anyway my sons weigh around 80-100lbs ages from 10 to 16 years old. Is there any advise on how to determine the compression/dampening is optimum? I used to shoot video and watch how the fork and suspension acting during a table top take off and landing. How much gap is needed between the fenders and tires to say that the setting is good. My second son just broke his leg during an overshot last two months. He was just start riding back today. I want to find ways how to set a safe and comfortable ride on the setting. In Malaysia I can see that riders use to set quite stiff for the landing but it lost of comfort and a good traction.

Thanks guy

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Hi zhilmi,

Please don't mistake me for anything like a suspension expert. I'm far, far from it. Looking something up in a book isn't the same thing. I try to read all I can about it, and have been doing what basic hands-on stuff I can. I have learned just enough to realize I don't know much at all. But suspension really fascinates me and I'm not afraid to experiment a little since I feel confident about taking these particular forks and shock apart and putting them back together.

Race Tech has been a good option for me because I can just go to their website, type in my son's weight, preferred stiffness, etc. and just follow their recommendations. Cross my fingers, hope it works. Maybe call for technical advice specific to what I'm doing from one of their shop techs. Try changing things incrementally. Then try to decide if it helped or hurt. It is a good starting point at least, but that's about all.

It's a ton of work and I would hope that part of what you pay for each time you have an expert do your suspension is all of the times in the past he has had to redo something a dozen times to get it right and/or figured out. His education, if you will. The settings that didn't quite work.

There is no doubt in my mind that a true expert like John Curea could do a much better job than I do with the RT stuff, but then I wouldn't learn anything at all and it is impossible for someone like him to watch my son race like I do and to get feedback from him.

That's another big problem: We are talking about a young 12/13 year old. He doesn't really know how to tell what is causing problems or not working right. He will blame himself first since the best suspension he knows is the best he's had (if that makes sense?), which might not be as good as it can get.

That's where a true expert, at the track, is invaluable. You are on the right track, I think, by videotaping your son's suspension so you can slow it down and really see what is going on. Maybe by watching that video, a true expert can guide you, since you live so far away.

The RT site can get you very close on the proper spring rate even if you don't use their Gold Valving (or even their springs), which is just a different approach to accomplish what all of the other suspension companies do, too: Revalving. RT just gives you the option of doing it yourself. No one else does.

I would give much to work with and learn from a true expert. There are so many variables all happening at once. There is (must be?) some logical procedure to it, like first getting the correct springs and setting the sag correctly. After that, it takes a highly skilled and experienced eye to tell what is working right or wrong and which way to go with it (stiffer, softer, more, less, damping, rebound, high-speed, low-speed, front or rear). Throw in the fact that one change usually affects others, and it becomes a real art.

Sadly, unless his dad or sponsor is one of those artists, a rider may never have someone willing to redo and keep redoing his suspension until it is nearly perfect for him. Almost all shops have a good "general idea" of what is needed, but to one extent or another, I would think their efforts are almost as cookbook-style as RT's spring and valving calculators.

You send it to them, tell them the same rider info, and they set it where they believe it should be based on their experience, and send it back. That's where there is no substitute for trackside help, in my opinion.

Good luck to you.

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To make this a little more complicated the KX fork does not have any rebound adjustment, it only has compression clickers. On my sons KX we had MX-Tech install Yamaha internals so we had rebound settings to adjust as well. Did it make a difference? As Chaindrive said the input is coming from a 12 year old which may not be accurate, but it did give us something else to adjust to his liking.

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Hi Chaindrive

Thank you very much for your details explanation.Its been very helpful and I would send a mail to RT. Anyway it is not easy to maintain a YZF, a CR125 and 3 KX80/85. I used to sent all the bikes for any major job to a Chinese mechanic. He rides a WR400 and usually maintain all the local groups' bikes. I feel my YZF fork was quite stiff as I had to set compression at 18 out and dampening at 16 out which is very far from the recommended in the manual.Since I have the manual I dissembled the forks and to my surprise the oil in RH was about 140 but the LH was double which is full. I had serviced the forks and the bearings on swingarm/linkages. Since then I could say I should have done it earlier for the the best ride that I am having now. Next is to check the valve clearance.

Good luck to you too.

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One of the best "Is he bottoming the forks" tool you can get is a zip ty. Just put one on the right front fork. Put it on real tight and in the middle of the fork tube travel section. Clip the extra off and send the little guy out there. After two laps check and see where it is. If it's flat against the bottom, add some compression, about two to three clicks at a time. That will help you set the compression clickers providing the spring is the right rate. I have never had a problem with RaceTech Spring calculator.

If you know he is not bottoming the suspension on landings, look at the bike at the landing point of a good table top. Notice how the bike springs back, both front and rear. If there is a hop or bounce, like a pogo stick, you need to add some rebound (turn it in). You want to take that bounce out. Turn it in two clicks and have him do it again. You should see it progressively getting smoother on the return with less bounce back pogo stuff. Just don't over do it to where it is packing through whoops or braking bumps. Remember Suspension is a compromise of all the obsticles on the track.

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Thanks guy for the advises...its been very helpful...any advise for my short sons.The 13 year need a 5 inches wood block for starting and the 10 year need 12 inches block.

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Tie feet to telephone pole and tie hands to bumper of truck and slowly drive forward. Not too much though or you`ll be looking at buying big bikes for your boys. :thumbsup:

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Wow, zhilmi, one fork had twice as much oil and was clear full?! I'll bet that did feel like crap. That just proves you should never take anything for granted, even on a new bike, but especially on a used one. That is definitely the first step: Check EVERYTHING and put it to stock or known recommendations first. Then see if you have a problem or room for improvement.

That means disassembling the rear shock linkage and checking the bearings and repacking them with good waterproof grease. Take the rear spring off the shock and compress the shock to see if it still has a nitrogen charge or even oil. It should give good resistance upon quick compression and rebound to full extension very quickly and firmly without the spring. You never know if the seal went bad long before or if some joker "checked" his charge by depressing the schrader valve.

Measure your rear spring's free length and compare it to the book specs. Did some overweight rider tire it out? Put your rear spring back on with the set length at specs. Set your clickers to known (stock) specs.

Then move to the front and do the same for the forks. At the very least, dump the cruddy, smelly fish oil out of them and see what else falls out. Then refill them with fresh oil of the correct weight and set the levels to stock specs equally. Make sure the clickers are equal on both forks, too. Finally, set your sag to the correct range. This will also help indicate if the rear spring is too soft or too stiff. It should be able to be set to correct sag while still falling within the correct installed length range.

Now, you have a starting point. You will also be able to more easily detect seal problems, which are impossible to find on a used bike that has already leaked all of its oil out! Don't laugh, it happens all the time.

CR2CRF's zip tie tip is great one. If you rebuild your forks and/or shock, use tight fitting o-rings instead to do the same thing on both the forks and the shock. His advice on determining what's going on and adjusting the clickers for the bottoming and rebounding vs. packing and pogoing sounds very good to me, too.

If the forks otherwise feel good through their travel, but bottom out a little much, try adding oil incrementally and equally (raise the oil level), staying within the recommended range. It will not affect anything except the bottoming and may be all you need to do.

Do not be afraid to experiment with your clickers. Just be gentle when bottoming them all the way in to begin your count out. It is just a needle valve like in a carb and can be easily damaged. Also, when in the middle of their range, clickers do not have nearly as much effect as they do when they are nearing all the way in (or out?). Meaning one or two clicks at 14 out won't change things as much as one or two clicks at 6 out.

All of this is information readily found in your manual, online, and in the instructions when you purchase springs and valving kits. If I am wrong about any of this, or missed something, I hope someone more knowledgeable corrects me. Remember, all of this will just get you to a proper starting point. But that is exactly what you need to do first.

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Hi Guys...sorry for a late reply.My comp hardisk had a crash recently.Anyway...Chaindrive...you did mention manual on-line...any idea of which website do that?

It seem that now I have to spend some time on the bike rather than sending it to the usual could not be trusted mechanic.

Thanks.

zhilmi

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