Questions about KDX I just got

Hey im not KDXer but yeah you do have to mix the gas, 32:1 sounds good. As far as lowend, if the FMF pipe is made for high rpm performance it could hinder your bottom.

Im sure other people on this section can answer your other questions!

Good Luck

Gday Mate,
I own a 1991 KDX so it is very similar to yours, mine however does not have the upside down forks. I dont know exactly why they are better, but I think it has something to do with weight distribution....anyway all new bikes use them now cos they offer much better handling than regular forks. I am not a good enough rider to notice this yet but a good mate of mine reckons they are the best innovation to the biking scene ever!

I have seen 5 or 6 KDX's first hand and none of them use the auto mix oil feature, mostly because this is inferior to premixing youself. What ratio to use is a hotly contested debate, personally I use 40:1 and have had no probs so far!

As for Low end power, I too have been dissapointed with the KDX. I came off an 86 IT200 into my KDX and so far the IT had far, far more low end torque than the KDX. They’re not even comparable. I pulled my bike apart and found out the entire KIPS setup was missing, so I replaced it all with brand new stuff and it was still too sluggish below power band. Last night I gutted my stock pipe as per the instructions on the KDX home page (easy job) and its currently getting pickled before I weld it back together and tune the bike for it. Im expecting a significant boost in power, but seeing as your bike has an FMF pipe on it I am now a little concerned, the bike should pop mono’s easily in first and second in my opinion (My stock IT did).

i have a 91 kdx 200. with the stock pipe on my bike, boysen reeds, wiseco prolite piston, removed airbox lid, and all new kips assembly my bike had decent torque down low. after i crashed and crushed the pipe and got a fmf fatty i lost a little more bottom but am not sure it is completely due to the pipe because i discovered my kips valves are siezed once again. reguardless i can still lug it and with very little clutch feather bring the front up in first second and third with little effort. i am also running a 40:1 mixture. with proper jetting the kdx is hard to beat in the woods. remember to keep your air fliter clean too. your reeds could also be to blame for your power loss. if they need replaced go with boysen power reeds. theyre dual stage and make for crisper throttle response.

Inverted forks are "better" because they are more rigid (less flex). The point of most stress is right below the lower triple clamp. When you invert a fork you put the larger diameter outer tube there, which gives it a strong advantage in resisting flex. There are pro's and con's to everything, but almost every bike sold today has inverted forks, except play bikes, where low cost is more important that top notch performance.

pmullins said:

Or maybe I have gotten too used to four-strokes riding the Honda. .

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While you're making sure everything is right with the KDX, I wouldn't rule out some four-stroke backlash. I just got back into riding two years ago after being away since the mid-70's. I've been buying old, cheap bikes and turning my own wrenches. So far; '77 TT500, '77IT400, '75 XL250 (package deal with the IT400), '80 KDX175, and most recently '78 IT400 (thrown rod destroyed the '77 bottom end -- it's now a parts bike).

The XL was a heavy, old, underpowered, undersuspended dog, but handy for inexperienced friends. It also always started and ran. It had to go though for the sake of marital peace. The TT500 was strong and loaded with torque, but heavy. It was much harder to part with, but it had to go too before I could bring the '78 IT400 home from a friend's garage where I was hiding it.

I still miss that 500 some! The concept of low end is just different with a four-stroke! Even with the big 400 two-strokes (and I found the first one scary fast until I got used to it), with plenty of bottom, low end is mostly there to get it onto the pipe. Not so with the four-stroke! A four-stroke just pulls all the way until the powerband ends, with little 'punch'.

My KDX was very dissapointing in the low and mid-range, particularly coming off of the TT500 --- though I found I had a very minor air leak at the intake manifold, which the last owner missed and tried to jet and tune to compensate for. It seems much better since I fixed it, but now I have to dial in the carb for proper air draw (it's now way too rich). My best friend rides an '82 XR175, and he could always take me off the line or out of the corners. Then I'd catch him with the RPM screaming. This weekend we'll see if that's changed!

I've riden the XR175 around the place we go a couple of times now, and it's a fun bike, and reminds me of the TT500 a bit. The power seems quite adequate, but it really never seems FAST. You need a lot of displacement before a four-stroke gives you that feel (at least an older one). A two-stroke can do it with much fewer cc's.

A certain writer who you probably read in the 70's, and who now writes a Q&A for another online publication, swears that the KDX200 is the best all round dirt bike ever made! And he's riden and raced pretty much everything over thirty some years.

adam728 said:

Inverted forks are "better" because they are more rigid (less flex). The point of most stress is right below the lower triple clamp. When you invert a fork you put the larger diameter outer tube there, which gives it a strong advantage in resisting flex. There are pro's and con's to everything, but almost every bike sold today has inverted forks, except play bikes, where low cost is more important that top notch performance.

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I agree that there are many advantages to inverted forks, and also agree that you put the "better" in quotes to qualify the fact that sometimes "better" should be looked at on a case by case basis :)

I have riding friends with inverted forks who ride moderately hard and its standard operating procedure for them to have replace fork seals once a riding season, sometimes even twice in a riding season. A few of those people have had KDX's or other bikes with "regular" forks and have stated that they could go sometimes 3 or 4 seasons without even looking at the fork seals.

Also, if your inverted fork seal fails, your fork basically empties itself of all fluid... On regular forks you get a little mess, you keep riding and just remind yourself to fix it later after you get back from the ride...

Sometimes forks can be "too stiff" or rigid... I've had several people tell me that rigid forks are great on the track, but that the prefer the feeling of regular forks on a technical trail ride... Something about smoother/dampened response being more advantage many times over rigid, what they called low speed twitchiness.

There is very little advantage concerning unsprung weight, as the spring housing compared to the fork shaft on a fork are comparable in weight...

Big advantage to the inverted forks besides the coolness factor is that they don't have the overhang that can often "hang you up" :) in deep ruts or going over other obstacles.

I won't argue the fact that I believe that in most cases, inverted forks are superior. They do have a slight advantage in unsprung weight (though not as much as many claim), They have excellent clearance, and if rigidity is the target, they are significantly more rigid...

But given those criteria, What YOU are looking for in fork performance might center more on technical low speed trail riding where you might want to try to avoid fork rigidity and HATING to work on your forks :) In that case, the regular forks are excellent choices!

I think alot of the reason that inverted forks have such great potential performance characteristics is because they are the technology "du jour" and many companies are pouring research/materials and design into them and very little on regular forks...

In the end, riding ability will outstrip just about any technology advantage in most things including bikes, and fork design disappears into insignifigance in all areas except reliability and the ability of the fork to KEEP you riding :) I was at Carnegie once and saw this guy blasting by EVERYONE and he was on this super old looking dirtbike with upright dual springs in the rear with about 3 inches of travel! It was unbelievable how fast this guy could ride and how he could outclimb everyone and anything on all but the very steepest bumpiest climbs! Its kind fo like that old saying "Gene Autry on a Ukelele sounds better than me on a $5000 guitar" :)

Just a newbie's view anyway...

Have a good one!

Feanor

good day!!! how much will it cost the entire kips to be replace ? i have a 1989 kdx 200 and i found out that the kips is no longer working. can you plss guys there help me? thanks!!!!!!

I've got a 93 too!

Not knowing what is involved with rebuilding the KIPS valve can be intimidating but it is not really that difficult. I would first suggest that you purchase a service manual for your KDX E-model it will cover rebuilding the entire machine from 1989 thru 1994. You can look on line at Powersports parts fish CLIK HERE and get a rough price for the parts. But before you assume that the KIPS valves are stuck you need to pull the pipe and the little grey cover on the right (throttle) side of the cylinder to confirm that the valves are functioning or not. Take a flashlight and look up into the exhaust port and at the same time gently rotate the nut on the shaft that you exposed when you took the cover off. Look up high in the middle then to the right and left while moving the nut. If you can see the valves rotate and open up to a slot cut in them, then your KIPS is working.
If you don't know the engine history of the bike you may as well assume the reeds are worn and could be taking away some of your low end and should be replaced with Boyesen Power Reeds that cost between $30 to $40 US.
How many teeth are on the front sprocket? A 12 tooth makes a big difference over the stock 13 and cost about $10.
I ride at around 700' above sea level and use a 152 main jet, 40 pilot, BGL needle with the clip 4 notches down from the top, no lid on the airbox. Get rid of the BR9ES spark plug and put in a BR8ES even though the 9 is recommended. I run my premix at 40:1 and use Mobil 1 MX2t, I have done the pipe modification described in Canadian Dave's Tech Tips and over all I would say I have great torque off the bottom! It will never be a four stroke but I've ridden many that don't pull as well from Idle as my KDX. I used to have an XR500 loved the low end but it was obnoxiously heavy the suspension was poor and I hated starting it when it was hot, It sprained my ankle once when it kicked back.
Oh yeah the upside down forks have a lot of potential, I put heavier springs in mine and revalved them as they are the cartridge style like the newer forks. I like mine because they are very stiff and precise no flex perceptable.
There are other tricks to get more precieved low end, like a flywheel weight or advancing the timing.
Get her running right, jetting and so forth you won't be dissapointed in the low end torque! You might, however scare your self :yikes:

I have a 94 same as yours the bike is old i and you need to change all things old like fork oil that would make them much better and those forks are good up side down,GOOD.the kips,one is always bad thay are easy, get a manual keep it clean. Bike bandet has the kips valve about 37.50 each good deal keep them clean thay will lastwen mine was new thay said to recharge the rear shock,can`t rember how much,boisen rad valve check reeds if no boisen get one.the swing arm & links thay take a lot of water regrease every 500 1000mi regrease steering head wheels and itmight fell new its a great bike never left me stranded can`t rember any more ask away and i will try to answer . ride hard

The American Market KDX's are premix. Both my 1993 200 and my 1998 KDX220SR were imported from the Japanese Market. Both had oil pumps and smaller carburetors (28mm). I eventually condemned these pumps and opted for pre-mix using Belray MC-1 at 40:1. If I used the MC-3 I would have mixed at 32:1. The '93 model has upsidedown forks, the '98 model has regular forks. Don't know why they switched back.

Feanor, I think the idea is to properly maintain the suspension, not wait until a seal blows and skeets all over the place. :-) If a conventional fork bike has a weeping seal, it is not going to leak upward and be easy to spot. :-)

"technology du jour"?? Production KTM's had WP USD forks back in 1985, ya know. There have also been quite a few since then. :-)

ANY fork can be sprung and valved to ride like crap or ride smoothly through any slow section.

To the original poster, good job on getting a KDX. The USD forks are better than the recent model's forks just by design, so don't worry about that. DO check the KIPS actuation. It might not hurt to check out a lot of thigns just to make sure everything is right. It IS a used bike. What the previous owner thinks or says can sometimes be different than what you see when you start disassembling and inspecting things.

Good luck with it!