1987 KDX200

[benroloff]

Well the FZ I got from ex119x is officially gone. And as happy as I am for him to have passed that bike to me, it’s leaving opened a door to a new-to-me bike… a 1987 KDX200. Kinda funny that it’s the same year as the FZ lol.
Anyway, I picked up this gem earlier tonight from a local guy. It’s 90% complete I’d say, and it fired right up with just a touch of fiddling.
Outlook for this one is mostly just riding, but i figure I’ll post any mods or upgrades I do for the dirt folks on here anyways!

Smoky smoky…. (My roommates 1986 xl600r in the garage, now that’s a sweet bike)


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[Hurco550]

So Cooool ! I have A TON of love for the air cooled KDX's. I owned one for a minute, and while it turned out to be a bit more of a dud than I wanted (P.O. was maybe a little dishonest about the condition of some things) I still keep a constant look out for an 86-88.

@CCRider has one that he's let me throw a leg over a few times, and thats where the bug for them really bit me.

And another close buddy of mine @Chuck78 is the DTT resident expert on all things KDX. Ive ended up needing stitches following him around on some gnarly single track. He's a wealth of knowledge on them.

 

[benroloff]

Glad to see there’s some love for the kdx around here! Maybe this’ll stir some activity up on here for these bikes
I was a little apprehensive initially to the air cooled aspect, I really wanted a water pumper kdx, but seems like these c series bikes are really tough and a pretty good chassis too for going on 40 years old. Interesting too that they share pistons with the water pumpers. Someday I’d like to do a rear disk swap, and either re-epoxy the flywheel magnets for peace of mind or upgrade to a newer stator/flywheel.
I am in the market for a headlight for it too, so if anyone has a kdx headlight(doesn’t need to be from a c series), or a acerbis Elba headlight, or really just any old school enduro style headlight, let me know as I’ll probably be interested


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[Chuck78]

Very nice score on the 86-88 KDX!
Those things are gems, truly the best small/medium bore vintage air cooled woods bikes of all time... The '86 Yamaha IT comes close, and the only thing surpassing it in air cooled enduro bikes is the 2-year-only 1991-ish Yamaha WR500 2-stroke...

I'd highly advise you fully epoxy encase the stock flywheel's rotor magnets in proper epoxy before firing it up again. My buddy made the same mistake, and his self destructed. You can re-clock the E-series and H-Series water cooled KDX stator plates to run those with the matching flywheel rotors, but you can also just buy a Powerdynamo ignition direct from vape.eu or whoever their US distributor is. My buddy ended up meeting up with the US distributor at AMA Vintage Motorcycle Days last year and picked up a new ignition system from them. They use fixed stator positioning and use no key on the flywheel, so that they flywheel is the timing adjustment.

There's a really killer build on KDXRider.net of an 86-88, with rear disc, modern fork swap, etc etc etc....

They are truly a masterpiece, being a lot lighter weight due to being air cooled, having an awesome linkage design that's up out of the way and has grease fittings, air cooled electrofusion plated cylinder with power valves! That's a very advanced feature not found on really any other air cooled bike...
If the shock starts leaking or shows signs of leakage, send it to Works Enduro Rider (WER Products) or RaceTech, for a full rebuild and most importantly a hard anodizing treatment. All the 1980's monoshock bikes use aluminum cylinders, but they will wear excessively especially if they start leaking out all their oil... you want to have them hard anodized to extend their lifespan to that of modern shocks. You can otherwise get replacement KYB sealheads from Racetech etc. The remote reservoir hoses will have to be made up from fittings if they go bad.

Awesome awesome bikes, congrats on the score!


Where are you from, by the way? Anywhere in the Eastern US? We ride Southern and Eastern Ohio, Southeastern Kentucky, West Virginia, Western Virginia, etc pretty regularly, some western PA, East TN, Western NC once in a while as well. There's so much good dirt (AND STREET!) riding to be had in those mountainous areas...
Enjoy it!

 

[benroloff]

Do you have any more info on actually encasing those magnets? That was on my list to do before I even picked it up, but most of the info out there about it just says to do it, not actually how. I assume I’ll only be able to fill the voids between the magnets without causing interference elsewhere, and it doesn’t seem like that’s really do much. I’ve also heard marine grade epoxy is best for that?
It will definitely need fork seals and a shock rebuild at some point. I know I can handle the forks, but I really have to send the shock off to someone like wet or racetech right? If I could do it myself to at least get me by a couple years without spending a ton of money(i.e. my rent and tuition money) that would be nice lol.
Thanks for all the encouragement and advice! I’m really excited for this bike. When I first looked at it I wasn’t 100% sure I wanted an air cooled one, but after I did a little research I knew I had to have it. I’ll have to find that build on kdxrider. I can’t believe I haven’t seen it yet, I’ve been looking for all the info I can, and there aren’t a lot of c series builds out there.
I live in Duluth, Minnesota. About as far north as you can get around here while still being in a decent sized town. Someday I’ll have to make a trip down your direction, I’d love to ride out in the mountains. Though there is some good terrain around here and a lot of opportunity for adventure!


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[benroloff]

Popped the pipe off tonight to see what I could see on the cylinder. From what I could see it’s pretty good, however there is one vertical score mark that was enough to get my attention. It doesn’t look like it’s through the nikasil, but still concerning. Currently, considering the compression and how well the engine starts and runs, I’m ok with leaving it, at least for this summer until I can afford a re-plate next summer.
That said, any recommendations for good shops for a re-plate? I want it done right, no resleeve, just wondering if anyone’s had any particularly good experiences anywhere


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[benroloff]

PSA for those living in minnesota, with a couple of extra forms you can get any “off highway motorcycle” legally registered with street legal plates with very little extra work. I went down to the registrars office yesterday and did it in about 20 minutes, no inspection. You need to sign a form saying you have updated all of the necessary equipment to be road legal of course, but no inspection. Very easy, very cheap

Took it for its first road legal ride last night with my roommate and his 86 XL600R. The kdx is almost exactly as fast as the 600 surprisingly, but about 100lbs lighter

 

[Rider52]

That is great!

 

[benroloff]

Some questions for those of you out there with more jetting/two stroke experience than me: when this bike gets warm, when coming down off a rev, the idle sits a few hundred rpm high for a few seconds then falls back to normal. It’s not really a rev hang as it can be revved up and come down at a normal rate, but then it just sits a little high after that. I’ve checked for air leaks, and played with jetting and needle positions a little, but no avail yet. Wondering if anyone here has seen this before? Maybe it’s not abnormal and I’m just overthinking it a bit?


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[Chuck78]

Hey how's your KDX doing these days? Hopefully you've epoxy that flywheel to keep the magnets from freeing themselves...
Your air screwer pilot jetting seemed a little bit off from your last description. But the first thing I would recommend doing on an old bike like that is rig up a pressure testing setup with a compression plug in the exhaust port and some plumbing fittings in place of the carburetor so that you can pressurize it up to about 5 PSI or draw it into a vacuum, with a tee so that you can have a Schrader valve and a gauge hooked up. 5 PSI for 5 or 10 minutes with minimal leak down is plenty good from what I understand. Using soapy bubbles to spray down the crank seal on the left side, as well as the base gasket surface and head gasket surface, will help you find any air leaks. Air leaks on a two-stroke are very critical since the crankcase crankshaft area is part of the intake tract, and completely separate from the clutch case and gearbox which are splash lubricated in the gearbox oil bath.

 

[benroloff]

Chuck I’m not proud to admit that I have not epoxied those magnets… although I have removed the flywheel and inspected, only to find it in remarkable condition. I do plan to do them before riding season rolls around this spring, but I have good reason to believe this was a pretty low hour original engine before my ownership.

Other than that, I’ve done little but ride the bike. I installed a pretty period correct answer racing can on it, dialed in the tuning a bit, and that’s about it. I restored the plastics last spring, and I’d like to respray the frame in the original silver color in the next year or so. I’ve been kicking myself for passing on a DG expansion chamber a few weeks ago, so if anyone has a DG,FMF, or whatever else lying around for a C series let me know! I have the idle creep taken care of, but I’d still like to do a full rebuild with crank seals one of these years.

Here’s some pics of a couple of adventures the bike went on this summer. It’s a great trail rig for the northern MN woods, and I think I’ll hang on to it for a while. I may even have a KX250 USD front end set aside for it in the garage…

 

[Luugo86]

Chuck I’m not proud to admit that I have not epoxied those magnets… although I have removed the flywheel and inspected, only to find it in remarkable condition. I do plan to do them before riding season rolls around this spring, but I have good reason to believe this was a pretty low hour original engine before my ownership.

Other than that, I’ve done little but ride the bike. I installed a pretty period correct answer racing can on it, dialed in the tuning a bit, and that’s about it. I restored the plastics last spring, and I’d like to respray the frame in the original silver color in the next year or so. I’ve been kicking myself for passing on a DG expansion chamber a few weeks ago, so if anyone has a DG,FMF, or whatever else lying around for a C series let me know! I have the idle creep taken care of, but I’d still like to do a full rebuild with crank seals one of these years.

Here’s some pics of a couple of adventures the bike went on this summer. It’s a great trail rig for the northern MN woods, and I think I’ll hang on to it for a while. I may even have a KX250 USD front end set aside for it in the garage…

Heck ya man