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Airhead?
Posted: 01:31 am Oct 16 2011
by FRECNDY
Has anybody done a hybrid with an aircooled KDX200 motor? Seems like it might be a plan if you were pursuing absolute minimum weight, eliminating the need for radiators, coolant, armor, shrouds, etc.
I could see the pipe being a problem, since it points out to the left rather than coming out the front of the cylinder and goes high on the right. Could have issues clearing the frame. Might need to build something custom to make it work.
Do RB mods apply to air cooled with PWK? Do aircooled motors have the same KIPS reliability issues as water-cooled Es?
Any other thoughts?
Posted: 11:02 am Oct 17 2011
by fuzzy
RB mods would still apply. I'd definitely stick with the last gen AC motor...87/88? That is a nickel bore, and I believe identical KIPS design to the E.
Posted: 08:44 pm Oct 17 2011
by FRECNDY
I figured waiting for a donor '88 with the Keihin 35mm PWK on it from the factory would be the way to go. Good info to not get an earlier one and try to swap on the Keihin.
I need a larger garage. The YZ and the Husky are already a little much in the tiny space I have. Miss my old house, where I had a two post lift for the cages, etc.
Posted: 12:42 am Dec 25 2011
by jgas1
Oh boy, oh boy, whoooopeeee, halleyberryallujah! Crazy people who think like I do! Only problem is that I think I have all the creative genius ya'll have, but lack the brains and exprience to actually make it happen. Oh, well... lack of brains never stopped me from trying and failing before. Why start now?
I raced a KDX (89), from 1990-1994, when I bought a brand new left over 91 KX 500. See what I mean bout lack of brains? What little I had quickly got bashed hard and often from the 500. But I shure had fun between bashes. Went from a KDX 200 to a KX 500 in one day. It still hurts thinking about it. But I still grin thinking about it.
Now I'm old and fat and brain damaged, remembering the glory days, and I want to build another KDX. A non-racing buddy of mine has been sitting on a decent looking 83 KDX 250 for 8 years. He wouldn't fix it, wouldn't sell it. He finally sold it to me. It needs more than I thought. to get it working. I would probably spend way more than its worth restoring it. So my brain damaged noodle went to work. Always a dangerous thing.
I think I can: Transplant an 87-88 200 motor. Cut up the frame and weld on a later model section so I can use modern forks. Or, I could much more easily use conventional forks of some type.
Cut out a large section of the rear shock area at the top of the frame and fabricate in mounts for a late model KTM laid down no linkage shock. The 83 has no modern type bottom linkage, (don't know what that arm set up is callled, was it Uni-Trak)? so it is already set up for the bottom shock mount on top of the swingarm. Don't know if I would switch to a disc brake rear wheel or stick with the drum. Probably have to go disc as I'm a brake dragger from an old injury. Worry about that if everything else works out.
If it all works like I have it in my head, it would handle well, probably not as well as a true modern bike, but much better than an early 80s. It would have more frame flex, old school frame geometry, old school ergos, and who knows how it would all work together?
One small problem. I don't really know how to weld. I bought a welder and buillt a small bike trailer to teach myself. So far it hasn't fallen apart, but it sure has some ugly welds. What the heck. I just won't let anyone else ride the bike but me. If the frame breaks in half with me on it, I'll only have myself to blame. It'll be fun while it lasts.
On the plus, if it holds together, it would have fairly modern suspension, be simple and light, easy to work on, look retro, the 87-88 motors were pretty quick and reliable, and I remember the carbs were easy to jet and they ran clean and had good response for the day.
Best of all, no one else would have one. Of course, they probably wouldn't want one either.
Anyone know where I can find an 87-88 KDX, complete bike or just a motor? And a welding manual for beginners?
Posted: 02:55 am Dec 25 2011
by FRECNDY
That is just a bad idea. Putting an old motor that is proven, popular and developed into a complete modern chassis to make better use of its characteristics makes sense. Putting that same motor in an even older and more outdated chassis is a sign of having been dropped on your head too many times.
If you can get the 250 motor running, swapping it into a modern chassis (pick a 1998-ish or newer two-stroke chassis, would be my suggestion) might be cool. If you're going to go looking for a KDX 200 or 220 motor, part out the 250 on fleabay (use keywords to get vintage racers to look at it) and use whatever money you can salvage to find a modern 125 with a blown motor to put the 200 motor in.
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Regarding my airhead question asked above, I think the pipe being off to one side would point toward using a 250F chassis where the down tube is typically a single tube to a lower point, so that the two pipes can go around it.
But the fact people have found a CR250 pipe actually works will with an E motor points to going with liquid and using a CR250 pipe in a CR125 chassis. I think that's probably the easiest KDX hybrid going.
Posted: 10:44 am Dec 25 2011
by SS109
Posted: 01:32 pm Dec 25 2011
by FRECNDY
Thanks for posting that. I read it back when there were only four parts up.
Just read parts 5-9. I HATE the carb boot and pipe. Both are absolutely horrible. Hacks like that are what people assume is going on when they talk trash about just the idea of an engine swap. Still like the idea of the project, though.
Posted: 11:05 pm Dec 25 2011
by dfeckel
About the KIPS, the '86-'88 air cooled motors do have them, but it's a different set up than the E. They have two smaller sub valves and no main center valve.
airhead
Posted: 11:51 pm Dec 25 2011
by canamfan
sounds like you need a ATK aircooled single shock bike not kdx but it sounds like what your wanting. I've got a 90 250 model I'm waiting on a cylinder to come back on, so I can put it together, I've never ridden it, but am interested in how it handles.
Posted: 01:09 am Dec 26 2011
by FRECNDY
Actually, since I saw multiple people post that they randomly tried a CR250 pipe they happened to have when putting an E in a CR125 chassis, and were surprised how well it worked, I'm thinking that's likely the best option for a KDX swap, unless you like the idea of building custom pipes for fun.
Posted: 08:34 am Dec 26 2011
by frankenschwinn
The 02 kx chassis is super easy with very little pipe mode needed.
Posted: 11:47 am Dec 26 2011
by FRECNDY
Read the CR threads. It looks even easier than a KX.
Posted: 08:44 pm Jan 05 2012
by THill
FRECNDY wrote:Thanks for posting that. I read it back when there were only four parts up.
Just read parts 5-9. I HATE the carb boot and pipe. Both are absolutely horrible. Hacks like that are what people assume is going on when they talk trash about just the idea of an engine swap. Still like the idea of the project, though.
Man I agree,that pipe and air intake look awful....BUT !!
One little project i've had in the back of my mind for awhile has been putting one of the old rotary valve F7 175 Kaw motor in one of the last year of the air cooled KDX or KX...I had a 72 and 75 F7 and those old motors were tough !....Something that would be abit different forsure and i'd say fun to beat around on the trails with too...