Posts
14
Joined
1/21/2016
Location
NZ
Edited Date/Time
1/23/2016 1:17am
Hi - thought I'd share my long term project. It started out as a restoration on a 1987 KDX200 but then took a different turn. I rebuilt the motor (new bearings, seals, Nikasil, piston, blasted the cases) then the motor sat around under my bench for years. I realised that it was the engine I loved (back in the day) rather than the chassis - Power Valve, 6 speed, compact. I started thinking about the concept of a low tech trail bike that would keep with modern day machines. I started collecting bits to build it up.
86 KX125 frame and swing arm, rear wheel (first of the modern day linkage, rear disc but with single downtube frame)
87 KX piggy back shock, YZ titanium spring.
89 KX subframe (to take the 89 side panels, airbox, seat and rear guard)
98 RM125 Showa conventional 49mm forks, Gold Valves, revalved.
YZ Ti footpags.
Handmade tank.
I finished it off with FMF pipe and PWK Air Striker carb. It's still a work in progress but runs pretty well now. It's light like a 125, handles nice (turns well and doesn't head shake). The motor is raw by modern standards but pulls very hard right from idle, Definitely a pipey engine but it gets the power down well.
It's a never ending project
Always something to tweak. My next step might be the same engine in an 89 KX125 frame.
86 KX125 frame and swing arm, rear wheel (first of the modern day linkage, rear disc but with single downtube frame)
87 KX piggy back shock, YZ titanium spring.
89 KX subframe (to take the 89 side panels, airbox, seat and rear guard)
98 RM125 Showa conventional 49mm forks, Gold Valves, revalved.
YZ Ti footpags.
Handmade tank.
I finished it off with FMF pipe and PWK Air Striker carb. It's still a work in progress but runs pretty well now. It's light like a 125, handles nice (turns well and doesn't head shake). The motor is raw by modern standards but pulls very hard right from idle, Definitely a pipey engine but it gets the power down well.
It's a never ending project
Always something to tweak. My next step might be the same engine in an 89 KX125 frame.
I enduro a modern KTM 200 with a toned-down motor that'll lug 3rd at walking pace and pick up cleanly.
Excels on the technical routes, and doesn't beat me up too much either.
Smooth linear power, and makes sure it all gets to the ground.
Your bike sounds like a very similar recipe.
Very few people will understand it till they ride it, but out in the real world it's a fantastic weapon.
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I've always wanted to put a air cooled YZ 250/open motor in a 06 or new YZ chassis as I think it would be a fun light bike with out the head ache of liquid cooling.
the 86 handles pretty good for its age! The geometry is almost identical to the first gen KX250F (same steering angle, trail, triple offset, wheelbase etc). With modern suspension it should be in the ball park.
Is that a 125 or 200 pipe? I want one now. I'll probably have to buy a pretty made ktm200
The motor going in was the easy part. The cases fitted into the swing arm gap fine, same size pivot bolt. Just made up ally triangle mount plates to hold the front then got the steel mounts on the cradle underneath moved about 1 cm. Done.
The only major fabrication was making up the mounts to hold the subframe and the back of the tank onto the frame. The rest sort of bolted up.
I used KXF250 triples (the right offset) with a new machined stem and had sleeves made to hold the forks. Shortened the 87 shock 10mm to fit. The tank was a necessity because of the new subframe and the way it mounted. None of the air cooled tanks fitted anywhere close. I made it up from cardboard then got a local fabricator to cut it out of ally sheet and put it together. The pipe is a Gold Series 200 one (86-88) with a later KDX E series silencer.
I've been out riding it more lately after neglecting it in favour of a newer bike. I forgot just how good it handles, and how light it is, so I'm back on it now, and selling the other. It has all the power I need for the tight single track sand riding where I live.
The air cooled cylinder looks cool with a power valve.I think the only other air cooled power valve motor I've ever seen was a Factory OW250 Yamaha
The 89 shares broad compatibility with KDX E series and all KX500s to date. So when it comes to things like rebuilding the linkage it's easy to get aftermarket bearings and seals. There's nothing aftermarket for the 86.
The swing arm is a more modern set up with the sliding spacer blocks. Also if I can find a nice KX5 shock (like an Ohlins or WP) it will go straight in.
I'm hoping also that the 89 frame might have a bit more space around the side tubes and shock to accommodate the carb that comes back a bit further than on the 125. At the moment trying to put the carb boot back on with its clamp in place is a major manoeuvre.
the KTM fork guards.
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