Kawasaki KX200 rebuild

More things have happened...

Installed an extra mounting point on the back of the airbox for the wrong shock mudflap that I am using.

/\ Detail shot of normally obscured things looking pretty.

Head mount removal...

...Because the fuel tank hits on it.

I still need to hit the tank with the heat gun to clear the thermostat housing.

But yeah, the motor is in!

Swingarm and rear suspension all sorted too.

Airbox had to be resealed - there’s the plastic box and the rubber boot sandwiched between two thin steel plates. One of the plates has five studs sticking out of it - one has been snapped off, and was (presumably) why the previous owner had pulled it all apart.

After a lot of wondering how to seal all of the elements without making a huge mess with silastic, I realised that I only needed a good seal between the inner ring and the rubber boot - much easier. Bit of head scratching on the broken stud, then just fitted a countersunk screw. Simples.

Kawasakis of this era are notorious for crappy welding on the frame.

This ignition mount is a case in point. While it is plenty strong enough to hold the CDI box, it lets water into the steering bearings.

Easy solution was a smear of sikaflex on the inside.

Gearlever is a close fit, but clears.

Radiators are the next challenge.

The radiator on the left is from a 1988 KX250, the one on the right is from the 1990 KX125. I do not own a pair of radiators for either bike.

The older KX water path is motor - first radiator - second radiator - back to motor.

The 1990 water path splits the coolant between each radiator, and has a balance pipe between the radiators.

The KDX motor has the older set up, so it is easier to go that way.

I was juuuuusst about to buy new 88 KX250 radiators from ebay when I realised that I wasn’t certain that the RHS radiator would fit my frame. After a bit of research (asking on Facebook and having a mate ring me from his shed! ?), I discovered the 250 radiator is too long for my bike.

Glad I asked first!

Next step is to try KDX200 radiators.

And there’s the budget blown on the 1990 model...

I am justifying it by the money I have saved by not doing anything apart from going to work.

Fuel tank tidy up. I seem to be getting on top of the 20/80 rule when it comes to making old plastic fuel tanks look ok again.

As usual, I missed a bunch of photos, but this should be enough to get the idea.

First step is to scrape off the chalky outer layer.

Then wet sand with 240 grit.

They always look great when they’re wet (above), but once the surface dries out, you can see how much more work is needed...

And repeat the sanding with 600 grit...

Then 800...

And then 1200. The 1200 is the worst - while it is wet, it looks perfect and you start thinking that it is almost finished - then it dries out and you realise that there’s heaps more to do...

Even wiping it with a dry rag doesn’t help - you have to wait until the water evaporates out of the tiny scratches.

But eventually the colour is nice and even, albeit it entirely matt.

Then a bunch of fun with the heat gun to bring the gloss back to the surface.

I borrowed a decent heat gun for this task which was far more enjoyable than using my ancient, non-adjustable one. Set to 400*C, fan on the middle setting, and the task was relatively pleasant.

There are people who can do a FAR better job than this, but for a bike that is going to be ridden, this is plenty good enough for me - 20% of the effort for 80% of the outcome!

In the past, I have put in the effort to get tanks really good, but they end up looking like this after the first ride anyway.

Today’s other fuel tank challenge was to add the dent to the underside so it clears the 200 cylinder head. I did this halfway through making the outside look good, so the photos aren’t in sequence.

First I tried half filling the tank with boiling water and using the heat gun on the outside, but the water was too much of a heatsink.

Drained the water, turned the heat gun down to 320* and very carefully heated the entire area around where I needed extra clearance. Slllooooooow process, particularly because the plastic is so thick at this point - feels like 5 or 6mm.

When I first tried to reshape the tank, the outside surface was soft/semi molten, but the inside surface was still firm - all that was happening was that I was pushing the soft surface layer off the harder, cooler material underneath. So back to heating it until the entire thickness was soft.

I really needed a roughly spherical shape, but an old glass coke bottle was the best that I could manage.

Had to keep pushing the plastic down as it cooled because it wanted to return to its original shape. My shoulders are sore now!

Anyway, its not pretty but mission accomplished!

If it needs more clearance or the plastic wants to come back to its original shape over time, then I will make up a nice mandril out of bog or something.

No cigar!

It isn’t wonderfully clear, but the tank is sitting too high/forward on the frame, because the head still touches. The gap between the tank and frame should be smaller.

In an attempt to avoid modifying the tank anymore (‘cause I am sick of the smell of hot plastic and now is not the time to be going to hospital with breathing difficulties), here is the spare cylinder head after modification:

The KDX200 motor runs a thermostat, which is uncommon in dirt bikes and very uncommon back then.

So I cut the thermostat housing down as far as I dared to make more room under the tank.

Just used a hacksaw to cut it down and got the new gasket surface pretty flat by not quite square.

Then tried the flat surface on the linisher and made a right mess of it - a big step backwards!

Next was a hand file which worked great but I couldn’t quite get right until I realised that the gasket face on the water neck was not flat.

Sorted that with a piece of wet and dry on a flat surface. A bit more filing of the head and then some wet and dry on it, and the world was a happy place again.

The blind bolt holes that hold the water neck to the head are now too shallow. I will have to drill them down into the water jacket and tap the threads deeper. Then I will need to fit fibre washers under the bolt heads to stop coolant escaping out that way.

I was far more aggressive with removing the mounting point for the frame this time.

And after all that, I suspect that the tank will still need some more modification... ?