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KDX200SR of green


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Not much progress at the moment, waiting on some transmission bearings and case sealant to arrive but other things are under way.

I sourced some of these things



Which will let me use the bigger one of these.


Stock on the SR is a 28mm carby, dirt 200 is 35mm.

The SR has oil injection through a port in the inlet rubber, the new inlet I will use doesn't have this as the 35mm carbs are used on premix only bikes.


So I'll drill an unused boss on the carb and feed it in through there.




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Yeah, I would assume so. More air = more fuel combined with stock oil flow would make a weaker fuel oil mix.

Was thinking I would run it premix to start with and do some measurements on the oil injection pump. It has some adjustment in it so will see if I can get more flow, it may only adjust when it goes full open but we'll have a look anyway.

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Crankcase all back together. I found it is missing a washer on the clutch release mechanism, I can't see how it would negatively impact it other than reducing its throw and it has been running for who knows how long without it but I'll order a new one as its a 5 min job to install.


I'm still waiting on an output shaft collar to arrive and need to order a new piston but in the meantime I can move on to cleaning up the cylinder and the powervalves.



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I have cleaned up the cylinder and power valves, there was a lot of spooge but a soak in some petrol made it easy.

Valves back in now and operating smoothly.


Here are the valves in their closed state which is below 4000ish rpm, you can see the centre valve at the top of the port and one of the side valves to the left.


Open state, you can now see the extra exhaust ports that the side valve uncovers.


From the top you can see the main exhaust port and the extra two on either side the power valves control.


Nothing left to do engine wise at the moment so I gave the frame a clean so that it's ready.



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For only 200cc it can be a bit of a handful. Power comes on very quickly once the revs are up, wants to lift the front all the time so need to get up over the bars but it still has decent low down power so can be ridden civilly.

I need to clean up the pilot jet circuit though, feels a bit 4 stroky just off idle. Ideally I'd bung on the replacement carb and tune that but I am still sussing the oiling system. CBF running premix due to hassle and 40:1 at low road rpms will poo everything up, the injection pump runs about 90:1 at idle.

I remembered that there is a 250cc version that runs a 33mm carb and oil injection so I picked up the pump from one of them. I suspect the pumps might be identical and are just geared differently, if that is the case I should have the option of swapping gears or boring the pump and making a new piston for it.



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The SR version was the only model designed to be used on road, comes with an extra charging coil and all the lights, speedo etc, regular KDX will just be a headlight and taillight and premix.
You can put most of the gear on a non-SR easily enough, the hard part I guess would be compliance and what kind of checks there are that would stop an off road vehicle from being vinned.

Early 90's RMX250 is another that had a street legal version, they come in a tasty yellow colour.

This one has been listed for a while due to price, it's an F1 version which from what I have seen is just an SR with right way up forks that was for the Oz market.


There isn't many of these bikes in NZ but they do pop up.
Lots on Yahoo Auctions :grin:



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