Here is a beauty on ebay

http://www.ebay.com.au/itm/1978-Yamaha-DT400-DT-400-totally-restored-when-big-two-strokes-ruled-the-earth-/111075547205?pt=AU_Motorcycles&hash=item19dc9e5845&_uhb=1

I have a 1981 XT250 which i restored as new - only done 5000km since new - its the model with red tank and sidecovers, and white guards, new everything just about, new plastics, spokes, tyres, seat cover. Bolts replated, no expense spared, looks almost new and runs beautifully and starts in two or three kicks every time. It was a one owner bike when i bought it and had hardly been used. Cannot seem to work out how to add photos here, so if anyone is interested i will send photos and you can make me a sensible offer. It is currently registered in Qld and i use it every couple of weeks to go to the shops or visit locally. Real trip down memory lane, its amazing how many people stop me and say they had one of them back in the good old days. 

My 1978 KX125 A4 is on ebay - as anyone from the era will remember, these were and still probably are, perhaps the rarest and most exotic of the early evo KX's  - very light and very fast. with lots of trick little touches only found on the works bikes of the times. Knowing most 125's there will be very few of these left alive. I have only ever seen one other.  PM me with any questions.

Good condition Ohlins shock to fit the 1989 onwards KX500 and the 1989 KX250 - it may fit later KX250's past 1989 as I think the linkage was the same for a few years - will send photo to anyone who is interested - price is $500 plus postage

The swept back handlebar clamps are correct, the 1978 KX125 had straight upright mounts, they may have got the photos wrong in the manuals or possibly the preproduction prototype which they use for the photos for the manual may have had the 125 clamps - who knows. Also note on the preproduction KX250A4's which were given to the press for magazine testing in advance of the actual production bike launch had fins which ran all round the base of the forks below the axle, but the production bike had only token fins on the front section of the forks below the axle. They are great bikes, attention to detail which was comparable to that only seen on factory bikes at that time.

Taken from 1981 KLX250 - apparently can be used on several other bikes - PM for info

A big thanks to Lawrie and Doug and the Toowoomba Club and everyone who helped. It was a great day, a true old school enduro and the optional downhill with the F....... Hard warning on the arrow - lived up to the sign.  Great job and a good bunch of blokes.  Looking forward to the next one.

The KIPS was first used on the production KX125 and KX250 in 1985 , it was then introduced onto the 500 in 1986.

With regard to the works bikes, the 1984 SR125 had the KIPS system from the beginning of the 84 season, which Jeff Ward used to win Kawasaki their first 125 National Championship.  Then in late 1984 Kawasaki air freighted works power valve equipped sand cast 250cc engines in for the USA factory team and these were fitted to the 1984 works bikes for evaluation until the full 1985 KIPS equipped works bikes arrived in early 1985. The 1984 works 250 was a centre port already but with no power valve, (production was sideport) so the when the first works power valve engines arrived they  fitted the 1984 works frame with some mods. 

The first works SR500 to use a power valve was the bike used by Georges Jobe in the 1985 GP's , it used a special sand cast engine with a sandcast  cylinder with a power valve. likewise the American factory 500's. By 1986 this was on the production KX500.

Firko - use the KX A5 frame - it has excellent geometery and adding the bigger engine just makes it feel even more planted. I do not know about using a KLX frame but would guess it would fit.  Rusty and Simon Healy have proved the concept with their success on them. The KDX frame is longer and does not have MX geometery, feels long on a track. Plus the KDX is a big bike when you sit on it, compared to the A5 which feels small. Although the fat thick KDX seat is a real pleasure. The engine almost drops into the A5 frame, you need revised engine mounting plates, and you have to machine down the steel collars in the rear engine mount where the swingarm bolt goes through , as the A5 has a smaller gap between the two swingarm inner pivots than the Unitrak which is larger.  The 1980 KDX400A2 uses KX420 cases - these are an easier fit than the 1979 KDX400A1 which uses a bracket to connect the motor to the swingarm. 

This is for KDX fans.  There is some interesting history on the KDX400 and its great engine. The KDX400 has to be one of the most under rated bikes of the Evo period. All tests of the period were lavish in their praise of it. It was designed in the USA by Americans and was built in the new Kawasaki factory in Lincoln, Nebraska. The engine was shipped in complete from Japan, as was the swingarm and wheels etc but the tank and plastics were sourced in the USA - which probably explains why the KDX400 plastics did not wear well compared to other Kaw plastic of the same era. It had stump pulling power and could reach almost a  hundred miles an hour tapped out.

Brad Lackey joined Kawasaki in late 1978.  In his first months with Kawasaki, Brad initially practiced on a twinshock open class works bike which looked like a KX250A5 from a distance, however in common with most works bikes it was actually nothing like an A5, but was powered by a 390cc modified KDX400 engine. This was while waiting for his new works Unitrak to be built and flown in to the USA.

The KDX400 powered twinshock works bike was successful and a second one was used by Gaylon Mosier in the USA. If you look at Brads book - Motocross - techniques training and tactics - there are quite a few photos of him riding it. When the works Unitrak arrived Brad parked the twinshock 390 and it was purchased by Kawasaki UK and shipped to the UK for use by future 3 time world champ Dave Thorpe.  Dave Thorpe used it for several months in the UK and did very well. He only stopped riding it when his own works Unitrak arrived in April or May 1979. Both the Mosier 390 and the Lackey/Thorpe 390 still survive to this day. To make the engine more MX orientated Kawasaki changed the pipe, jetting, ported the cylinder and changed the gearing and once installed in a more MX orientated frame and suspension it did the business.

So the humble KDX400 has some history.

You can run the 17.5 inch shocks with no problems, however you must fit longer forks to restore the geometery. If you can find a set of 1980/81 KX250 forks they slot straight in with no mods (same front wheel, axle etc) and have an extra inch and a half of travel. You can also use KX420 forks, but the spring rate in them is a bit stiffer, depends on your weight.  Alternatively you can always upgrade to a 43mm front end off a completely different bike.  I noticed that my A5 corners better with the original forks and shocks than the longer ones, slightly lower to the ground. However when I have the 43mm forks and 17.5 Fox shox on, the ride is better through the rough stuff.  Hope that helps.

KLX Update - thanks for all the info over the past few months, I have finally fitted the new Wiseco 262 piston mated to a specially made up 1.5 inch diameter pipe with a Supertrapp muffler, still using the standard carb and cam . I fitted new valves, and cleaned up the ports. The bike now runs really well, pulls strong and smooth all the way through the range - feels like a different bike. Handles, turns and has power to boot.   Can anyone advise what difference a larger carb or the Megacycle cam will make and also does anyone have any recommendations with regards to optional rear shocks?  Cheers.

I am looking for a original plastic tank for a monoshock TY250R 1984 onwards,  the original tin tank on my S model has seen better days. The TY250S had a tin tank, while the following TY250R models had plastic tanks.  Any help or leads as to finding one would be appreciated. Thanks all.

Thanks Tim, just bought mine, looking forward to restoring it. In very good shape for its age. Will post some photos soon.

Thanks Tim just what I wanted. Cheers