Took the DT out for it's inaugural run today as the registration has arrived.
Was wet today and off road was muddy, loved it.
The not so fun bits are, I think it's running rich as it's blubbery below 40% throttle, but open it up and she's away.
I'll drop the needle tomorrow and see if that helps with the running.
Second issue is the play in the connection between swing-arm and shock, see the video attached.
I see from the manual that there are a pair of solid bushes there and thrust washers and washer.
After having a quick look in the dark I can see the split pin is missing which wont be helping.
Swing-arm itself feels fine and I can't feel any side to side play.
I'll have a look tomorrow and probably take the swing-arm off as it needs a bit of paint anyway.
Other than that it was a blast and took me right back to riding my original DT.
Has a lot more oomph than the CT's, but not as pretty
 

Monoshock play

Great looking bike, glad you got it out for its run. I’m sure you’ll get it running right and have years of fun on it. 

Crap weather has stopped me delving into the shock bushings although I had a better look in the daylight between showers.
Looks like the previous owner has tried to remove the pivot pin and has mushroomed the end of it, so I'll need to file that in situ so the pin has a chance to pass through.
I've sprayed it with some penetrating oil while I wait for a chance to have a go at it.
I did drop the needle today and nearly lost the needle clip as it sprang off .
Luckily the power of the magnet saved the day and picked it up off my driveway after a few passes. Lesson learned, I took it inside to put it back on.
Took it up the road for a test and it's really good.
Got my GoPro out and recorded a second run,pick up really well and revs freely, see video link.
DT175MX Dropped the needle

Sounds like it's running very well! I have to say, I don't know if I could ever get used to driving on the left side of the road, of course you might say the same thing about driving on the right side of the road here in America.

Beautiful bike, congratulations!

I think the slop your seeing between the swing arm and mono shock is due to slop between swing arm and frame, either due to a missing shim or worn bushings or both imo. 

Martin, you’re right there is also play in the swing arm bushes.
The swing arm to shock pivot (let’s call it the upper) as I said has a lot of play, so I’ll do both sets.
Managed to file the end of the upper pivot pin and got it to move about 1mm, the lower pivot rotates but is tight as, so it’s going to be a steady approach and hope the penetrating oil works its magic.
I’m in no rush and I have a few other rides if the weather picks up 

Frame painted and looking great.
Swingarm powder coated and new bushes fitted to it and the monoshock, no more play.
Too cold in the shed so it's inside for a bit of assembly.
I blame Greatuncleal as I've seen one of his RDs in the kitchen 
 

Great job, Pete  , although those leaves in the garden should have been cleared up yonks ago! 

Don't you think I've been really generous in the amount of space that I've left on the kitchen table for Gr8auntiepat?! 

Bike being worked on is a 1975 UK RD200B and the tank on the table is from a 1975 UK RD250B.

  

Unbelievable, wow the wives here in the colonies would have left me had I expanded beyond the garage!

I know my wife is very lenient I’ve got 5 vintage coke machines 4 vintage gas pumps and a Mercury neon dealership sign in my house but she would raise Cain if I worked on my Yamaha in the kitchen no more home cooked meals for me. 
   Would probably put Yamalube in my salad