I have finally found a pretty original DT1 from 1969.
It's got a 68 paint job ( white ) but I'm not fussed about that. All the parts that matter are there undamaged and corrosion free. I was quite amazed how much lighter it feels than my RT1B.  The headstock is different too.
frame numbers on  the opposite side than normal and when you sit on it it feels racey compared to the other bikes i have. I think there could be something not right with the front fork action. There's way to much dynamic sag and i can hear the spring on the left leg touching the stanchion when it's compressed.
The paint quality is good but his prep work and attention to detail wasn't A1. Everything works. It starts but sounds like the piston wants to exit the cylinder. Like the rings could be stuck back.
The PO was honest and a great lad who had 22 bikes In various sheds and his house.  He had sold 10 bikes and still had the 22 left. He just does them up and puts them away. The DT1  has been stood for three years and never used . I finally have a true landmark motorcycle and I know the people who developed it.
When I can post a picture normally I will.
Dave

Does anyone know if there's anyone out there who replicates the fiber webbing type seat strap that prevents  the DT1 seat from flopping all the way over? I have the mounts and the strap but it's rotted away on the seat side.
Dave.

The 70/71 Kawasaki F5 bighorn uses an identical design strap on their seat .
It is 25 mm odd longer than the Yamaha unit , which is actually a wee bit better ,
as it allows the seat to remain open with the bike on the side stand .
They don't come up for sale often , but more frequently than the Yamaha part .
There was a replica produced some years back , but the company retailing them  ,
is no longer around .
 

Great stuff thanks. Fortunately I know someone who does lots of Kawasaki and currently has a couple of KEs on the go. 

There's a Kawasaki nos strap on e-bay. He wants $85.00 for it. As for the original material, i can not find anyone who replicates it but you can buy military or olive green color strap on e-bay and Amazon. I bought some off Amazon to make 1 or 2 and see how they turn out.  A member on the 68 DT1 facebook club said he just went down and bought a green dog leash at his local tractor supply store and sewed his ends on it.  I only have 1 end so i have to make it too!  I do have a good strap on my 70 DT1 so i can get it close and have it sewed like the stock strap. 

Thanks Skydancer46

When i get them done, i will let you know how they turned out and post a picture.

I'm still at work and i must have read the workshop manual three or four times.
Jobs list is as follows :

Re spoke the front and rear wheels.
Re chrome both rims as corrosion is starting to blister up a little in places.
Re finish both hubs.
Paint the tank as there are rust patches on the left hand side. Also,the finish isn't right.
Change the petrol tap and the hose.
Replace the Jubilee clip that's on the carb inlet hose with the proper Yamaha item.
Inspect the crank and do the gearbox updates stated in the service bulletin
Replace the seals and bearings .
Re bore the cylinder and if necessary,rebuild the crank.
Vapour blast the cases,barrel and head.

The bike had been left in a damp shed for three years after it's restoration and that list is pretty much the result of English winters and summers for that matter. The bike hasn't been ridden or started regularly . The top end is really noisy. It has it's original crank seals in and the motor hasn't been apart so it will be interesting to see what's going on up top.

My first bike was a '69 (my avatar is me on it). Loved the bike, had to sell on when I crossed the country in '72 (on a '70 Kawasaki H1!).

I picked up a reproduction seat strap a few years back for an on-going '68 rebuild. Don't recall the seller. This sounds like a project for KDI to me. I think I'll drop him a line. If others did as also he might be encouraged to try it. I'll bet he could sell several.

FWIW regarding re-chroming your rims:

I had mine re-chromed for the '68. I got a very good job done (to my eye anyway). As I am "restoring", I felt that the Takasago brand lettering needed to be seen and present. I was told by the chromer that in the process of cleaning up the rim and then the multiple coatings, etc., that the lettering would be lost.
I did not want that.
I paid extra to have all that small print more deeply engraved, so that when the rims were finally chromed they are readily seen. This was a big expense for me. The whole process came to over $1100. 

A couple of members here pointed me to a source on eBay that was providing decent chrome rims (out of Italy I think) that were just around $90-100. 

Might be worth it to check that out before deciding to have them done is all I'm suggesting. I've gotten far more money into this project than it is worth, nor will I ever get should I sell.

NHSTEVE do you have a link or name of the company for the rims on e-bay. I was going to have my DT400 and DT2 re-chromed but if the e-bay rims are quality I'd go that route and maybe some day have the originals re-chromed. Thanks!