DT1 flat track project

I bead blasted the hubs and then waxed them with Meguiar's Deep Crystal carnauba wax. The bearings are All Balls Racing.


I bought new rims from MikesXS. I got a 2.15x19 (part #34-2019) for the front and a 2.15x18 (part #34-1902) for the rear. At about $160 for the pair they are a great deal.

They look excellent.

The only thing I don't care for about them is that the markings are stamped on the outside, but not a big deal.

I loose laced the rims, using MikesXS standard spoke set (part #19-0051) on the front.

For the rear I used an OEM Yamaha spoke set (part 322-25304-00). The SC500 hub is wider than an XS650 hub the rims are sold for, but no issues at all with spoke hole angles.

The tires I'm using are Duro HF308, which is a clone of the old Pirelli MT53. I got a 3.50-19 for the front and a 4.00-18 rear for less than $140 for the pair shipped. They make a 4.00-19 HF308, but it is a 6 ply, while these are both 4 ply (although the Duro website shows the 4.00-18 as a 6 ply). I think the 6 ply would be too stiff to work as well. If I ever decide to do an SR/TT500 flat track bike I'll use a modern flat track tire, but I think these should work fine for this bike.

Old looks, but new tires, this is the date code of the front showing it was made in the 40th week of 2013.

Here is the 3.50-19 HF308 with an original 3.00-18 MT53 to show how close they look.

For the rear sprocket I bought a new-old-stock C.T. Alloy 'blackloy'.

The gearing is just a guess until the bike is raced, but I think a 44 tooth is a good starting point. My stock '73 DT3 had 13/44 originally, which I changed to 14/44 for better street use.

The SOK rear brake shoes are from ebay seller Benjamin Shop.
Now I've got to true the wheels, mount the tires, and polish the rear brake plate.


DT1 flat track project

The frame for this bike is a '68 DT1, but I'm using a '72/'73 DT2/3 reed valve engine. Here is the reed cage with stock reeds.

Here are the stock reeds and the Boyesen dual stage power reeds.

The new reeds installed in the stock cage.

Pretty much the engine is done now except for the ignition and carburetor. I've got a stock flange mount Mikuni round slide 26mm carb, but might go with a new 28mm spigot mount. A new VM28 is about $95, and when you figure in the time and money to do a proper rebuild on the stock carb, I might be better off just starting off with a brand new one. Here is a Mikuni m-vm28-200k adapter.

This would let me use a new spigot mount VM if I decide to go that route.


DT1 flat track project

The piston I'm using is Wiseco part # 234M07100.

Here it is with a stock piston for comparison. I'd read the Wiseco pistons were heavier than stock and was curious what the weight difference was between the two so weighed them on my digital scale. The Wiseco is a brand new 71.00mm piston and the stock one is a used 70.00mm, so not a direct comparison, but the stock piston (with pin, rings, and clips) weighed 300 grams, and the Wiseco (also with pin, rings, and clips) weighed 305 grams. The Wiseco piston and pin each weighed 5 grams more than the stock part, but the rings and clips weighed 5 grams less, so just a 5 gram difference total.



Getting the top end buttoned up, I'm going with bare aluminum on the cylinder and head.

I also got some Boyesen #603 power reeds.


DT1 flat track project

The cylinder is at the machine shop for a bore job, and as soon as it gets back I'll be able to finish up the top end. I've got started on the wheels and forks. The rear wheel is from a '73 SC500 and the front a '73 TX650. I've got to clean up the hubs, and then install the bearings and lace them.

The '73 TX650 forks will be shaved and polished.



It was a nice snowy Sunday today in north central Indiana. Supposed to turn really bad tonight, with highs around -13 degrees F (-25 C) and 30 mph winds tomorrow. It looks like it won't be until Tuesday late afternoon that I'll try to dig out. These pictures are soon after the snow started. It looks like it'll be about 12" or more total. Hoping everyone in this stays safe.