DT1 flat track project

I got the DT3 bottom end that I'd bought on ebay taken apart for the rebuild. It looks to be in good shape. The connecting rod axial and side play are all within spec, the big end bearing feels fine, and no sign of any rust or moisture damage, so I'll likely end up just cleaning it up and using the crankshaft as is. I've got lots of cleaning to do on the cases, and I'll get new bearings and seals ordered. I used a steering wheel puller to remove the crank from the main bearings, but will need to either buy or make a tool to reinstall.

DT1 flat track project

I got a start on the chassis assembly. I got some new shock bolts and a fender mount kit from ebay seller motodad24. He has some really nice parts at great prices.


The '71 and up round tube swingarms can use standard XS650 aftermarket bronze bushings, but the early swingarms use smaller bushings, so I got a new set of stock nylon bushings from boats.net.


I'm using All Balls tapered bearings up front.


The top race of the tapered bearings sticks out from the steering head slightly increasing the distance between the fork clamps. This isn't an issue with mine since it won't have a headlight, but can cause problems if using stock headlight mounts, so you can get just the lower tapered bearing part #99-3515-5 and use stock balls on the top. The bottom takes most all of the load.






Here are the mx clamps. I spent some time on the bottom clamp, but just brass brushed the top for now. I still need to get new hardware for them.

Kurt Caselli RIP

DT1 flat track project

A little breezy, but otherwise a decent day for painting, so I got most of it done including the frame. I used Dupli-Color self-etching primer and gloss black, and it came out very nice. I've still got a little bodywork to do on the rear fender before paint.




I also made an engine stand and started taking apart the '72 engine with the broken case to see what is usable. So far it looks pretty good, and has a standard bore cylinder which is good news.

DT1 flat track project

I got the sandblasting finished on the DT. It isn't much fun, but the results are worth it. Here is the inside of the rear fender before...


...and after.


Here is the RT2 seat pan. It had a few cracks to weld up, but very solid otherwise.


I also painted the seat pan and exhaust after sandblasting.


The paint is VHT flat black exhaust paint.




This frame is older than me, but looks brand new. The frame and swingarm will be black.

DT1 flat track project

The bike is torn down for the finish work, and I scored a '72 RT2 seat on ebay this week. I'll get the sandblasting done this weekend, and hopefully will get a day or two warm enough for painting before it gets too cold. I'm getting the paint done first since I can do the engine and aluminum parts in the basement over the winter.

DT1 flat track project

I finished the swingarm. Hopefully it'll make the bike less likely to throw me off when getting sideways.


The SC500 wheel got here. It'll get polished and new spokes, and a high shouldered rim will be laced on the front to match.


I still need to check that the wheel is centered and the sprockets line up, but it looks like all that I'll need is a couple washers to make up for the axle plates being narrower on the early swingarm. I'm still leaning toward using a stock rear fender and seat, so I borrowed the ratty seat from my DT3 to see how it looks. I'll need to find another one for this bike. It should be ready for tear down by the end of the week, and then the real work will begin.

DT1 flat track project

I welded up the exhaust and the front mounts for the gas tank.


For the rear tank mount I got a new reproduction from CSM Restoration Parts, the same place I got the mount for the CT1 tank on the '79 XS650.


The engine rebuild will be starting soon, and one problem with the DT2 engine in the bike is a broken case at the shift shaft. This was likely from a chain breaking, and likely the reason the bike was parked. It is possible to weld this, but I figured replacement would be better.


Looking at replacement cases on ebay, I found a DT3 bottom end for $64.99 with free shipping. That's a deal since I also get a spare transmission and crankshaft.


When the DT1 came out in '68 it quickly got a reputation as having nervous handling. One popular mod with the DT1 is lowering the engine cradle and swingarm pivot. It is supposed to lower the center of gravity and reduce the swingarm angle, so an option I looked at. It kinda makes sense, but since it reduces ground clearance anyway, it also sounds like a more complicated way of what could be achieved by just lowering the entire bike. I started comparing the '68 frame with my '73 DT3, and about the only frame geometry difference I noticed is a 1" longer swingarm on the '73. A later, longer round tube swingarm can be fit, but I wanted to keep the early square swingarm, so decided to stretch it.


The rear axle to lower shock mount distance is the same on the '68 and '73 swingarms, so the longer arm also moves the shock mount back, changing the shock angle, one of the reasons I decided to stretch the front rather than extending the axle plates.




I needed slugs for the square tubing, so started with angle stock.


After welding and grinding I have a piece of square tubing to cut the slugs from.


I did some mock-up, and a 1.5" stretch looked about right.


Here is how the slugs fit to the front part of the swingarm.


Since the swingarm tubing isn't square to each other I needed to cut slots to allow the slugs to slide in.


Here is how it all fits together. After welding in the slugs, it will then get skinned to look like it came from the factory.


The pieces fit tight enough to mock it up and see how it's looking before welding it up. It is a bit lower, longer, and with less swingarm droop and more shock angle than before. It'll be interesting to see how it handles. I'll also need a longer brake stay and brake rod. I'll finish the swingarm this weekend. I've got a '73 SC500 rear wheel on the way. I think it is the same wheel as a DT2MX, so it should fit right in.