besides dropping the port also roll in down with a long gentle roll like 1/4 inch or more , it all helps with the connection to the crankcase

Rich

Wow, Rich this is such good info.

Glad to help , But I only give so much info or I will be out of business 8o)

Rich

Get the head right. We are trying to build the dt the best it can be with the renowned low end and mid range with stock pipe, reeds, and for many even the stock silencer. Your engine should already have good compression otherwise when you rebore it down the line, compression could become too high for pump gas. The head will need re-moding then. You need to have at least 3/32 inch thick rosin core solder for checking the squish and a compression tester. There is power in the head as well as greater cooling, detonation resistance, more torque low to mid, better carburation. Take the head off and lay the solder across the piston so that it touches both sides of cylinder on the left side and the right (along the piston pin). The piston will rock the other way. A u bend made in the solder helps too. Install the head with the gasket. Bring the piston up with kick,squish the solder. Measure the tip of the solder with caliper. We only need the edge measurement. You might have 70 or 80 thou of an inch. We need that to be 50 thou or, some go less. Get a flat 12 by 12 piece of marble or granite and get some 220 wet or dry. Wet the paper and it should stick to the surface. You' ll get the hang. Use a figure 8 pattern, keep it flat. If it takes too long use a courser grade. Re check squish, repeat as many times til you have 50 thou inch squish. It is normal for one side of head to have different measurement then the other. I had gotten 49 thou inch on one side and 55 thou inch squish on the other. Final sand 400 grit or higher. Check compression. The dome will need sanding. Shoot for 145 lbs, that's what I did. It's good if you can cut down on the squish width, but only as far as what you need to go in opening the dome. Sand the dome with course sanding roll on dremmel, switching now and then with sandpaper. The head dome is really an inverted cone with a generous radius on both ends, rather than a parabola. So I tried to work the head to get a better parabolic shape. I got it a little better so that it lifted away from a straight edge in in the center. You can even do more to the head, as the squish band needs to follow the piston crown profile for most of it's width, but it doesn't. So I did this before sanding the gasket surface down, but gave up on it. I had a hard time afixing the sand paper to the piston crown. If you want to know I used 2 copper gaskets bolted to the head as a guide and some sand paper glued to the piston. I got more curve to the squish band profile.

Edit- notes. So you when you sand the dome you will be sanding away that hugh radius between the dome and squish band. This is a good thing. I believe a smaller radius will help cut down on detonation issues, and also no modern domes have such a large radius.

Interesting. I just ran the bike without the sparky/ silencer and the bike had less power than a moped litterally. Seems back pressure is totally needed. I probably will not look further for a used silencer, but I am sure there is some kind of sweet spot for aftermarket silencers. I was expecting some kind of power gain even though however lean the bike would run for the test. So after putting the silencer back on, back to the 30 plus ponies to the rear wheel. My bike is however mildly ported.

Gary Braun makes expansion chambers that work & fit. 612-913-2411

Yes I agree With what he said Gary Braun does excelent work. Here is his number 612-913-2411 If you want to talk performance mods give me a call 702-828-9177

Rich

RacerClam (Rich) installed the UFO in my 36mm carb for the DT1 and a notable improvement when you are rolling on the throttle out of a corner.

Rich, do you believe Gary could do an upswept pipe for the 400 as well.

Im sure he can , I have sent a customer of mine to him with a hONDA CR 125 AND HE IS building a high fatty pipe for him , I guess it depends on him having a bike to build it on . BEST to call him you gotmthe number

Rich