Usually a ufo requires ony a pilot jet change , In Toms I installed a #20

Rich

That bike is really cool! Just dont fall off the back of the seat !

Rich

Get a new pipe made. I am glad the discussion turned toward this. A good pipe designer, keep your fingers crossed, can design a pipe that should even increase low end torque, mid, and a little on top. Maybe 3 or more hp. The reason is the stock pipe has so many inefficiencies. Or the pipe can keep the same low end, but increase more in the mid range and a little more on top, making more ponies. Alot of possibilities. Not a pipe designer by any means. I called Gary, but I have also tried others. It's about time someone made one for these years 77/78. It would be cool to have a plug and play pipe. And if the 77/78 dt250 is the same as the 400's that's a bonus for those as well.

Jemco Exaust can still make a pipe for that 713-461-3834 And if you want the ultimate call Gary and at a minimum call Dave Meis and have him modify your pipe to his sleeper pipe

Rich

I tried jemco years ago, no interest. Don't mean he won't now, however. I think we should all call pipe makers to make one. Years ago I tried dg pipes. Since then many new pipe makers on the market.

I talked to Can at jemco about 3 months ago and he said he would make it , So who knows

Rich

Not can but Dan

Doesn't a Dt400 deserve a bigger carb. While some have gotten carbs from China or mikuni, maybe with or without installation issues to overcome, why not work with what we got. I am talking oval boring the carb. There should not be a loss of low end torque, which is what these posts are all about. Do at your own risk.. Disassemble the carb. Put in a vise upside down. I highly reccomend a dremmel with a rough sanding roll and a medium half round cross cut file. Work the top half of the carb to a cressent shape. The top half I mean when the carb is positioned upright, the upper half. Switch many times back and fourth between the sanding roll and file to ensure a smooth shape radially and a flat shape forward to back between the raised area of the belmouth inlet to the throat of the carb at the manifold. Run the file without lifting helps. Marks that don't go away are low points so carefully watch the pattern, front to back and side to side. It is easier than this is sounding. Make your cresent start at the halfway point of the throat from nil to (x)mm' s at the top. At about 1mm watch that you don't go through the choke breather in the belmouth. I went 1mm with my carb, but careful working around the breather you can go more- perhaps 1.5 mm. So other work includes going a little higher on the main, and also matching your intake manifold to the larger throat (different shape) of the carb.

Open up the breather box. I am throughly convinced that the stock oem filter is the best that you can get, and does not restrict flow. It is the breather box inlet. Not sure of any performance increase. If you do make sure that the lid cover is not compromised as, it provides support for the seat. I opened mine and not sure if you have to rejet. If so it might be one size. Cut or drill as high as possible so that water does not get injested into the motor. With my ported motor and oval bored carb I am running a 200 main. But that is mildly ported, which these articles are not about.

Just my thoughts, do at your own risk at what is said here. I want to talk about improving the flow of the ports and passages. Not port blue printing or a clean up per say but things that may work. Starting with the crank case as the Piston starts to rise and create suction. Rich aluded to case reed induction being better than cylinder reed induction. So we want the flow I am guessing to mostly go into the crank case. Otherwise it follows mostly up with the Piston. The mixture down low is better ablte to get to the transfer entry ways than following the Piston up and then down and having to turn sharply up into the transfer entryways. So how do we improve flow from the intake. First all the Piston windows at bdc (stock size, over bored piston has slightly larger windows) do not allow flow into the port opening until almost 1/4 inch of upward piston movement. So grinding the top of the windows higher will get the intake mixture movi g sooner through the port into the crankcase. Another thing as Rich stated i believe is to turn down the bottom of the intake with a hugh radius to get the mixture going down under the transfer entry ways. Sorry again Rich if I got it wrong. Might as well drop the floor a little while there. I don't believe about hogging out the entire port window just the bottom for a stock Dt. Just my opinion on keeping velocity high. So next my theory on the crankcase as when the Piston is traveling down and the mixture is being forced into the entry ways..I would appreciate comments from all.