A surge on a steady cruising throttle is a common complaint on the big bore DT's .
Richening the pilot circuit has been known to reduce this effect somewhat .
Try turning in the pilot air screw 1/4 or 1/2 a turn , or go up a size on the pilot jet itself .
From others experience , you probably won't eliminate it entirely , but it will be less annoying .

Terms change, but i wouldn't call that "four stroking".

The behavior you're describing goes all the way to when these bikes were new. Magazines wrote about it. Many threads on here about it... and even service bulletins on the earlier 360.

As Dave said, it's part of the 360 "personality".

The solution to this undesirable DT360A personality trait seems to be some crankcase stuffing. I've had good results with cleaner running at low throttle positions and a stronger idle. The best place to epoxy is down in the cases but I didnt split the motor apart just for an experiment. I probably will now though.

I started with a large amount of epoxy in the gigantic main transfer tunnels. This can be done relatively easily.

Hi msavitt I currently have 2 360's and 3 400's. I have noticed this problem on all of them when cruising with no load on the engine. If your going uphill at the same speed it clears up but comes back on the level. I remember this from when the bikes were new and they did it then also. Since I have such a hard time staying on pavement for more than a couple of miles at a time I never really spent much time trying to clear it up. My complaint more that at cruising speed is when your decelerating and its popping and banging and making unusual vibration unless you pull in the clutch and let it get to idle. I did notice the 250's ands smaller bike don't have the problem. No help but your not alone
doug

turbodan, run103, MarkT - this is truly fascinating! you guys and the article describe my engine to a tee! I am going to just enjoy it as is and hold on tight and make sure that I stay pointing in the correct direction when at this operational point and just enjoy the history and save my cash!