This will reduce the obstruction force of teflon tube to filament.
Works fine with PETG!
(Ignore the missing teflon tube on the left, not installed yet)
PS. High speed printing may make PETG very friable. I use the speed wall 40mm /fill 60mm.
Erm, where will that part fit? For the life of me I could not detect it on the upper picture… 
You mean the second picture?
Oh, the second picture is just the print result, not a part of the solution.
Only need to replace the teflon tube and make drag chain shorter.
I see. Thanks for the clarification.
Hard to tell from the photos, but it looks like your modification was to cut out and remove a section of the PTFE tube. Is that correct?
Yes. but I cut a new tube.
The original one is still intact.
I would highly recommend against this modification and would suggest that you put the full PTFE tube back in place. None of the clogging issues people are experiencing are related to friction in the PTFE tube. Your modification will significantly increase the loads on the X/Y motion system and the extruder as well as opening up the potential to fracture more brittle filaments. If you are having trouble visualizing the potential problems with your modification, I would suggest this simple experiment… Move your right extruder to the far right and far rear of your machine (top right corner in your photo). Then, wind up all slack filament back onto the spool. Now, hold the filament spool tight and try to home your machine. You will either cause the X/Y axis to skip steps, cause the extruder to slip, and/or break your filament. For a second exercise, without touching the spool, move your right extruder to the far left and front of your machine (bottom left in your photo). Now, move the extruder to the opposite corner (top right in your photo) and watch what happens to the loose filament. Picture that movement happening repeatedly at high speeds, and it you will see what a mess it will make of your filament.
I3 style machines don’t need the PTFE tube because the distance from the spool to the print head changes only by a centimeter or two as the print head cycles back and forth. On your J1, the distance from the print head to the spool can change by over 30 centimeters in a single layer.
If you really want to try running your printer without the PTFE tube, you will need to remove the top cover from your printer and then suspend your spools at least 30 centimeters above the center of your printer. This would bypass all PTFE tubes and the filament would run straight down to the extruder, similar to an I3 style machine.
I understand the logic, but if this really helps, I would rather try a good Capricorn XS tube than shortening the original one like this. If you take a look at the earlier Videos of the J1, you can see that the team did not have a filament guide tube earlier. I guess they had good reasons to add one.
By the way, could someone measure the total length of the guide tubes?
Thanks for your suggestion！This modification does affect the load on the x-y axis during high-speed printing. However, the obstruction force of teflon tube is really too large, will also affect the extrusion.
In essence, clogging is caused by the design bug of the heat break. This can only be solved by the official. I hope it can be solved.
The second solution: (but the box will not be sealed)
Someone has tried Capricorn XS tube, but he said it was not helpful.
length is 60cm
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I raised the speed at wall 60mm /fill 80mm. after 15hours of large-area printing test
solution 1 failed, still clogging. 
solution 2 passed.(but can’t sealed the box)
solution 2：
solution 3, remove the drag chain, pull the teflon tube out a little on extruder side to reduce the obstruction force. Then can seal the box
still testing. so far so good.
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at last, raise temp is the final solution
I set temp 260（material recommended max temp is 250）/outer wall 50/inner wall 70/fill 100
I made some simple modifications to reduce obstruction force of teflon tube.
result is good. no clogging happened.
Especially these grids, will cause a lot of retraction. they are perfectly printed.
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