What I did to prevent the J1 extruders clogging

[FlashErase]

Because I was afraid to rebuild the hot end that the overall length is no longer correct and special adapters are necessary, I limited myself to conversions that did not require any serious interventions in the hotends.
Here the changes I carried out:

• High-quality thermal paste applied on the cooler side of the heatbreaks
• Original extruder gears replaced by the gears by Bondtech ( https://www.3djake.de/bondtech/drivegear-kit-fuer-175-mm?sai=3018 )
• Replacement of the stock brass nozzles with hardened steel nozzles with 3-way copper core ( https://www.aliexpress.com/item/1005006680607298.html )
• The Hotend temperature I increased by 5 degrees for al materials because of the steel nozzles
• Lifting of the top lid for better filament guidance ( Printables )
• Replacement of the original filament inlet by one with smoother bend ( Printables )
• Moving the filament coils into the inner of the printer, using Teflon hose with 3mm ID to reduce friction ( Printables )

After applying all these modifications I didn’t got a clogged extruder during all following prints.
I hope this will help you to fix the clogging issues on your printer too.

[FlashErase]

Had recently a 15h-job for the modified printer. It was processed without one clogging issue.
Printed it with PLA silk silver at 225°C, a 0.4mm nozzle at 150mm/s.

[Stelzer]

I had to replace the PTFE tube in the heatbreak with Capricorn tubing 1.9mm and using 40mm retraction in the slicer. Clogging was gone. I couldn’t print white or rock white PLA at all in 2 color mode.

[FlashErase]

Yes, all actions reducing the friction within the filament path will help to prevent the clogging.
But 40mm retraction!? This seems a bit too much in my eyes. Even on my FlashForge printer I used at most 5mm for flexible filaments and PETG.

[Stelzer]

That’s the retraction used when switching filaments. Not normal retraction. This is set to 0.4mm in my case. Standard retraction when switching filament is 2mm in orca slicer.

And i use the Capricorn tube because the diameter is smaller. Thus when I switch filament the tip will get parket at the ptfe tube position and the tip will be small enough to enter the nozzle again and not jam/clog in the hotend.