They have made a few different models since 1903 :>D
Most are available via Google, but a paper copy is better.
year make model repair manual
https://www.google.com/search?q=2000+Harley+FLHTCUI+repair+manual
Or search this website. We had a great Expert hear named Greg Mahin, but I think he has passed. He was an ex Harley dealer and posted links and videos to every HD problem
https://www.fixya.com/search.aspx?ref=ser&s=greg%20mahin&
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Question edited for full maker name.
Question moved from Cars and Trucks.
Your question is missing the model and they make a few!
Google
year make model replacement push rods
see if they come as front and rear or as a pair the same. I would imaging they are the same and the lifters need adjusting. That can also be found on Google. Many of the workshop manuals are free online.
Question edited for clarity and Maker name.
Question moved to Make / Model category.
That means it is a transient fault. The ECM finds an issue and then on rechecking, it goes away so the light goes off. You will either have to catch the code when it happens or wait for the fault so show up all the time. A dealer may have a scan tool that can record the fault when it happens like a pro grade scan tool computer for a car can.
Question edited for FULL 'year make model'.
Question moved from 'Power Motorcycles' to correct category.
Help in the link, crank sensor or ignition module are the most likely causes.
https://www.google.com/search?q=2001+fxdl+no+spark
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I wouldn't close either one, the crankcase needs to breathe. lower one can be routed under the bike. whether you add a catch can, or just leave it open is up to you. The one at the head was originally designed to feed back into the carburetor and run through the motor. If it has a bypass, it was put on to avoid that. The bike will run better as is, when compared to shoving all that gunk back into the cylinder and choking it out, the way emissions wants you to do it.