First, I think most of the mini H1 projector will works great without any high beam stuck problem, but you never know you are one of the unlucky guy until you finished your retro and used your headlight for some time. So, why not take some extra 10-15 mins to prep your mini before putting into your headlight?
Please read through the entire thread for various tips n tricks associated with using the Mini Morimoto projectors in your retrofit
Alright, let's start.....
First you got to unscrew all four screws which holding the front part and the bowl.
With the latest gen of mini H1, there are a washer and a lock washer for each screw. Make sure you don't lose them.
There are two small screws holding the solenoid to the cutoff shield. Unscrew them and you should able to move the solenoid so that you can take the solenoid plunger out. (You can leave the solenoid wire looping with the cutoff shield assembly, I just take the whole thing out for taking pictures)
Now, if you want to be sure it never gets stuck in high beam mode, you could stretch the return spring. Beware this may increase the chances that the solenoid wont be able to pull it into high beam mode in the first place though.
Take return spring out from the plunger.
Mount the plunger onto a drill like a drill bit. Get a coarse sandpaper and pushing it onto the plunger, then switch on the drill and sand the plunger a little bit smaller.
Just sand it down a bit. Then repeat with a fine sand paper so that the surface is smooth, and you should end up with something like this.
Now you are ready to apply lube on the plunger. What I used is a graphite lube which will works under high temperature. Put the plunger into a big box and fixed it with some tapes, then apply a light coat of graphite lube around the plunger.
Now you got a plunger with a little bit smaller in diameter and lubed by graphite.
Put the return spring back to the plunger. The spring should insert from top, so that it won't remove the graphite lube from the plunger surface. The lower groove is the one to hold the spring, not the upper one.
Now you just need to put everything back together and you are done.