It's a big thread, but there is also that handy search thread feature.
That said, I looked through my own posts as I know I have given a few pointers over the years. I'm sure there are many other posts from others with better advice, but here are a few of my old posts to get you started. Some of these may be a little out of context as they were parts of conversations, but hopefully they help.
First thing first though...make sure your machine is perfectly level and I would at least start right at 6.5 deg. You can always tweak pitch to your liking later, but always start with it set-up as intended when trying to make things work right. It's a huge pet peeve when someone complains about shots not working right and you find out they are running at 7-8+ deg. Always at least start with the designers intent.
Here are some copy/pastes of my old posts:
After leveling and getting the slope right, you still might have to adjust the lane guides on the loop and the orbits, and also the Tatooine scoop. Make sure the guides are tightened down well too...mine were a bit loose from the factory making the shots inconsistent. Also make sure none of the targets are leaning far enough to interfere with the ball travel, and check the roll-under switch gate at the Death Star entrance and the left spinner to make sure they are not affecting the ball. My machine needed a TON of tweaking, most of any game I have had other than Avengers. It's worth it though...once it's dialed in it is a super fun machine and it has needed very little additional tweaking once it was done. Good luck!
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Some of it will honestly be trial and error. The first thing to check is make sure the lane guides are actually tight. Stern has had a nasty habit lately of not tightening posts and guides down well from the factory. If your guide is slightly loose and has some give, that could be enough to mess up the ball flow. If that's all good, before actually bending, loosen the mounting screws/nuts and see if there is any play in them. When re-tightening, put some pressure on the guide in the direction you want it to go to see if you can get it to snug up a hair in that direction. Sometimes that's enough. If you have to bend the end of your lane guide, do it carefully to not scratch it up or crack the mounts. And remember a very small amount can make a big difference.
Left inner loop (Death Star) should feed clean to the right flipper. Right inner loop (Hoth) should feed clean to the left flipper. If memory serves, there was much discussion about that early on, and that info came from Steve Ritchie himself (at least I think it did....fuzzy memory and too lazy to dig it up now). If you look at the geometry, you can see that is how it was designed to work.
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It is definitely possible that the overall shape is distorted a bit. In this case I would loosen the entire guide, make sure none of the attachment points are stressed, twisted, bent, or pulling it in the wrong direction, then tighten it back down. Also make sure the welds on the attachment points are good. I had a bad one which actually broke when tightening mine (not overtightened...it was partially broken already) and I had to replace the entire guide. With the bad weld, I do not think my original one ever could have been adjusted right. My new one was perfect with very little adjustment. So that is something to watch for too.
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Just remember that very small changes make a big difference. If you are bending anything so far you can't get it back in place, it's WAY too much. You likely do not need to remove the guide. Just loosen the mounting points, then push on the rails a little bit in the direction you want to change as you tighten them back up. In one case I found that from the factory my rail was tightened down with some tension that deformed them a bit. Once I loosened the nuts, the rail "sprung back" into shape, then all I had to do was tighten them back down. A little bit will do...a 1 mm in either direction is probably all you need! Good luck!
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Adjust your rails. Not very hard to do, but it's one of those things you have to feel out yourself to see which direction and how far you need to go. Lots of info in this thread if you dig a bit. Even when adjusted perfectly you might still have a random drain from them, but you should be able to get it 99% good. Mine took a LOT of tweaking, but was well worth it in the end. It could be as simple as them not being tightened properly, they might have some tension on them deflecting the geometry a bit, or they may need to actually be bent a bit. Remember a little goes a long way. Good luck!
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Hope this helps someone a little! Good luck!