I wouldn't use a helicoil in that situation, if the thread is damaged at the start of the thread I would use a tap but I would first remove part 4 from the tube it attaches to so you can clean out any metal swarf trapped inside so it doesn't enter the brake line tube. The rear shock is surprisingly easy to remove and doesn't take long so removing that will probably give you more room.
With the bike on it's center stand, support the rear wheel with a floor jack to take the weight off the mounting bolts. There are only the two bolts and the only hard part of that is the nut for the top mount is a little harder to get to but you can probably get it with a pair of needle nose pliers. Then just one bolt holds the adjuster under the seat. Realistically you could have the shock off in half an hour.
When you try to replace the banjo bolt again be very careful with alignment of the thread. My guess is that the brake line you were trying to attach may have dragged you off line a little with the start of the thread. When you get the thread cleaned up try the banjo bolt without the line first. It should go in easy. Then when you try it with the line make sure it still feels as easy. If it doesn't, remove it and try again, never force these threads.

 

I was attaching the banjo bolt to the upper brake line under the rear shock and it won't attach. The banjo bolt thread is good but starting thread in the hole is not and I can't reattach. Anyone have some ideas before I ruin it more than I did already. should I use a TAP to clean out it out or should I go a heilcoil? Any help appreciated. I guess last case scenario I could order the new part, but will that require remove the rear shock? Kicking myself in the butt. View attachment 171578

A picture of the thread condition in the part would help a lot. If just the first thread is damaged a little, cleaning it up is probably OK. If two or more threads are damaged very heavily, it is probably better to bite the bullet and replace the part. Brakes see very high pressures and these parts often only have 4-6 threads engaged. If you lose 2-3 of those, you have lost potentially have the tensile strength and that is not a good think in a system as important as the brakes. If this bolt held on a mirror or license plate, it would not matter much, but brakes are different.

 

Definitely just try (gently!) to get the bolt threaded without the hose. The smallest burr on the end thread of the bolt is enough to really screw things up, so check that out and use a new bolt if needed. It's much less likely that the threads on the fitting are bad IMO. Unless you are completely insensitive to what you are doing, it's nearly impossible that the damage goes a whole thread or more deep.

Once you have the bolt going into the fitting, then just duplicate that with the hose in place, making sure to keep the hose flat against the fitting so it doesn't try to cock the bolt sidways again.

I have fought with this a few times.

 

Also that fitting is at a bad angle so I recommend undoing the bolt (item #5) to allow you to get the bajo straight onto the fitting. I usually remove the shock when I do brake lines to allow better access to that fitting.

 

Don't know if this applies to your situ, but I had trouble with the Speigler bolts so I just re-used the OE banjo bolts with fresh washers.

 

Two of the bolts Spiegler sent to me were the wrong thread pitch. Took a little arguing and a couple of photos to convince them I was correct, but they finally sent me two more with the correct thread pitch. I didn’t notice the difference until I tried to attach a front caliper banjo and could not get the bolt to go in properly. I always turn bolts at least 3 full turns by hand and if they won’t go that far, I know something is amiss. Thankfully, my calibrated fingers picked up the problem pretty quickly and a comparison to an OEM bolt quickly highlighted the problem.

 

I can help out if you need a replacement part. That bracket and bolt was the bane of my existence not too long ago.