I'm going to show you how to disassemble and reassemble a Shimano RSX STI type shifter this is the left-hand shifter the sweet three-speed shifter and to start off with there's a little lock screw right here it's a two millimeter hex screw I'm going to go ahead and loosen that this could be real tight but this one is it and we don't need to remove it all the way just kind of like loosen it a lot there so it's sticking out there now this pin right here I'm going to use like a four millimeter allen wrench and just go ahead and push this pin out and I may need to compress the the brake lever a little bit but I pushed that out this comes out the other side here and there it is right there so set that aside pull that out and then I can pull this apart and then there's no little parts in here to really worry about on this side there's a spring and two little bushings I'm gonna go ahead and pull the spring out just so keep it out of the way there there's the spring at the side and then there's a long bushing and a short bushing the long base pushing goes on the side with this little hole here where the spring attaches so I'm going to push that out of the way because it's gonna get in the way in a little bit okay next thing I'm gonna do is I'm remove the front cover here and then that's a five millimeter allen wrench let's go ahead and remove this little bolt on the front and there's a bolt and then there's a little lock washer on there so make sure you get the lock washer because sometimes it might stay down in there and then this front little cover I can go ahead and pull that off and be careful because there's a spring in here as well and you want to notice note the orientation of the spring on this particular one this is how the front cover went on so the cable will come in this side the spring attaches down on the bottom here and then the other prong comes up on this side over here so you want to remember that now there's a couple other little parts in here you want to keep track of there's a little ring around here that's just sitting into it like a little notch in there that could fall out there's also a little bushing in there that might possibly fall out no I want to go ahead and remove this this big leaver here and how that's done is I'm going to take this small lever push off the side and exposes a little Phillips head screw down there and I'm gonna go ahead and remove that then I can use like a little Phillips head screwdriver here and remove that and there's that screw there it was just this aside now at this point I can go ahead and lift the big lever off there and be careful there's like a little square part right here like a little thing here that can fall out so keep track of where that is we'll set that aside and this one well there's a little plastic housing here and it's broken on this one so it falls off don't worry about that okay so now here's the shifting mechanism in here all nice and exposed what happens one of reasons that these things stopped working is the old grease just gets all gunked up and doesn't allow the little spring parts in here to move properly so if that's the case you can go ahead and clean off all that old grease using like a solvent and then just remove the whole thing up and just to show you how the mechanism in here works is like that there's this little part and here where the cable attaches if I go ahead and shift it it pulls it one notch and I pull it again to shift it pulls it another notch and if I do the little leaver there it releases the one release again and that's how this whole shifter works so now I'm gonna go ahead and put this thing all back together again so what I'm going to do is take this big lever here and I'm gonna go ahead and put that plastic thing back in a little bit later because it'll keep falling out here and I'm gonna go ahead and set the shifter unit back in there and then you want to make sure that this part down here falls in nice nicely into there gets all like lined up in there and I'm gonna take the small Phillips head screw and I'm use that needle noses just leave these are to get that into place there push that aside there and get get that lined up in there and then screw that in you can use a little bit of a threadlocker purple low-strength threadlocker locked tight - - - but basically and put that on the threads of this screw ok so I got that screwed in now ok now I can go ahead and put the front cover on and I've got the spring here and again I want to make sure that so that the one little notch or the win little part of the spring goes down in this little hole here and I guess again really only got go on like this or like this doesn't matter but you want to make sure that this little part is up on that side now the trick to this is there's a little notch down in here there's no little notch up to there but you'll want to use this when you use this and that little notch down there that's where this little spring tip is going to go so now when it's in position it's going to be like this but how we're going to line it to get that spring in there is it's going to go this so it's facing up so we get that spring tip in there and suit notice how this little part is lined up there and the little part coming up there Square and this little square so what we do is we rotate this 90 degrees and push it down and as I sort of lock into place and that in that position then I'm going to go ahead and take the screw screw this in it started here there we go and then this is five millimeter let's go ahead and tighten this down and again you can use a little bit of a threadlocker purple on here or lock type ii ii ii type mess okay now i'm gonna go ahead and put this little plastic part back in cuz once again in here it's not gonna keep falling out she get a little bit of glue and kind of glue that back in where it's busted okay now comes the hard part this part down here is okay i'm gonna go ahead and put this long bushing in again this long bish is to go in on the side where this little hole is where the spring attaches and i'm get this little spring here it's leisure if you use some needle noses if i put this a little part down in there a little hook there that's gonna go down in the hole and let the rest of it just kind of fall over the bushing there now I have this other little tool here it's like a little little tube it's from Shimano it's an STI return spring install pin part number is ts03g l st zero to either one of those will work and all this does it's like a little sleeve a little tube it's just gonna fit over this part of the spring here like that that's all it's going to do now this is the hardest part is getting this part together is I want to get these little parts here fitting over this while keeping that spring in there so trying to get this together and push it into place and oh I think it's gonna go a little relatively easy and you could get these holes lined up there now I've got this little pin here there's a little notice the notches off centered well so is this little lock screw there it's going to go there so this little notch there is going to fit line up with that little screw there now the easiest way to install this pin is on the side that the spring is so go ahead line this up get lined up at the hole there and then get it pushed in okay once you get it in a little bit then the rest comes a little bit easier so you have moved this around get push it in and get it lined up try to get a little farther okay there I got it in farther get to the last part lined up there and got it okay I can push it in the rest of the way get centered now at this point this little little tool I go ahead and just remove that now all this left to do is tighten this little lock screw and again you can use a little bit of a thread lock or purple on there just screw that in and then tighten it down and there how you have it all back together so now just go ahead and you can test it shift shift shift shift and that is how you disassemble and reassemble a somato RS x STI left-hand shifter just like that hope that helps