My sr was doing this and its very annoying so this is how I timed mine correctly. First I removed the spark plugs and made sure my crank was not at tdc but below it (So no valves contact the pistons). Next I lined up my exhaust cam at tdc and then I take the intake sprocket itself off once I see the intake cam is at 10 o ' Clock. Last you will put the chain on the intake cam sprocket and put it on the intake cam and bolt it in and tighten down. The real trick to this is that notice how the intake camshaft has a dowel pin that aligns with the intake cam sprocket itself. Okay so when you put the chain on the sprocket and you line it up with your intake camshaft notice how sometimes the dowel will be a little bit off even in that 10 0 clock general position I say general because the sr20 will snap into 10 o clock and allow a little play before snapping into its next position. So what I use as an assistant is that as I am trying to put that intake cam sprocket back on the intake cam with the dowel pin lined up with the sprocket Ill take a large I wanna say 26 mm wrench maybe and use that to lightly turn the camshaft just a little bit to get that dowel pin in (You will need to remove rocker arm stoppers for this to work IF you turn the cam itself with the wrench without sprocket on it the cam has an area where a wrench can grab it obviously). Also it will look like the dowl pin almost does not want to go in, but it is lined up THIS is how you know you did it correctly because once you tighten the intake cam bolt down the dowel will go in perfectly the reason why it is like this is because with the chain on the sprocket it almost goes on at a very slight angle and not truly straight, but still just tighten it down and it will go into position. It will definitely take you a few tries to correctly do this Id say it took me at least 40 minutes to an hour just to do this very annoying last I just set the crank at tdc so dont move it too far off tdc just enough to where your valves wont touch the pistons, but also to where you can slide it back to TDC without the chain spinning the cams. I know this sounds confusing, but I hope that makes sense and helps. I say it takes a few tries because the first 2-3 times I did it I was 19 links between the dots eventually I was at the perfect 20 after I did what I told you. Also Those colored links do not matter and are only used for initial engine setup do not bother trying to get them correct as long as your 20 dots at the cams and crank is tdc you are done.
https://www.youtube.com/watch?v=nmBYYtOXF-o