Bicycle Mechanics - How much WD40 when cleaning sticky Shimano Shifters?

My left-hand shifter was stuck and a few squirts of WD40 did the trick. I also sprayed the right-hand shifter and it made shifting much better but WD40 came out filthy -- almost pure black. I sprayed it again with a good amount but it's still black. My question is, should I keep spraying the WD40 in the right shifter until it drips out clean or just leave it alone?

Keep going until it's clean. WD-40 is cheap, brifters are not.

Keep spraying until it runs clear, and then spray some more. Put plenty of newspaper under the brifters. It's impossible to spray too much WD-40 but that black gunk will stain.

Thanks guys. After it runs clear, do you let it air dry for a few days and then re-coat with something like Tri-flow?

I generally don't use WD-40 for this and instead use Tri-Flow spray or White Lightning Clean Streak for especially bad shifters. I'll spray into any accessible area until the shifter works freely. Tri-Flow has seemed to work well alone. I assume WD-40 would be enough to keep it working by itself or you could do some Tri-Flow later if you like.

I'd let the WD-40 evaporate for a few hours then lube the internals wit a lot of Tri-Flow. WD-40 is basically OMS (odorless mineral spirits, a near cousin to kerosene) with a small amount of a special water displacing oil. It's a good cleaner and very light duty lube. I like to lube with something a bit more durable.

For fun, I have been rebuilding those old '90s era Shimano shifters at my local bike coop. Almost every one that we have is sticky and barely shifts if at all. The problem is that the grease they used gets hard and sticky. Now I have just sprayed the snot out of them with WD-40 and gotten them freed up but they aren't perfect. The pawls just get gummed up like crazy with the sticky/hard grease and don't flick back like they should.

I will disassemble the shifter starting at the top of it. Quite often the nuts are reverse threads at the top of the shifter. I then place each part in a line on the table. I then use WD40/rubbing alcohol/whatever to clean all the crap out of them. I pay particular attention to the pawls and the pivot points. After i put it back together, they usually work wonderfully and like new. I generally just use a 3-1 oil or PB Blaster lubricant for lube after they are cleaned. I do not use WD40 as the lube.

WD is mostly solvents, you can also use kerosene , flush out the crud.
then lubricate with something else, as suggested.

A more effective, if laborious and equipment intensive, way to clean a gummed up STI brifter is to remove the cables and push out the brake lever pivot pin. The pivot pin has a small set screw underneath that has to be removed and a small return spring so pay attention to how it's placed before you remove anything. Once the pin is out, the entire shifter/brake lever assembly can be removed from the body. Place this assembly in a jar full of OMS or Kerosene and either shake it frequently or, better yet, agitate the solvent continuously. A lab magnetic stirrer is great for this or, ideally, an ultrasonic cleaner bath. Let it soak for several hours with frequent shaking or agitation. You will be amazed at what comes out in the solvent. If it is really dirty, change the solvent a time or two.

After several hours remove the shift/brake lever assembly and drain and shake off the solvent. Let it dry for a few hours and lube copiously with Tri-Flow or similar oil. Then reassemble and reconnect the cables.

TRI-flow kicks ass! cleans and lubes. fixed both my deore shifters