pilot air screw stuck

[firstGSrider]

I've been taking my carbs apart and I have all four of them done except on one of them the cap for the pilot air screw was kind of difficult. I managed to get it out but think I might have damaged the threads in doing so because the screw will not budge. The other three came out fairly easy but this one won't move at all. I have tried heat and penetrating oil and it hasn't moved at all. It has started to chip some metal off the top of the screw. What are my options? Do I need to get a replacement carb if the screw won't come out? The more I try now the worse the screw head gets. Also my diaphragms are slightly cracked on the rubber. Should I replace these or are they probably okay?

[Steve]

The good news is that your "pilot air screw" is NOT stuck.
Mainly because you don't have one.

What you do have is an "idle mixture adjustment screw".

Since you are apparently starting to damage the slot, your next move will be to use some penetrating fluid (hint: WD-40 is NOT penetrating fluid) and let it soak into the threads for a while. Heat the tower around the screw to break the corrosion free. The last step is the one that usually works for me: cut a new slot. Use a larte cut-off wheel in your Dremel rotary tool, cut all the way down the tower, put a new slot on the top of the screw.





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[firstGSrider]

Okay thanks. Yeah do excuse the ignorance i'm new at this. I'll def try the new slot. I am worried that the threads are possibly damaged in the channel so hopefully this will help. Thanks

[cableguy]

firm pressure on the screwdriver and make sure the blade of screwdriver fills up the slot as much as possible. Then work it little by little, and as you (hopefully) get it to turn CCW, work it back it back and forth a couple times, then see if you can turn it out a little more, then back and forth, lots of PB, etc etc....The threads will load up if you don't work it back in, and copious penetrant will hopefully float some of the gunk away. There's always drilling if that doesn't work :0)

[trippivot]

Butane pencil torch or a general propane torch with a light touch will help the extraction. Don't blow your self up. I've done it many times - it's a secret procedure that I charge hundreds of dollars to do.


Everyone is a bike mechanic, it is the dental surgeons that can restore mutilated carbs back to proper operation.

[Guy]

Okay thanks. Yeah do excuse the ignorance i'm new at this. I'll def try the new slot. I am worried that the threads are possibly damaged in the channel so hopefully this will help. Thanks

They're very fine threads and easily damaged, take your time. A cook's blowtorch is handy for heating small areas like carb parts.

BTW, don't apologize for calling it a 'pilot air screw', he knew what you meant. Idle mixture screws are often referred to as 'pilot screws'. Generally speaking, if it's on the top of the carb it controls the air, if it's underneath it controls the fuel.

[Bustedknuckles]

one thing ive had to do before as a last resort was to use a small bolt extractor, it worked great though, here's the procedure.... use a drill press to CAREFULLY drill a small hole into the MIDDLE of the screw, if your off center by too much theres a good chance the tip of the bolt extractor will snap off, then you have hardened steel in you jet... (not good)

Get the largest bolt extractor possible, that will still fit into the hole... this reduces the chances of it snapping off.

when finnaly putting the bolt extractor into the jet, apply pressure to make sure the extractor seats into the jet, once its down into the hole enough, STOP applying pressure and slowly start backing the screw out... if you are still pressing down on it you are hindering the removal process... it wants to come out, so dont push it in... Only press down while the extractor is biting in and threading itself into the jet. if you do everything right there is almost no bolt that cant be removed...

and of course, the more heat and penetrating oil the better...

[Nessism]

Heat, penetrating lube (not WD-40), and a tight fitting screwdriver are the keys. Oh, and not buggering the slot of course. If the screw is stuck, STOP before you damage it. Add the pent. lube and heat it up. The lube really works down into the threads when you heat up the carb body.

[Mercaholic]

Heat, penetrating lube (not WD-40), and a tight fitting screwdriver are the keys. Oh, and not buggering the slot of course. If the screw is stuck, STOP before you damage it. Add the pent. lube and heat it up. The lube really works down into the threads when you heat up the carb body.

Just to add a tip that worked for me is to rest the correctly sized screw driver on the head of the screw and tap it with a hammer. This will help jolt the screw while in place and well lubed, prior to twisting is CCW.