stripped head on the pilot adj screw

I was cleaning a friends kz750 twin cylinder carbs and when i when to remove the pilot adjusting screw i noticed the screw head was partly stripped. I tried to get it out but it was stuck tight and i ended up stripping the head all the way.

Question: Whats the best way to attempt to remove this pilot adjusting screw? Have anyone been successful in removing these screws? Or should I even be concerned with the screw? The bike ran fine before it was parked about 2 years ago. and i only cleaned the pilot jets and the main jets.

tw

My question is...why was the screw in there so tight in the first place?...they're brass,and they only need to be snugged into place,but anyway...
Can You get in there with a screw/bolt extractor?...

that was my same question "why is this thing so tight"?

yes i can get at it with a drill or extractor. it's the screw on the outside of the carb for adjusting the air mixture for the pilot jet.

I drilled one out. It was a PITA. I did it alot like a root canal. I think I used a 1/16" drill bit and slowly went at it. The screw is fairly long, but you dont want to go ballistic on it. Then I went bigger to get the threaded part at the top out.

I might still have some remains. I will post a pic if I do.

Well i drilled out the pilot adj. screw and as it turns out someone must have put some of thread sealer cause the threaded part of screw still won't budge. i got the pointed end out just fine but threaded part is stuck. I even tried an ez-out but that bad boy is stuck. I drilled everything out almost to the original treads. I'm thinking can i cut re-cut threads and if so what size die do i use to cut the new threads? Or do i toss these carbs in the parts bin and take a chance on another set of carbs?

tw

Try a little heat on it to soften the thread sealer (heat gun, not a torch- no flame) then try the extractor while it is still warm.
Fish

Fish... did you hit the reply button twice or was this some sort of new issue? If it is, please post something in the ABOUT SITE issue for Stein... he should have some sort of timer that won't allow a double post... most message boards do...


As far as the thread lock thing. It probably isn't thread lock... probably the brass/aluminum have galled. This causes the thread to lock all by itself. LOTS of Keihin carbs I get in my shop have galled thread on the mixture screws for some reason and drilling the screws out is a PAIN. The heat/extractor tip will work about as well for galling as it will if someone used thread locker (geesh that would be dumb!). If you can't get the thread cleaned out, don't be surprised. I can't get many of these cleaned out using either a left hand drill bit or easy out... heat is the ONLY hope...

If you can't and drill the old screw to retap, I THINK the thread is 6mm x .75 pitch. I would DEFINITELY use a pitch gauge and measure the good mixture screw. Use a drill bit down from 1/4" as you will tend to open up the hole drilling more than you think. 5/32" is good to start and a hard drill bit sure helps. Titanium Nitride bits are OK but carbon steel are better. Using a real hard bit makes the hole less prone to expanding from wandering.

I'll give the heat one last try before i try retapping the threads. If both fail i guess i'll be searching ebay for a decent set of used carbs. I've seen these screws stuck before, but with a little effort and a good screw driver i can usually get it.

tw

Suggest you use a propane torch and get it hot enough so you see the thread lock start to bubble. You'll toast the O-ring but at this stage...

don't heat the whole carb body. You don't want mess up the shaft seals...

wiredgeorge wrote:

Fish... did you hit the reply button twice or was this some sort of new issue? If it is, please post something in the ABOUT SITE issue for Stein... he should have some sort of timer that won't allow a double post... most message boards do...

No When I post the reply, it takes me to the post that I just posted. Then I hit the back button and it automatically double post. The other sites that I frequent dont do this.
TW..- if you need a carb body U2U me, I may have one (you pay shipping cost only)
Anybody know where I could buy a tactical flashlight?
Fish

Fish Check your U2U.

Attached are the crabs i'm looking for.