Ok. 1995 speedster w/ dual 657's and dual mikuni carbs on each. I beleive SBN38's. While getting ready to rebuild them I snapped the retaining screw that holds the pin for the needle valve spring arm. It was rusted, and broke pretty easily. You can imagine my frustration, especially since I was being uber careful. I am wondering if anyone has ever tried to drill out a screw from inside one of these carbs, and if so, should I use a standard bit? Im not sure they make a screw extractor that small.
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Mikuni carburetor broken internal screw.... any ideas???
- Thread starter WATERDAWG
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Dr Honda
Well-Known Member
If the screw broke because it's rusted to the body... then an extractor won't help. (normally) But, as you were saying... it's small.
I've drilled them out... but I put it in my big mill, and use 8% cobalt steel drills so they don't flex.
If you are going to try it... make sure you cut it flat... center punch it... and if possible... use a left hand drill. That way, the heat and friction may grab the screw, and run it out.
Last thing... when you disassemble these carbs... you have to use a hand impact screwdriver. If you don't... you will strip, or break the internal screws.
I've drilled them out... but I put it in my big mill, and use 8% cobalt steel drills so they don't flex.
If you are going to try it... make sure you cut it flat... center punch it... and if possible... use a left hand drill. That way, the heat and friction may grab the screw, and run it out.
Last thing... when you disassemble these carbs... you have to use a hand impact screwdriver. If you don't... you will strip, or break the internal screws.
Thanks for the quick reply Doc. I wish I had enough to cut, but it broke just below the surface. I can try punching it and left drilling it out, but I have little faith due to the size, and I will most likely only get one shot at it. I guess my next question would be.... anyone know where I can get a deal on a carburetor??? :banghead:
Hi go to www.osdparts.com good prices.
Dr Honda
Well-Known Member
Dr Honda
Well-Known Member
I have a 38mm body in ok shape. It's from a std set... so you will have to put your throttle and choke shaft in it. I just checked it, and all the ports are clear, and all the threaded parts are good. (you will want to give it a good cleaning though)
$25 shipped to you, and I'll even send a screw for the regulator pivot.
PM me if you want it.
$25 shipped to you, and I'll even send a screw for the regulator pivot.
PM me if you want it.
Update**
Thanks guys for your help. I managed to drill out the screw. Even though it was somewhat off-center, I picked up a slightly larger tap at the local hardware store. A 6-32 SAE tap is a wee bit bigger and worked out to be perfect. I replaced the screw with a flat head stainless, which I have used on all the internals that I have replaced. ( Someone please let me know if it's not good to use these on internal carb screws). very happy with the result, of course, no telling until I rebuild the port side and fire her up. Here are a couple of pics in case you're interested. Thanks again guys!
Thanks guys for your help. I managed to drill out the screw. Even though it was somewhat off-center, I picked up a slightly larger tap at the local hardware store. A 6-32 SAE tap is a wee bit bigger and worked out to be perfect. I replaced the screw with a flat head stainless, which I have used on all the internals that I have replaced. ( Someone please let me know if it's not good to use these on internal carb screws). very happy with the result, of course, no telling until I rebuild the port side and fire her up. Here are a couple of pics in case you're interested. Thanks again guys!
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