using a dremel to remove the butterfly screw threads.

[KA1J]

I'm having carb issues with the Maxim-X I picked up last week, I decided to break the rack and replace the throttle shaft seals. I didn't care to spend a long time carefully filing the peened over threads holding the butterfly to the shaft and wanted instead to use a carbide tip on my dremel in such a way as to not gouge the carb. Using a tip like this would take seconds but any slip and it would ruin the carb. I need a carb Chastity belt and one that's re-usable many times over.

What to do?

I had an idea and had to give it a try; How about making an epoxy barrier to protect the aluminum? Epoxy putty would be perfect, pliable, hardens fast and once hard would be like a rock barrier inside the ID of the carb. It would only need to be on the side the threads stick through on the throttle shaft and should be deep enough to be sure to protect anywhere inside if the dremel jumps off the threads.

Can't have the epoxy adhering to the carb or that would be a real problem so what to do? Oil! The epoxy will still harden even when soaked in oil and if I oil the output ID real well, there's nothing for the epoxy to cling to and if I press the epoxy thin and wide, it'll have the perfect shape to do what I want. I sprayed Kroil all around the inside figuring it will do a twofer by also helping to loosen the butterfly screws. { Important to use the bottom of the output so you don't push epoxy into the 4 tiny air tubes in the top part up above }.



After it's hardened then you push it out from the input side. I used a popsicle stick so as not scratch the aluminum. Note how it's more than 1/2 the diameter, it needs to be even less that 1/2, it needs to rest on the throttle shaft on both sides but be thin enough to not interfere with the carbide bit.



I used a cutting disk on the dremel to trim the ends perfectly. Be sure to make the edges rest flush with the throttle shaft, this will keep it thick enough at the edges. I mounted it so the middle was at the throttle shaft, giving me plenty of protection before & behind the shaft.

It fits perfectly!



It took maybe one minute to flatten both screw threads, it slides out easily and then slips in carb # 2 & so on.



Now I have a tool to use on any BS33 carb & I'll make one to fit the XJ11 as well with it's larger BS34 carbs. Ought to come in handy at a carb clinic too!

Cheers!

[DGXSER]

Very nice work!! I have only tried to pull those butterfly shafts out on a scrap set of carb bodies. After that experience I doubt I will try it on a set I want to use unless I am certain the seals are leaking. That is a very nice piece of work there!

[jetmechmarty]

Aren't those JIS screws? I have successfully backed them out. You just can't slip or it's over.

[KA1J]

DG - Thanks! Yeah, it works perfectly. I needed to soak these bodies overnight to completely clear out the blockages from sitting for so many years. I'm glad I changed the throttle shaft seals, they were as hard as toenails. Now the carbs are free of obstruction & look as new.

Marty - Yes they are JIS screws. I have a full JIS set & though I read these are JIS #2, they fit the JIS #1 screwdriver perfectly and the #2 is too large. Not sure what you're thinking of when you say "You can't slip or it's over". If you're talking about how to unscrew them, I've heard a battery powered impact gun works great if you put a block underneath the back of the shaft and first pound the screwdriver tip into the head of the screw and doing this, even munged screw heads come out...

Not having such an impact gun, what I did was to as you see, use Kroil which is a top of the line penetrating oil & squirted it on both sides of the screws. I let it sit overnight and the next day I seated the #1 firmly in the head and gave a slow, strong and downward rotation keeping the screwdriver in the plane of the screw and when I met firm resistance, I held it there and hit the end of the wrench with a 19mm wrench and then with that same downward and rotational pressure checked to see if the screw came loose. If it didn't immediately break free I repeated this but all the screws broke free within two whacks (most after the first whack). When I was able to move all 8 screws I knew all I needed to do was remove the threaded end and they would easily come out & then broke the rack free using an impact hammer. I didn't press down hard at all in a way that would have caused damage is I slipped.

[BA80]

I've taken several of these apart and put them back together and never had a problem. Automotive applications I've had to use this method though.

[jetmechmarty]

Marty - Yes they are JIS screws. I have a full JIS set & though I read these are JIS #2, they fit the JIS #1 screwdriver perfectly and the #2 is too large. Not sure what you're thinking of when you say "You can't slip or it's over".

I was referring to camming out of the screw head and damaging it, making it very difficult to remove.

[KA1J]

I was referring to camming out of the screw head and damaging it, making it very difficult to remove.

Ah, right. I'd hate to have a head come off or become unusable. I'm not sure how I'd deal with that. I can see a solution but don't have the equipment to do it.

I've come to appreciate Kroil as the ultimate penetrating oil and when I have used it, so far 100% of the things I needed to be freed, came free with it. I do have a junk set of carbs I was sold before I understood what was junk with these bikes. I bought a set of junk carbs for a high price and I ought to see if I can undo those butterfly screws... If I can, I have a lock on the technique...

[mack]

I've removed

the butterfly's on all my carbs (eight sets) to clean them. I use an electrician philips screw driver. If one is difficult then I drill a small hole in the center of the philips slot and stick a square head screw driver in it and turn it out easy as pie. The replacement screws are dirt cheap and I use the blue lock tight when replacing them.

[DAVINCI]

Plain old impact driver works, back up the shaft with a deep socket