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Old 02-22-2013, 04:16 PM   #1
ironjack63 OP
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Pissed idle mixture screw tech help

I am in desparate need of some experience. I took the second carb off of my recently acquired '81 R100RT to clean it and rebuild it like the first one. I took out the mixture screw only to see that some previous owner had broken off the slender tip of this screw and the piece is still stuck in the carb body. Anyone know how to get this broken piece out without screwing up the carb body? I really don't want to spring for a new carb for a tiny piece of brass. All advice will be greatly appreciated.
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Old 02-22-2013, 04:57 PM   #2
chollo9
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Compressed air is the first thing I'd try. Then I'd try it along with come aerosol contact or carb cleaner.

If that doesn't work, a guitar string inserted carefully through the bleed hole might push it out. I'd be really careful with this though, you don't want to get it stuck alongside the taper.
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Old 02-22-2013, 05:00 PM   #3
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Try compressed air.

I'd never heard of anything like this happening before - it's one of those things you'll just have to stare at it and eventually the right idea will come.

I believe those screws are steel, not brass. Perhaps there's a small neodymium magnet that can get in close enough to draw it out. Or possibly a piece of wire could be bent or held in pliers and apply force from the throat side. Squirt carb cleaner from the back side to possibly loosen it.

This isn't something we commonly run into, so it's going to require getting inventive and coming up with a bright idea. It'll come out, just don't start beating on it!
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Old 02-22-2013, 05:06 PM   #4
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Or you could beat on it.
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Old 02-22-2013, 05:10 PM   #5
Kai Ju
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If he screwed it in tight enough to break it, compressed air won't do this.
Take a right angle pic and push on the broken tip coming from the throttle bore side.
The bleed hole is directly in front of the butterfly valve.



This should work because the tip on the bings is rather fat compared to a Mikuni or other Japanese carbs.

Good luck.
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Old 02-22-2013, 05:50 PM   #6
disston
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The needles are steel.

I suspect that you have a dented or broken off tip but it is not in the idle passage. Use a magnifying glass and see if you can see it? Use compressed air. If there is a piece of the tip in there you may be screwed.

Another piece of advice. If you can still use this carb and are going to buy another idles screw, buy two. Replace carb parts in pairs, as a rule. You may break this rule for really expensive parts like slides or carb bodies but if you ever get there you'll probably be looking for a used pair instead anyway.
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Old 02-22-2013, 06:09 PM   #7
ironjack63 OP
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The end is indeed stuck. I don't believe compress air will do anything, as I have already tried a large straight pin bent into a 90 and clamped into vice grips. This did nothing, so I am stumped. The bike has been sitting for almost 7 years, so I am guessing it was run up in their forcefully and over time the dissimilar metal corrosion has really stuck this thing in tight.
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Old 02-22-2013, 06:40 PM   #8
Kt-88
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Quote:
Originally Posted by ironjack63 View Post
The end is indeed stuck. I don't believe compress air will do anything, as I have already tried a large straight pin bent into a 90 and clamped into vice grips. This did nothing, so I am stumped. The bike has been sitting for almost 7 years, so I am guessing it was run up in their forcefully and over time the dissimilar metal corrosion has really stuck this thing in tight.
This was the case with my r90. The tip of the screw was sheared and I ended up buying a new carb body. Which ones do you have? If I have an extra it's yours.
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Old 02-22-2013, 06:56 PM   #9
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carb

Try putting the body in boiling water then use the pic. I have done this to loosen stuck screws and worked good.
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Old 02-22-2013, 06:59 PM   #10
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Quote:
Originally Posted by ironjack63 View Post
The end is indeed stuck. I don't believe compress air will do anything, as I have already tried a large straight pin bent into a 90 and clamped into vice grips. This did nothing, so I am stumped. The bike has been sitting for almost 7 years, so I am guessing it was run up in their forcefully and over time the dissimilar metal corrosion has really stuck this thing in tight.
if above is truly the case and you've tried everything. including compressed air, pushing from behind, boiling water, etc and you are ready to scrap carb.

this is a last ditch attempt at fixing with a chance of damaging seat.

1. locate a pin drill bit set like below
2. use a pin vise to hold tiny drill bit
3. use jeweler's magnifier lens hood, you must see tiny details.
4. carefully match drill bit size to undamaged seat on sister carb.
5. very .. very .. carefully drill out broken tip. you may want to start with a smaller size bit, then finish with matching size. depending on if you are successful at starting bit in center of broken tip.

... here's what to do if you screwed up seat by drilling ... carefully degrease/clean damaged seat. then apply a dab of JB's Weld or your favorite gas resistant epoxy. allow to set ... then drill new hole with correct size drill bit matched to sister carb. take extra care not to bottom adjustment screw too tight before backing out.

good luck ... above may still not work, but it's worth a try on a carb to be scrapped. who knows... you may get lucky??


_cy_ screwed with this post 02-22-2013 at 07:11 PM
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Old 02-22-2013, 08:19 PM   #11
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212 degrees isn't very hot. I would use some mapp gas before I did anything drastic.
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Old 02-22-2013, 09:09 PM   #12
ironjack63 OP
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Quote:
Originally Posted by Kt-88 View Post
This was the case with my r90. The tip of the screw was sheared and I ended up buying a new carb body. Which ones do you have? If I have an extra it's yours.
I have the 40mm Bing CV.
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Old 02-22-2013, 09:12 PM   #13
ironjack63 OP
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One more item relating to this request for help, if I should succeed and get this broken tip out, where in the world can I find a new mixture screw?
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Old 02-22-2013, 10:49 PM   #14
Kt-88
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I bought mine from BMW hucky's I think.
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Old 02-22-2013, 11:36 PM   #15
disston
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Carb parts are carried by Airhead friendly dealers and Hucky's, http://www.bmwhucky.com/ I don't know how far away you might be from an Airhead friendly dealer but if there is a dealer near you then asking for internal carb parts would reveal their attitude towards the older bikes. Hucky's is a favorite place to get parts. You should call to order after talking to Hans on the phone and he will explain his way of dealing.

There are many other on line parts sources. There is a Web site for the Bing people them selves. A funny thing is that we almost never order parts from them, except for a few things that nobody else has, the parts will be cheaper at a dealer's.

Here is another great place to get parts. Ted Porter doesn't have much of an online presents but he will have the parts, http://www.beemershop.com/.

Another great on line source, the place I get to go to personally, is Bob's, http://www.bobsbmw.com/

All the places I have mentioned so far you should order over the phone.Their web pages may help finding the part numbers you need but I think all of these sources work best with phone orders. Most of them don't work at all by using just on line.
One place that you can order parts on line and not have to use the phone at all is Max's BMW, http://www.maxbmwmotorcycles.com/ The Max site is a favorite for using the parts fisch as reference anytime.

There are others.
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