Broken mixture screw....

[R65Singh]

Hello all....While trying to find out the erratic running of one cylinder and unable to run steady at idle,  I finally took apart the carb and noticed that the mixture screw's tip is broken inside the carb body.  It is stuck solid inside and is at awkward place to push it back out.  Looks like the PO overtightened the mixture screw and that made it to break.  This bike is full of surprises.  Please provide any ideas/methods to take it out?  

[Rob Valdez 79 R65]

I just recently read about reverse-drill bits, and using one of those, smaller than the thread diameter, will sometimes bring it out as it drills out the center and relieves the stress.

Gotta be careful!


edit:  Yeah, there it is!  This thread is about a stuck main jet:
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1252340771/5#5

[montmil]

Doubtful if there's a reverse twist drill bit available that small. The pucker factor of destroying the carb body would likely hit a 10+.

Singh, is it just the pointy end broken off or is there some threaded shank left in the carb body?

Monte

[Flash]

I discovered a very similar problem recently on my previously neglected airhead. The tip of the mixture screws were corroded, an part of one stayed in the orifice when I removed the screw, along with the crud from old fuel.
I have a set of "jet drills", which are exactly that, a collection of tiny drills that come packed in the screw top handle of the hand drill which looks like a oversized pencil. I have never used them to drill metal, but when a jet or orifice is plugged, I select a drill that is smaller and use it to push through so the carb cleaner can get in and start doing its job.
I also have what I believe is a welding tip cleaning kit, which has very small rods that fit a lot of small passages and can be used in the same fashion. Here's a link that shows a photo of what the author calls a Honda jet cleaning tool that looks just like my welding tip cleaner.

http://home.earthlink.net/~motorstuff/tools02.html

and here's a link to an ebay picture of the pencil type I use mostly.
http://cgi.ebay.ph/ws/eBayISAPI.dll?ViewItem&item=270429954365

Keep soaking the orifice with carb cleaner, and do not enlarge the hole at all. Once you get an opening in the blockage, carb cleaner will do the rest.  
Good luck.

[Bob_Roller]

If things get beyond your capabilities, or comfort zone, Bing Agency in Kansas, offers services to remove stuck jets, and needles .


http://bingcarburetor.com/services.html  

They'll quote you a price before shipping it to them, they aren't cheap, but neither is replacing a carb body .

[R65Singh]

Doubtful if there's a reverse twist drill bit available that small. The pucker factor of destroying the carb body would likely hit a 10+.

Singh, is it just the pointy end broken off or is there some threaded shank left in the carb body?

Monte


It is just the tip that is broken inside.  The problem is that the orifice is not accessible for a direct hit from behind otherwise it will be easy to pop it back out.  I tried using sewing needles held in a vice grip but the brass portion of the tip is just too brittle and keeps breaking away.  I will just keep going at it until i get it all out.  I will try the carb cleaner too...i guess nothing will hurt now...probably it is already ruined by now.  Thanks for the help guys... will keep u guys posted.

[Bengt_Phorqs]

Singh, I'm in the middle of a repair to my main jet holder/venturi.  Just waiting on the M12x1.0 tap to get here so I can finish it off.  A word to the wise, send it to Bing to fix it!  If I'd known about that I would have done the same thing.  They are experts at that sort of thing.

[Justin B.]

C'mon Phorqs, it's been a great learning experience!

[montmil]

Yo, Bengt... Ya want some cheese with that whine?

Don't go all soft on us, man. Keep after it. Satisfaction of meeting and conquering the challenge and all that stuff.  

Monte

[Bengt_Phorqs]

Hey guys, I'm not whining or crying.  We all know there's no crying with R65's! It was an FLE and I couldn't have done it without Justin's fine mechanical abilities.  And this morning the tap came so I had the threads chased and the carb has been reassembled and ready to install on the bike.  (BTW Justin, if that ever comes up again be sure to mount the carb body to a piece of plate before putting it in the vise.  Had to gently tap the top back onto the body.)

No really, I'm just trying to help Singh out if he has some doubts about his ability.  Try to find a used carb that's affordable.  Go ahead, I dare ya to.  But his issue sounds fairly difficult the way he described it.  Plus he still has the spring below the needle to extract.  I'm just saying it could be really tricky.

[Semper Gumby]

I'm a wuss too - I would send it to Bing in Kansas.  

Cave aged Gruierre is pretty good cheese or a nice Stilton and some Port to sip on while waiting for the carb to come back.  Just not too much Port please!  

[R65Singh]

Got the sucker out!!!  Yes it took a while and trying lots of this and that but finally it came out.  I used the "push pin trick" method using a fine screw driver bit instead.  Please have  a look at the attached picture to get an idea...it might help someone else in a similar situation.  I  used the precision screw driver bit (Push pin was too weak) and it came right out with a little effort.  The bike is breathing properly now!!!!!!
Thanks to all of you as well.

[Semper Gumby]

Cool.

Now for some cheeeeese (grommet).  

[montmil]

Those sure don't look like Bing carburetors to my eyes. Did I miss something in this thread? What BMW are these pots fitted to, anyway?

Monte

[Justin B.]

Crap, Phorqs, I wuz more afraid of cracking something!  I had no idea it might get squeezed in.  Definitely needs to be bolted down to a plate...