Galled Main Jet Venturi

[Bengt_Phorqs]

First off, a really big thanks to Justin for taking the time yesterday to help me with this carb.  We (well he did) spent a couple of hours in his great machine shop out back of his house boring out the main jet venturi almost to the threads.    Here's a pic (I hope).  

Does anyone have any suggestions on the best way to finish this?  I plan on taking a needle file to make a vertical cut, then a second one, and hopefully extract the section.  I fear that I'm going to damage the aluminum threads though.

Barring the success of that, does anyone have a 32mm carb body they would like to sell?

[Lucky_Lou]

not getting the full picture ??
Lou

[montmil]

I believe Bing refers to the part as the Jet Holder Block, IIRC.

Needle jet fits in the top of the brass jet holder and then the combo is threaded into the carb body. Lastly, a washer and the main jet get screwed into the bottom portion of the jet holder.

Poor ol' Mike has some brass/aluminum corrosion that has pretty well permanently bonded the jet holder block into the carb body.  

At least he has some brisket to gnaw on while he sorts out a challenging issue.  [smiley=thumbup.gif]

Yo, Bengt. You can probably be successful with a small triangular machinist file and a Harbor Freight set of dental picks. A small vertical nick in the brass thread, 180 degrees apart, should not effect carb ops at all. Luck to ya! Keep a cold Shiner nearby.

Monte

[Bengt_Phorqs]

It's getting closer.  I've taken the dremel and a small grinding stone and very carefully at low speed open the ID of the main jet venturi (at least that's how it is styled on the BMW Micro Fiche, but what's in a name?)  It's almost paper thin but the grunge in the threads is very solid.  I'm off to Harbor Freight for some dental picks.  My old ice picks just aren't getting it.  Stay tuned kidz, more to follow....

Oh, and Monte, the brisket is Fantastic and I haven't even popped my first Shiner Bock.  Not to late to ride down and have a delicious sandwich. [smiley=2vrolijk_08.gif]

[Bengt_Phorqs]

Well, most of the crud is out and the dental picks worked fairly well.  I'm to the point now that I need to find the correct size tap and chase the threads.  Does anyone know the thread form for the main jet venturi, aka main jet holder?  It's 12 mm but not a 12 x 1.0, 12 x 1.25, or 12 x 1.50.  Armed with that information I'm sure I can order the tap from McMaster Carr.

[Flash]

I have a set of flat top 32mm apart, and I just went out and checked and mine are definitely 1.0.
I don't have a 12 x 1.0 die to test run the jet block through, but I have a pitch gauge that gave me that reading.
You should try heating the carb structure surrounding the piece, let it cool, and repeat the heat cool cycle a few times. The two metals expand at different rates, and sometimes that's enough to break the bond.
For future reference, when drilling out a stuck fastener, use a reverse drill bit, which operates counter-clockwise. This will encourage the stuck piece to back out while you drill it, as opposed to tightening it.
Best of luck.

[Bengt_Phorqs]

Flash, thanks for the readout.  I'll double check the 12 x 1.0 but it didn't seem to fit on my tap.  And FWIW, reverse drilling wasn't going to do any good.  That sucker was bonded in there tighter than the bark on a west Texas mesquite tree.

[montmil]

And, Bengt, the HB industrial-grade picks will work well getting the last strands of brisket outta your bridge work.  

I'm beginning to wonder if the PO had not "fixed" the female possibly stripped threads with something like JB Weld. You should not be having such a struggle now that there are only small bits remaining. Could be why your tap doesn't seem spot on.

Monte

[Bengt_Phorqs]

Well, I'm too young for bridgework like you guys that are on social security, but I'll keep your suggestion about the brisket picking in mind.  As for the tap, that was my mistake, after I spoke too soon I went back out and looked and I don't have a M12 x 1.0 tap.  I need to find one and so far the internet search has not shown much success.

JB Weld doesn't seem the likely culprit, it's just old varnished fuel that doesn't want to break up.  Anyhow, I'm ready to run the tap and that should chase the threads.  I hope! :-?

[Justin B.]

You'll find the necessary tap on this page...

http://www.msdiscount.com/columnar.aspx?cat_id=1173&session_id=377916153&category_site=STARTOOL

[Bengt_Phorqs]

Thanks Justin, looks like a good web site.  Just one caveat with these tool houses and that is they like to nick you for a $25 minimum order.

[Justin B.]

I wish I'd have known we'd need this as I just placed an order with 'em Saturday!  I suppose that maybe between the two of us we might be able to come up with enough stuff we can't live without to get to that magic number.

Too bad they don't have sand...

[montmil]

  Too bad they don't have sand...

I heard that!

[Justin B.]

Oh, Phorqs, Monte's awake!!