Modifying a 34 Pict 3 for semi auto use

[volkenstein]

Sportsfans,
               Some of us here have gone over this a few times in the tech section but I thought doing it with some piccies would be good and would save people some time.

Why do this?

Well, when an autostick carby get's replaced more than a few people have slapped a manual carby on. Unfortunately it's a day late and a dollar short for functioning well on an autostick car as a manual carby lacks the necessary vacuum port for the CV feed. The most common symptom is "slamming" into gear when you release the shifter.

The Brosol H30/31 Pict does in fact have the correct port, but a woeful vacuum advance signal.

But to business, a 34 Pict 3 manual carby (this one is off a 1600 Type 2).

I had a piece of 10mm MDF lying around so I drilled two carby stud holes in it so I could bolt the carby to it and have acres of fun without mangling the butter soft carby. Whacked it into a drill press and put some tape on a 4mm drill about ten millimetres from the drill tip. Just a visual cue to stop it when the initial hole is deep enough.



You can see which port I'm drilling into, which is the one to the RIGHT of the coin sized plug.

[volkenstein]

Righty ho,
             Out with the 4mm and in with a 2mm bit and this time drilling all the way through into the venturi.



Here's another shot of what it looks like in the venturi. Just de-burr it to clean up any ragged bits left from drilling.

[volkenstein]

Almost done,
                 Here's a shot with the bits I used to finish it off. Loctite 609, a 15mm-20mm length of 4mm OD brass tube and not shown is a 75mm nail to pein the carby body around the tube.



Coat the tube OD with the Loctite 609, press it into your newly made spigot recess and then using the 75mm nail pein the spigot boss so it grips the tubing piece and you're ready for action.

Couple of things to mention here. You DON'T need the heavy duty tools or whatever. A simple electric drill, a steady hand, care (the carby body is SOFT) and some glue (Araldite or whatnot) is really all you need to do this.

Mike (Bookwus) has used a 3/16 and 9/64 drill bit combo to acheive the same results. Yes, it's larger, but it works just as well. You could easily go 5/32 and 5/64 (or 3/32) but it's far easier to figure out what drills you need if you have the tube. Speaking of that, either a hobby store or a metal shop generally have some small OD tube racks.

In the stock A-S 34 Pict 3, the tube has a 1.5mm restriction ("jet") but the hole in the venturi is 2mm and I've measured both on my unmolested 34 Pict 3. It doesn't matter that much, you can tune the CV to compensate if necessary. Just FYI...


Enjoy
Volkenstein

PS. I'll be adding another favourite mod to this topic as this carby is undergoing some rescue work.

[Bookwus]

Hiya Sean,

An excellent subject for Step-by-Step!

.........but it's far easier to figure out what drills you need if you have the tube.......

Actually, when I determined the bits to use for this job I fit the 3/16 to the hole in the carburetor boss.  It was close to a perfect fit and it worked very well for reaming out the existing hole and leaving a conical end cut into the carb body.  That end cut allowed me to easily center the 9/64 for completing the passage into the venturi.

And, not to sidetrack this tutorial, but in all the carousing around I've done in tool stores here in the States, I have yet to find drill bits in metric sizing.  Maybe I'm just looking in the wrong places.

In any event, good one Sean!

[volkenstein]

Mike,
      Hard to find metric drill bits? That's a real shock to hear! I guess since we (Aus) changed over to use metric way back in '72 odd I tend to take for granted the fact places here stock Imperial and Metric as a matter of course.


Regards
Sean

[volkenstein]

All,
   So the next thing for this carby is to ensure the fuel inlet fitting has no chance of coming out. In a bizarre twist, this fitting was actually in there damn tight....unfortunately I fixed that .

Anyway, here is the shot :



What I've done here (lower left of piccie) is make up from a piece of 3/8 (or 10mm) hex a new fuel fitting with a 5/16 UNF thread on one end. The carby has had the original fuel fitting taken out and a 1/4 drill run down it and there in the pic you can see the 5/16 UNF tap (started in the drill press then finished off by hand). A sundry item is that aluminium washer I made up. .8mm thick, 8mm ID x 10.4 OD.

After much cleaning and making sure there is no loose swarf and de-burring the threads etc I seal it up with some Loctite master pipe sealant and lock the fitting in tight.

The finished product :



Lot's of people use safety wire on the fuel line clamp and/or pein the stock fitting in there which is fine, I just prefer this method simply because I have the tools 'n' stuff.

Volkenstein

[Bookwus]

Hiya Sean,

Yep, this is the sort of thing I do...............



because I don't have the tools 'n' stuff.

Lucky guy!

And I'm still on the lookout for metric drill bits.

[volkenstein]

Mike,
      You're in Oregon IIRC? Have you tried General Tool & Supply Co - ph 503 226 3411 or 800-783-3411?

Regards
Sean

[volkenstein]

All,
    The vacuum spigot has been done, fuel inlet mods shown (nice piccie Mike!) which leaves righting other wrongs with this carb. So the other nasty things with this carb is that it had been 009-ised as per:



Main jet of a whopping 140 size and (thankfully for me) an aluminium pop-rivet in the throttle plate hole. Also the nasty matter of the volume control screw (the small s***ty one) being sheared off down by the o-ring.

The Main jet was pretty easy, although I wanted to prove a theory. Mikuni bike carb jets are supposed to fit. Sure as eggs there are 4 different types. 2 Hex fitting and 2 round. The N600 series are the ones you need. Described as "large head, screwdriver slotted". Fitted beautifully (eyeballed same length and thread is the same as a Solex). I did however wind up ordering from a specialist supplier as bike shops round here wanted $20US . Makes more sense just to go to a VW place and get a Solex one, around $10US plus postage .

The aluminium pop rivet came out after twisting a 8mm bit by hand on it for a while and tapping it through. Woe to me, of course it left hundreds of fine aluminium shavings everywhere so yet another dousing with carb cleaner and another compressed air session.

The nasty volume control screw next installment once I prep a photie or two.

Enjoy
Volkenstein

[Bookwus]

Hiya Sean,

........You're in Oregon IIRC? Have you tried General Tool & Supply Co.........

You're good!  How'd you run into those guys?

They're not all that far away from me.  I'll have to wander on down and give 'em a shot.  Probably won't be for a few days though.  We're right in the middle of, for us, one heckuva blizzard.  We're all snowed in with many of the local road closed down.

OK by me.  It gives me some time to work on my brand new Bus engine which blew up a few days ago.

[volkenstein]

Mike,
      I couldn't believe that metric stuff would be hard to find, so google came to the rescue. Hmm..I keep forgetting while we are preparing to fry eggs on the footpath, it's positively freezing "way up norf".

brand new Bus engine which blew up a few days ago

Ouuccchhhhh. That has to hurt badly, especially this time of year .


Regards
Sean

[volkenstein]

All,
   So on with dark doings in the shed. The idle screw had sheared off as I mentioned previously and after mounting it in that MDF bracket and resting the body on the vice I tried running a 3mm bit down there.
Utterly no dice at all, the drill would step off and try drilling where I didn't want. Ebay came to the rescue with a 3mm end-mill for a ludicrous bargain price.

Back into the drill press and going very carefully I was gratified to see swarf appearing, so ran it down to the preset stop. It was still a little too short for my #0 extractor so out came the 2mm drill bit and I went "just that little bit further"  and can you guess?? Yep, the needle seperated from the screw body. Anyway, the #1 extractor went in and with some judicious twisting the screw let go and it backed out. I think it took about 1 thread of pot metal out but a visual look confirmed that the carby thread was OK, just some rubbish left in the screw thread. Oh, and that needle jammed refusing to budge .

A drill and self tapping screw later had the plug popped out and the needle in my hand. I ran a 3mm bit through my now hollow screw (that german steel is GOOD!) and hit the lathe to make up a full length needle. Brazed it all together and let it sit in vinegar for a night. Next morning, the threads were gleaming and not a skerrick of flux slag to be seen. A bit of dressing work and here we are :



The arrow is pointing to the replacement plug I made up and loctited & peined in there. I made the screw longer so I could see the damn thing and not have to fish inside the hole for the slot. Also it would stop a repeat occurrence and you can grip the damn thing with pliers should the need arise.

Just got my brass bushings from the UK today, but I'll save them. This ones shaft isn't sloppy so I'll let the plastic ones wear out.

Other things wrong? Accelerator pump spring was not correct and made a mess of the whole linkage. I had a spare so whipped it on. Also fixed up the mal adjusted choke and freed up the plate. Plenty of Decaf ( how the mighty have fallen) and ciggies on this little effort thus far...

Enjoy
Volkenstein

[bowlingbrad]

In the stock A-S 34 Pict 3, the tube has a 1.5mm restriction ("jet") but the hole in the venturi is 2mm and I've measured both on my unmolested 34 Pict 3. It doesn't matter that much, you can tune the CV to compensate if necessary. Just FYI...

Sean,
If I have a 1.5mm bit, should I use it to drill the final hole?  Should I go in halfway with 2mm, then finish with 1.5mm?  Does it really matter??

Brad

[volkenstein]

Brad,
      Just me being a stickler. 2mm (or imperial equivalet) will be fine. It's up to you. You can still fine tune your CV to suit via the adjuster screw.

Regards
Sean

[Bookwus]

Hiya Brad,

Just adding in that using the two different sizes of drills does make for a "shoulder stop" in the hole.  That helps you bottom out the brass vacuum port when you tap it in.  Doing it that way mimics the process Solex originally used in making the AS specific carburetor.