Engine: 2.1 Carb B21A: Pierburg strip and clean part 1

[Bob 1967]

Pierburg started acting up and I had sourced a Stromberg fairly cheap .
I was going to do a swap , but as can be seen...


It's the mirror (fuel feed and throttle are on opposite side) D'oh!
So that's not going to work (you certainly get what you pay for!)
Okay ,rebuild kit ordered I gave the outside a clean .
First off the Damper and plastic cap followed by the Pot cover



The throttle slide was manky with carbon/soot and the Needle was covered in green crud ( I would find more later)

The chamber wasn't much better.


Float chamber base remove screws and remove


More crud, it's a wonder it ran at all


Remove the clip centre of pic ( it comes out with no effort ,just fingers)


And releases the float bowl, clip is at top left beside float

With float removed chamber has green crud deposit (possibly from moisture/or condensation from breather ??)


I didn't want to strip any further until I had the kit in hand ,so on with the prep.


If you look closely as I did you will see lines that look like cracks ,but they are actually bad casting marks.
They were also apparent in the chamber top, which wouldn't be good for the diaphragm (It wasn't ,it had a similar pattern and was perishing)




all cleaning done with a non Dremel with a wire cup brush.
I am tempted to grind the bad casting ridges to a smooth finish.

More to follow.....
Bob

[Bob 1967]

The Diaphragm has a locating lug on its outer edge that sits in a corresponding slot in the carburettor body , make a note of its orientation in relation to the openings in the Piston and the Jet Needle .





The top of the diaphragm has four Lugs and the Piston has four cut outs so it can go in four positions ,but only one is correct. (See second picture in previous post for top view.)

The intake manifold was spotless , probably due to the over rich fuel mixture.

Bob

[Bob 1967]

The top of the diaphragm has four Lugs and the Piston has four cut outs so it can go in four positions ,but only one is correct. (See second picture in previous post for top view.)

This as I found out is incorrect ,the diaphragm has not got four lugs .
They are on the plastic retainer that holds the diaphragm to the piston.
Bob

[Othen]

Originally Posted by Bob 1967

The top of the diaphragm has four Lugs and the Piston has four cut outs so it can go in four positions ,but only one is correct. (See second picture in previous post for top view.)

This as I found out is incorrect ,the diaphragm has not got four lugs .
They are on the plastic retainer that holds the diaphragm to the piston.
Bob

Bob,
From memory: the diaphragm has a small tab which locates in a slot so it can only fit in one position.
Alan

[Bob 1967]

Originally Posted by Othen

Bob,
From memory: the diaphragm has a small tab which locates in a slot so it can only fit in one position.
Alan

Yes Alan ,as mentioned in #2

"The Diaphragm has a locating lug on its outer edge that sits in a corresponding slot in the carburettor body , make a note of its orientation in relation to the openings in the Piston and the Jet Needle ."

I have the green carb book already as a PDF along with a similar PDF for Saab applications ,but information is vague at best and there is no info on strip down or needle removal.

If you put Pierberg 175cd into any search engine , about 95 % of results come back are Stromberg.
They are as similar as a VW Beetle and a Tatra 97 .

I have worked on Keihan slide carburettors (simplest of designs but very effective) and Constant Velocity easy to set up,balance and tune (even a bank of 4)
Bing CVs on a BMW twin all were very effective at what they did and again easy to fine tune .
Why should a single carb be so finicky ?


I just find with so many variables ; hot air (warm start pre heated from exhaust )from throttle body at air intake (below the battery next to radiator), dirty air recycled from rocker cover both through the air filter housing (round type) and directly through a solenoid into the inlet manifold .Also there is the vacuum effect from the distributor and finaly the main air intake itself: there are just too many things that can affect the running .
A bit of a headache really.

I wonder if I made my own manifold could I fit a bank of 4 x 34mm CV carbs
or maybe a flux capacitor !!

I think the crud may have been caused by ATF damping fluid passing a seal and making its way into the float bowl .

Bob

[Othen]

Originally Posted by Bob 1967

I just find with so many variables ; hot air (warm start pre heated from exhaust )from throttle body at air intake (below the battery next to radiator), dirty air recycled from rocker cover both through the air filter housing (round type) and directly through a solenoid into the inlet manifold .Also there is the vacuum effect from the distributor and finaly the main air intake itself: there are just too many things that can affect the running .
A bit of a headache really.

I wonder if I made my own manifold could I fit a bank of 4 x 34mm CV carbs
or maybe a flux capacitor !!

I think the crud may have been caused by ATF damping fluid passing a seal and making its way into the float bowl .

Bob

I recall that LS found a manufacturer of inlet manifolds that allowed twin Weber carburettors to be fitted to a B21a - it is one of those things I might just get round to doing to the RB one day (but then does one stop - flux capacitor?).

The settings for Pierburg on the RB were a long way from where they should have been when I bought the motor car; I followed the set up routine in the green book and had it running quite well in about half a day. I also got a local MoT station to check the CO output, which allowed me to get the mixture screw adjusted correctly, after that it was much easier.

The Pierburg is not a very sophisticated instrument, I notice it varies quite a bit with the environment (especially temperature), but perhaps I have just got used to fuel injection on cars - although all my bikes have carburettors (CV and flat slide Keihins variously).

Good thread about cleaning the carburettor.

Alan

[Bob 1967]

Just to clarify, I changed only the diaphragm.
Everything else was fine after cleaning.

[Othen]

Originally Posted by Bob 1967

Just to clarify, I changed only the diaphragm.
Everything else was fine after cleaning.

Good guide Bob,

This, a diaphragm and some carburettor cleaner will be all Kelton needs to sort out the RB. Total cost a tenner.

Alan

[wisty]

Do I need to take the carb off to do this? If so, are they easy enough to take off? I'm thinking I should try cleaning it without taking it off first, get an idea how dirty it is? I ordered a diaphragm a few days ago so I can replace that at the same time. I'll hold off ordering the rebuild kit. Thanks to you both.

Kelton

[Bob 1967]

Alan would know how to remove the carb, it is a different set up to mine....
Shows the engine bay. Took the liberty of using Alans pic from his thread.



3 hoses to be removed(red), The big jubilee clip for the air intake.(blue)
The throttle cable(or the linkage Alan?) and choke.(green)
Not sure how carb is attached to the manifold.
Disassembly of the carb in situ is risky, bits could fall and be lost forever.
Take pics and note where things were.