Zenith Carbs

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G

Graham G

Guest
Brother got his IIa up and running today, however he tells me that its
running like a bag of spanners!! He says that it ticks over fine, but under
acceleration it misses and chuffs out black smoke. Has turned the mixture
screw right in, and it will continue to run and accelerate with black smoke.
Economy diaphram has a small tear in it, is this likely to be the cause?? He
also seems to think ther is excessive wear around the hole through which the
shaft holding the flutter valve sits (apparently petrol comes out rount
here, but he thinks its a result of the huge amounts of fuel being dumped
into the system).

Should he get a repair kit? Is it something he's missing, or shoud he just
throw it in the hedge and buy a new one?

Any help is appreciated as he is baffled ATM.

Cheers

--
Graham

101 GS
101 Rad Bod


 
On Thu, 15 Dec 2005 19:35:51 -0000, "Graham G" <[email protected]>
wrote:

>Brother got his IIa up and running today, however he tells me that its
>running like a bag of spanners!! He says that it ticks over fine, but under
>acceleration it misses and chuffs out black smoke. Has turned the mixture
>screw right in, and it will continue to run and accelerate with black smoke.
>Economy diaphram has a small tear in it, is this likely to be the cause?? He
>also seems to think ther is excessive wear around the hole through which the
>shaft holding the flutter valve sits (apparently petrol comes out rount
>here, but he thinks its a result of the huge amounts of fuel being dumped
>into the system).
>
>Should he get a repair kit? Is it something he's missing, or shoud he just
>throw it in the hedge and buy a new one?
>
>Any help is appreciated as he is baffled ATM.
>

I had a lotta trouble with a Zenith/Stromberg carb on my IIa, despite
a rebuild with an overhaul kit, it still did strange things. I
replaced it with a brand new Weber, not had a single problem since.

Apparently they can have problems with warped carb bodies, something
to do with problems during casting.

Alex
 
....and Alex spake unto the tribes of Usenet, saying...


> On Thu, 15 Dec 2005 19:35:51 -0000, "Graham G" <[email protected]>
> wrote:
>
>> Brother got his IIa up and running today, however he tells me that
>> its running like a bag of spanners!! He says that it ticks over
>> fine, but under acceleration it misses and chuffs out black smoke.
>> Has turned the mixture screw right in, and it will continue to run
>> and accelerate with black smoke. Economy diaphram has a small tear
>> in it, is this likely to be the cause?? He also seems to think ther
>> is excessive wear around the hole through which the shaft holding
>> the flutter valve sits (apparently petrol comes out rount here, but
>> he thinks its a result of the huge amounts of fuel being dumped into
>> the system).
>>
>> Should he get a repair kit? Is it something he's missing, or shoud
>> he just throw it in the hedge and buy a new one?
>>
>> Any help is appreciated as he is baffled ATM.
>>
>
> I had a lotta trouble with a Zenith/Stromberg carb on my IIa, despite
> a rebuild with an overhaul kit, it still did strange things. I
> replaced it with a brand new Weber, not had a single problem since.
>
> Apparently they can have problems with warped carb bodies, something
> to do with problems during casting.
>
> Alex

The original Zenith on the 2a was well knackered, so I replaced with a
"Zenith type" (ie pattern) carb from Cra/Paddocks. It lasted a few months,
by which time it was so warped it would hardly run at all. The gap between
the lid and body on the front edge was over 1mm in the centre. Flatting the
mating surfaces on fine emery on a glass plate helped but didn't cure it.
Alex is right - it's something to do with the heat-treating during
manufacture, and there are a lot with this problem AIUI. It would not idle
evenly, even when set to idle at >1000rpm, ran extremely rich, and turning
the mixture screw in and out made no difference. I bit the bullet and got a
new genuine Zenith (now being manufactured by Burlen www.burlen.co.uk). Bit
pricey, but runs like a dream now.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)


 
Richard Brookman wrote:
>I bit the bullet and got a
> new genuine Zenith (now being manufactured by Burlen www.burlen.co.uk). Bit
> pricey, but runs like a dream now.
>

Could I ask roughly how pricey, looking on the website it says price = ask.

Tia
--
scruttocks
k12rs r80g/s sIIa
 
....and scruttocks spake unto the tribes of Usenet, saying...


> Richard Brookman wrote:
>> I bit the bullet and got a
>> new genuine Zenith (now being manufactured by Burlen
>> www.burlen.co.uk). Bit pricey, but runs like a dream now.
>>
>
> Could I ask roughly how pricey, looking on the website it says price
> = ask.
> Tia

Can't remember exactly, but it was a good bit over a ton - about 120 plus
the usual, I think. Give 'em a ring - they were very helpful to me.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)


 
Richard Brookman wrote:

> ...and scruttocks spake unto the tribes of Usenet, saying...
>
>
>
>>Richard Brookman wrote:
>>
>>>I bit the bullet and got a
>>>new genuine Zenith (now being manufactured by Burlen
>>>www.burlen.co.uk). Bit pricey, but runs like a dream now.
>>>
>>
>>Could I ask roughly how pricey, looking on the website it says price
>>= ask.
>>Tia
>
>
> Can't remember exactly, but it was a good bit over a ton - about 120 plus
> the usual, I think. Give 'em a ring - they were very helpful to me.
>


Thanks, I've got a fair bit of rust to exorcise before I can start
putting the shiny bits on, I can feel one coming on in the spring though
(hopefully).

--
scruttocks
k12rs r80g/s sIIa
 
....and scruttocks spake unto the tribes of Usenet, saying...


> Thanks, I've got a fair bit of rust to exorcise before I can start
> putting the shiny bits on, I can feel one coming on in the spring
> though (hopefully).

I didn't regret it...

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)


 
Graham G came up with the following;:

> Should he get a repair kit? Is it something he's missing, or shoud he just
> throw it in the hedge and buy a new one?

As Alex and Richard have said, a replacement 'other make' carb is a very
worthwhile investment. My S3 never ran properly with a zenith, but did with
a weber.

there are a few things you can do, as you suggest, the repair kit might
work, the flatting of mating surfaces might work, a damn good clean of the
petrol pipes, tank, sedimenter and carb might also help, as would checking
that air can also get in. A screwed air filter might also make one think it
could be the carb when it isn't ... ;)

--
Paul ...
(8(|) Homer Rules ..... Doh !!!

 
On Friday, in article <[email protected]>
[email protected] "Paul - xxx" wrote:

> Graham G came up with the following;:
>
> > Should he get a repair kit? Is it something he's missing, or shoud he just
> > throw it in the hedge and buy a new one?
>
> As Alex and Richard have said, a replacement 'other make' carb is a very
> worthwhile investment. My S3 never ran properly with a zenith, but did with
> a weber.
>
> there are a few things you can do, as you suggest, the repair kit might
> work, the flatting of mating surfaces might work, a damn good clean of the
> petrol pipes, tank, sedimenter and carb might also help, as would checking
> that air can also get in. A screwed air filter might also make one think it
> could be the carb when it isn't ... ;)

The oil-bath air filter is pretty free-flowing, though it's worth
cleaning out. I've had the semi-flexible air-hose on a diesel suffer an
internal collapse, which is serious black-smoke time.

--
David G. Bell -- SF Fan, Filker, and Punslinger.

"I am Number Two," said Penfold. "You are Number Six."
 
"David G. Bell" came up with the following;:
> On Friday, in article <[email protected]>
> [email protected] "Paul - xxx" wrote:
>
>> Graham G came up with the following;:
>>
>>> Should he get a repair kit? Is it something he's missing, or shoud he
>>> just throw it in the hedge and buy a new one?
>>
>> As Alex and Richard have said, a replacement 'other make' carb is a very
>> worthwhile investment. My S3 never ran properly with a zenith, but did
>> with a weber.
>>
>> there are a few things you can do, as you suggest, the repair kit might
>> work, the flatting of mating surfaces might work, a damn good clean of
>> the petrol pipes, tank, sedimenter and carb might also help, as would
>> checking that air can also get in. A screwed air filter might also make
>> one think it could be the carb when it isn't ... ;)
>
> The oil-bath air filter is pretty free-flowing,

Unless, of course as we found out, some nerk leaves their oily rags inside
the bloody thing. ;)

> though it's worth
> cleaning out. I've had the semi-flexible air-hose on a diesel suffer an
> internal collapse, which is serious black-smoke time.

Almost anything that stops the flow of air is black smoke time, IME.

--
Paul ...
(8(|) Homer Rules ..... Doh !!!

 
....and Paul - xxx spake unto the tribes of Usenet, saying...


> Graham G came up with the following;:

> As Alex and Richard have said, a replacement 'other make' carb is a
> very worthwhile investment. My S3 never ran properly with a zenith,
> but did with a weber.

No, what I suggested was a genuine Zenith, manufactured on the original
tooling by Burlen, who have bought all the tooling and rights to the name
etc from ?Solex?. Mine runs well and is showing no signs of failure so far.
If you have a look at the Series 2 Club forum

http://www.nhua.co.uk/smf_1-0-5/index.php

you will see that it's about 80/20 against Webers, mainly for their
propensity to ice up and also starve of fuel on steep slopes.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)


 
On or around Fri, 16 Dec 2005 20:33:49 -0000, "Paul - xxx"
<[email protected]> enlightened us thusly:


>
>Almost anything that stops the flow of air is black smoke time, IME.

ah, been working on this on the minibus - removing the restrictive inlet to
the airbox created more inlet noise and noticeably more power. Next
investigation is into ram-air effect...

Been considering the speed of the air in the inlet tract:

Engine size: 2.5l 4-stroke.
Inlet tract internal diameter (say) 6cm

So, the engine swept volume per rev. will be half the capacity, i.e. 1.25l.

6cm pipe has a cross-sectional area of about 28 cm² so the afore mentioned
1.25l of air occupies about 45cm of the said pipe. Suppose now that the
engine is doing 2200, that gives you 2200*0.45 = 990m/min. make it a tad
over 2200, and you have 1km/min which is 60 km/h

Now, suppose I duct the inlet to the front of the vehicle and point it
forwards, and do 60km/h at 2200 rpm, the incident air on the end of the pipe
is at the same speed as the air flowing into the engine, and as such, must
increase the inlet pressure slightly as compared with running at 2200 rpm in
still air. If I now attach a funnel, of say 12cm down to 6cm diameter, to
the pipe, I've got a 4:1 decrease in CSA of the pipe. I'm not daft enough
to believe that this makes the pressure at the small end 4x that at the
large end, because there are doubtless lots of reasons why not. But it must
increase the pressure a bit.

At lesser road speeds, obviously, the ram effect is less - but at any speed
there will be *some* effect.

All this can be done by potching about with bits of otherwise worthless tqt,
and if it makes the motor go faster or better, well and good.


OK, someone tell me it's all bollox...:)
--
Austin Shackles. www.ddol-las.net my opinions are just that
"You praise the firm restraint with which they write -_
I'm with you there, of course: They use the snaffle and the bit
alright, but where's the bloody horse? - Roy Campbell (1902-1957)
 
Austin Shackles wrote:

> OK, someone tell me it's all bollox...:)

Your reasoning seems sound enough Austin - when I tried the same sort of
thing with my motorhome there was a marked improvement in performance,
although no real gain in economy as the extra oomph tends to be
translated in a higher speed. As you say, there's nothing to lose
playing with it.

Re-work the maths for the diameter of the exhaust, factor in the thermal
expansion of the gas and then fit a decent bore exhaust - you'll prolly
make a similar gain there too.


--
EMB
 
Austin Shackles came up with the following;:

> OK, someone tell me it's all bollox...:)

Ok, it's all bollox ... ;)

Acksherlly it's not. Look back to the ram-air Suzuki 2 strokes of
yesteryear ... or the way that almost any racing car has similar ducts to
channel a positive pressure of air into the inlet. We used to do it on our
racing sidecar 'cos they had no airboxes to speak of, so central heating
flexible duct was used. The wider the better, we found.

What does help _a lot_ if you do make some positive pressure at the inlet is
to also do something to the outlet ... ;)

--
Paul ...
(8(|) Homer Rules ..... Doh !!!

 
....and Paul - xxx spake unto the tribes of Usenet, saying...

> Look back to the ram-air Suzuki 2 strokes of
> yesteryear ...

I thought the Ram-Air System was to force-feed the cooling rather than the
inlet. Big, forward-facing ducts over the cylinder head. BICBW, usually
am.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)


 
Richard Brookman came up with the following;:
> ...and Paul - xxx spake unto the tribes of Usenet, saying...
>
>> Look back to the ram-air Suzuki 2 strokes of
>> yesteryear ...
>
> I thought the Ram-Air System was to force-feed the cooling rather than the
> inlet. Big, forward-facing ducts over the cylinder head. BICBW, usually
> am.

It was ... but some people, I believe Suzuki did on the racers, also used it
to channel 'extra air' into the airboxes, especially the production racers
.... ;)

--
Paul ...
(8(|) Homer Rules ..... Doh !!!
ebay 8023391484

 
On Saturday, in article
<[email protected]>
[email protected] "Austin Shackles" wrote:

> On or around Fri, 16 Dec 2005 20:33:49 -0000, "Paul - xxx"
> <[email protected]> enlightened us thusly:
>
>
> >
> >Almost anything that stops the flow of air is black smoke time, IME.
>
> ah, been working on this on the minibus - removing the restrictive inlet to
> the airbox created more inlet noise and noticeably more power. Next
> investigation is into ram-air effect...
>
> Been considering the speed of the air in the inlet tract:
>
> Engine size: 2.5l 4-stroke.
> Inlet tract internal diameter (say) 6cm
>
> So, the engine swept volume per rev. will be half the capacity, i.e. 1.25l.
>
> 6cm pipe has a cross-sectional area of about 28 cm² so the afore mentioned
> 1.25l of air occupies about 45cm of the said pipe. Suppose now that the
> engine is doing 2200, that gives you 2200*0.45 = 990m/min. make it a tad
> over 2200, and you have 1km/min which is 60 km/h
>
> Now, suppose I duct the inlet to the front of the vehicle and point it
> forwards, and do 60km/h at 2200 rpm, the incident air on the end of the pipe
> is at the same speed as the air flowing into the engine, and as such, must
> increase the inlet pressure slightly as compared with running at 2200 rpm in
> still air. If I now attach a funnel, of say 12cm down to 6cm diameter, to
> the pipe, I've got a 4:1 decrease in CSA of the pipe. I'm not daft enough
> to believe that this makes the pressure at the small end 4x that at the
> large end, because there are doubtless lots of reasons why not. But it must
> increase the pressure a bit.
>
> At lesser road speeds, obviously, the ram effect is less - but at any speed
> there will be *some* effect.
>
> All this can be done by potching about with bits of otherwise worthless tqt,
> and if it makes the motor go faster or better, well and good.
>
>
> OK, someone tell me it's all bollox...:)

The main thing you've missed is that the air temperature will rise,
tending to reduce density. So the mass flow will be reduced, and it's
the mass of air which matters to the combustion process.

That's why intercoolers make a difference to a turbocharged engine (or
supercharged). It's also why water/alcohol injection makes a difference.

But it's probably going to be masked by the detail effects of the intake
design.


--
David G. Bell -- SF Fan, Filker, and Punslinger.

"I am Number Two," said Penfold. "You are Number Six."
 
On or around Sat, 17 Dec 2005 10:45:11 -0000, "Paul - xxx"
<[email protected]> enlightened us thusly:

>Austin Shackles came up with the following;:
>
>> OK, someone tell me it's all bollox...:)
>
>Ok, it's all bollox ... ;)
>
>Acksherlly it's not. Look back to the ram-air Suzuki 2 strokes of
>yesteryear ... or the way that almost any racing car has similar ducts to
>channel a positive pressure of air into the inlet. We used to do it on our
>racing sidecar 'cos they had no airboxes to speak of, so central heating
>flexible duct was used. The wider the better, we found.
>
>What does help _a lot_ if you do make some positive pressure at the inlet is
>to also do something to the outlet ... ;)

yeah, thought about that. I rather think the exhaust may be the same for a
turbo engine, though - if it is, then it's got the additional capacity. but
it's easily checked.

hmmm. Bosal list 2 exhausts, one turbo, one non-turbo... But, the only
part that's differnt is the front pipe. The main box, intermediate pipe and
rear box/tailpipe are all the same part numbers. SDo I reckon the exhaust
shouldn't be too restrictive.
--
Austin Shackles. www.ddol-las.net my opinions are just that
"I am tired and sick of war. Its glory is all moonshine... War is hell"
Gen. Sherman (1820-1891) Attr. words in Address at Michigan Military
Academy, 19 June 1879.
 
Richard Brookman muttered summat about:

> ...and Paul - xxx spake unto the tribes of Usenet, saying...
>
>
>> Graham G came up with the following;:
>
>> As Alex and Richard have said, a replacement 'other make' carb is a
>> very worthwhile investment. My S3 never ran properly with a zenith,
>> but did with a weber.
>
> No, what I suggested was a genuine Zenith, manufactured on the
> original tooling by Burlen, who have bought all the tooling and
> rights to the name etc from ?Solex?. Mine runs well and is showing
> no signs of failure so far. If you have a look at the Series 2 Club
> forum
> http://www.nhua.co.uk/smf_1-0-5/index.php
>
> you will see that it's about 80/20 against Webers, mainly for their
> propensity to ice up and also starve of fuel on steep slopes.

Many thanks indeed to everyone that has offered input, have passed it all
on. Emphasis has shifted slightly today; he wasn't getting far with the carb
so he thought he would finish off the electrics. For some inexplicable (atm)
reason the side light that has worked up until thus point, caused a short.
this failed to blow the correct sized and installed (checked both) fuse and
promptly melted the brand new wiring lume that he fitted some months
previously. He was almost crying at this point. So he has had to pull the
lot out and set about bypassing the damaged wires.

Incidentally, we have been offered a workshop with enough room for 4 lifts,
heated, offices, changing room, kitchen, parts store and alarmed. Whats it
worth to rent? We have been struggling to decide what a sensible figure for
such a place would be.

--
Graham

101 GS
101 Rad Bod


 
Paul - xxx wrote:

> Richard Brookman came up with the following;:
>> ...and Paul - xxx spake unto the tribes of Usenet, saying...
>>
>>> Look back to the ram-air Suzuki 2 strokes of
>>> yesteryear ...
>>
>> I thought the Ram-Air System was to force-feed the cooling rather than
>> the
>> inlet. Big, forward-facing ducts over the cylinder head. BICBW, usually
>> am.
>
> It was ... but some people, I believe Suzuki did on the racers, also used
> it to channel 'extra air' into the airboxes, especially the production
> racers ... ;)
>

Most modern big sports 'bikes have some form of ram-air induction system.
There is a sort of test of how well it works by simulating it on a dyno
here:

http://sportrider.com/tech/146_9912_ram/

Not sure how accurate it is compared to on the road!
--
Ray
 
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