Mystery Carb Modification?

[utilly]

I picked Gladys up from the body shop and ran her back home last night. I noticed that she seemed a bit underpowered, but it wasn't a problem seeing as I came back via the backroads.

Anyway, I was out today walking the dog when I bumpped into Rob, our local handyman/boat engine repairer. I asked him if he knew anything about Minors and it just so happened that him and his father used to show A40s (?) and Minors donkey years ago. I described the symptoms and he said that it was my carb. He whipped the bonnet up and checked the oil level (woefully low) and gave me a carb 101 lecture which leaves me much the wiser.

However he did say that there was something unusual about my carb and suggested that I took a photo of it and asked if anyone could shed some light on it for me. I have taken the photos from the drivers side, to give the clearest view.

The top picture is of the mystery modification. Essentally, t's a little bit of rubber tube, loosely jubilee clipped at the bottom with a bolt in the top. The thing isn't on very tightly and can be pulled off to reveal the tube that it covers in the bottom picture. Can anyone tell me what should be in it's place or what it is there for?

http://bitter.custard.org/mysterycarbmod/

Also it looks like there is a little bit of a fuel leak on the flexible hose from the one bit of the carb to the other (see how well I retained all that info from my carb 101?).

He has said that it is not a big job to sort out the carb and tube and that he would show me how to do that and change oil and filters and lubricate etc when we get the boy back from the States (double the chance of retaining the info!) for just the cost of his time and that I could probably do some trade for my time, fixing his computer and switching him over to Linux... once he replaces the disks that he smashed in January.

So, can anyone tell me what my mystery mod is for or should do and what I can replace it with? I can't find anything that looks like *that* in all of my many manuals.

thanks

Tilly

[mu0u207b]

Looking at your photos its looks that the pipe on the side of your carb is the engine breather pipe connection at the carburettor end. This is standard on SU carbs. There should be a pipe running from that connection to either a pipe on the cylinder side cover or from a pipe on top of the rocker cover at the top of the engine. If that is missing that may explain why your car is lacking a bit of power.

[les]

There is also a small plastic tube, with a flange one end, that drops in this brass outlet that is on your carb, it is basically a restrictor, that reduces the diameter. The flange just stops it being pushed in too far. The hose is then fitted over the outlet and the other end connected to the cam follower cover (fitted with a cylindrical canister) I've have been unable to discover if this reducer is needed in all cases, anyone here with the answer?
If you're not using closed circuit breathing, blank it off, otherwise you will run weak.

[utilly]

There should be a pipe running from that connection to either a pipe on the cylinder side cover or from a pipe on top of the rocker cover at the top of the engine. If that is missing that may explain why your car is lacking a bit of power.

Thanks, I know what the rocker cover looks like, but I can't find anything that looks like it should have a tube on it. I am not quite sure where/what the cylinder side cover is located/looks like. Perhaps someone would like to describe it or better yet send me a pic?

Also, it looks like the fuel leak is worse than I thought... it appears to be comming from the float chamber end, but I can't keep her idling on her own long enough to nip arround and check under the bonnet without her stalling.

regards

Tilly

[TerryG]

when i need to wedge the throttle open a bit on mine i wedge a spanner into the throttle on the carb to hold it open slightly. Usually stops it stalling straight away (remmember to take it out afterwards though )

[Stig]

Thanks, I know what the rocker cover looks like, but I can't find anything that looks like it should have a tube on it. I am not quite sure where/what the cylinder side cover is located/looks like. Perhaps someone would like to describe it or better yet send me a pic?

Can't do a pic, but the "cylinder side covers" (or tappet chest covers) are a pair of rectangular covers on the side of the engine block underneath the manifolds. They each have a single bolt on the middle holding them on. On some Minors (the later ones I think) the front cover has a curved pipe coming out of it which is the breather pipe. This has a rubber hose going into the carb where yours is cut short and plugged with the bolt & jubilee clip. What it's for is to suck the oily fumes out of the bottom of the engine (crankcase) and burn them with the petrol to reduce pollution.
Maybe someone else (Cam?) knows what arrangement (rocker cover, side cover etc.) you car should have for it's year.

A thought: does the power pick up with higher revs but is really bad near idle? If so it sounds like an air leak, so if the "mystery" pipe isn't blocked off properly that might cause the problem.

[Cam]

I'm not sure when the different breather systems changed over as I don't have any reference material with me at the moment, but to be honest for breather info on the 1098, Willie's your man!

[bmcecosse]

Don't take chances with bits wedged in the throttle mechanism ! Just turn the idle screw up as far as necessary.

[utilly]

If so it sounds like an air leak, so if the "mystery" pipe isn't blocked off properly that might cause the problem.

I think that this does sound like it might well be the case. The mystey mod, I'm guessing, is not airtight because I can pull it off quite easily with my fingers. I notice since I have been running the engine and checking revs, that the exaust is a bit black and sputtery on the garage floor.

I had a good look at those two covers under the manifold and couldn't see any hole for a pipe, blocked or open. I went back to the 'Gladys' large history file. The owner before dad had a reconditioned engine put in there in the 80s. I am guessing that it was an earlier 1089 engine with no engine breather hole, but I think the 1970 carb is the original one, with the breather. Do I need to block the carb breather thingy off, and what would be the best way?

Also Dad had a new petrol pump put in recently. He thinks that some petrol crud may have made it's way into the float chamber which is causing it to overflow. It really is throwing out more petrol than I am comfortable with.

I have noticed that on one of the minor parts websites, they do kits to refurbish carbs, kits to rebuild carbs and refurbished carbs. I have no clue which one I want. I am happy to have a go at cleaning and rebuilding the carb (if the general consensus is that it's pretty easy, and pretty quick to do), once it is out, but I'm not sure how to get it out without getting petrol all over the place. If I don't do it myself and take her over to my trusty local garage, how long would a rebuild take and would it be cheaper to get a reconditioned unit?

Thoughts would be most welcome... I hate that my shiney new toy is still sat in the garage and not being driven!

Tilly

[bmcecosse]

If the carb is overflowing then the needle valve must be sticking - or the float inside is punctured. Don't start overhauling the carb when you don't know what you are doing ! Just take the top off the float bowl and clean it out - also switch on the ignition for a few seconds to flush out the needle valve - then hold it shut and get someone else to switch on - no fuel should come through. If it does - fit new needle valve.
All Minors have a breather on the side cover unless you have a 1275 fitted ? Just block the hole in the carb - the pipe with bolt is perfectly good enough - but better really to connect it to the breather tube on the top of the rocker cover. This will swallow the engine fumes making life inside much nicer - and fewer leaks from the engine too !

[Stig]

Ahhh, probably running rich then if it's spewing petrol about. I thought it might have been lean due to an air leak. I wouldn't worry too much about the breather just yet as it seems there's nowhere to connect it to on your recon engine -you can sort that out later. Petrol leaking from the carb would be the priority!

[utilly]

If the carb is overflowing then the needle valve must be sticking

Crud in the needle valve was indeed the culprit. I have also tightened up the tube on the carb and she seems to be running sweet now. Thanks, for all you contributions.

[Willie]

I have come in a bit late on this one and am not at all sure what
model year you have? As you have been told the carb is of the
last type fitted to Minors with 'closed circuit' breathing. with this
type you would have had a pipe from a side tappet cover going
to the mystery fitting on your carb and the OIL FILLER CAP would
have a wire mesh in it to let air in. There was another type where
the rubber pipe went to a mushroom shaped fitment on the inlet
manifold and then on to the carb. If your carb pipe is blocked
off then the question is how is your engine breathing? Do you
by any chance have a cylindrical fitting protruding from the timing
chain cover? (this would be a 1275cc engine type). At this stage
it suggests that either someone has replaced your 'breather'
tappet chest cover with a solid one, or that you have the wrong
rocker box cover (no outlet pipe). I will correct that, if you have
a 1098cc engine then it is certain that you have an incorrect tappet
chest cover fitted. Your full engine number would be usefull.

[utilly]

Wille said:

I have come in a bit late on this one and am not at all sure what
model year you have?

She is a 1970 4 door.

OIL FILLER CAP would have a wire mesh in it to let air in.

Nope, no wire mesh.

There was another type where the rubber pipe went to a mushroom shaped fitment on the inlet manifold and then on to the carb.

Nothing even vaugely mushroom shaped in there.

If your carb pipe is blocked
off then the question is how is your engine breathing? Do you
by any chance have a cylindrical fitting protruding from the timing
chain cover? (this would be a 1275cc engine type).

Not sure what I am looking for here. Might be best that you look at a picture (thousand words and all that).

http://bitter.custard.org/mysterycarbmod/engine1.jpg

Your full engine number would be usefull.

10V/189E/H 7200 if that is any help.

thanks

Tilly

[Willie]

TILLY....Your 10V engine prefix is correct for the late 'controlled
breathing' type of Minor engine. You should have a cylindrical
breather outlet attached to your front tappet chest cover. A rubber
pipe should go from this to your mystery fitting on the carb. You
MUST couple this with fitting an OIL FILLER CAP which has an inbuilt
wire mesh filter (to let air IN). This arrangement would return your
engine breathing to how it left the factory. Having looked at your
pic it is obvious that you DO have the late type cylindrical breather
outlet but that you have it connected to the AIR FILTER via
that green pipe. this is wrong, that green pipe should go to the
mystery stub on your CARB. THERE SHOULD BE NO PIPE ON THE
AIR FILTER. If you have a solid(filterless) oil
filler cap at the moment then your engine has no way of taking in
air so is not running under correct conditions.

[bigginger]

Thanks from me for that, Willie - a little mystery explained for me, too. My 'geen pipe' is at present folded and cable tied out of the way, doing nothing (except, pesumably, pumping out fumes).

[utilly]

Willie (my font of engine knowledge) wrote:

TILLY....Your 10V engine prefix is correct for the late 'controlled
breathing' type of Minor engine.

Okaaayyyy.....

You should have a cylindrical
breather outlet attached to your front tappet chest cover.

That would be the cylindrical thing that sits at the front which has the green tube attached?

A rubber
pipe should go from this to your mystery fitting on the carb.

Which it is clearly not doing at present.... so this would be the first item on the shopping list?

You
MUST couple this with fitting an OIL FILLER CAP which has an inbuilt
wire mesh filter (to let air IN).

Would a oil filler cap with wire mesh filter be second item on the shopping list?

This arrangement would return your
engine breathing to how it left the factory.

Right, with you so far....

Having looked at your
pic it is obvious that you DO have the late type cylindrical breather
outlet but that you have it connected to the AIR FILTER via
that green pipe.this is wrong,

I did think it a little strange that I had a length of garden hose in there... it didn't strike me as an 'original' feature.

that green pipe should go to the
mystery stub on your CARB.

Which takes us back to item one on the shopping list...

THERE SHOULD BE NO PIPE ON THE
AIR FILTER.

Ok, this is where the next question comes in. If I have a chunk of garden hose attached to the air filter, which shouldn't be there, then what should attach to the hole in the air filter cap??? Is there a Third item that I should be adding to my shopping list or should I create my own 'mystery oil filter cap mod' out of bubblegum or a cork?!

If you have a solid(filterless) oil
filler cap at the moment then your engine has no way of taking in
air so is not running under correct conditions.

So, what on earth is the garden hose doing to my engine at the moment?

regards

Tilly

[bigginger]

I *think* it's filling the air filter with oil fumes/oil. Incidentally, by coincidence I took the 'cylindrical object' off yesterday, to find that the tube that leads to it was almost entirely blocked with 'mayonaisse', which I'm sure won't do the engine any good even if it is attached correctly. It's dead easy to scoop out with your finger, but wear plastic gloves!

[Multiphonikks]

Tilly,

I've not seen the whole of this thread until today - but I replaced Hebe's Breather pipe with a section of hose which I brought from a local autofactor. It cost me about £1 I think (if I remember correctly). Heater pipe should be okay (or some other rubber pipe which is okay with heat). I cut mine a bit on the long side so that in the summer I could move my air filter intake around so I could adjust how hot the air was going into the air filter

Nikki

[bigginger]

It doesn't go to the air filter intake on this type, Nikki - cylindrical crankcase breather to carb