Su carbs not Carbing....

[111Robin]

If you hadn't said that it was running before with the single carb I would have immediately advised that you check the timing. It is still advisable to do so I would think as there's no point trying to tune carburettors if the timing is out. Are you running points or electronic set up ?.

[AndrewGilbert]

Morning, electronic and we have strong sparks.
I'm convinced its carb related as thats the only item I've made a change to. And I have a feeling its choke related. These pair have the operable choke on a single HS4 and not both, used successfully before on our previous 1293 but looking at the cable, its pulling through the hole so I'm not convinced thats working as it should as the knurled end that sits in the hole is missing. But I may have these off and install the linkage to run both.

[Peter Laidler]

If you were local (where are you..... It always helps to know), we'd have them off, reset mechanically, firing and adjusted as per a colourtune in 1 and 4 cylinders plus toast and a cup of tea, within a couple of hours

[Polarsilver]

OK you have Fuel ..but how old is it ?.. suggest you drain tank & carbs & refilll with fresh..

[timmy201]

You can try dropping the jet on the unchoked carb and holding it down with a peg or cable tie just to rule that out

Or spray some brake cleaner down the carb throats

I’ve also successfully used a set of twins with a single choke and they started up fine

[111Robin]

Morning, electronic and we have strong sparks.
I'm convinced its carb related as thats the only item I've made a change to. And I have a feeling its choke related. These pair have the operable choke on a single HS4 and not both, used successfully before on our previous 1293 but looking at the cable, its pulling through the hole so I'm not convinced thats working as it should as the knurled end that sits in the hole is missing. But I may have these off and install the linkage to run both.

I would agree,, if it ran previously then the timing wouldn't be an issue. As mentioned above, pull both jets down manually and lock in place with something if the cable isn't operating. It sounds like it is trying to fire but the mixture isn't rich enough for a cold start. You've done the right thing stripping and resetting the jets etc. so now it can only be the inoperative choke(s). I wouldn't worry about the fuel, mine sit for at least five months without running and I never have any issues with it. Fuel can be variable depending on the time of year and quality (ie. supermarket shite or decent stuff) and how the car is garaged so some folk have issues, others don't but unless you're really unlucky it will likely be ok, just top it up with some fresh stuff to help it.

['S'-type]

I'm not sure if it has been mentioned yet, but the float valve setting needs careful consideration. If the fuel bowl level is too low it can be enough to cause a non-start.
With the suction chambers and pistons off you should see fuel about 3/8" down from the bridge of the jet. Can't remember the figure for setting the float level lever gap off hand.
If you haven't already tried chucking a thimble of fuel in to the inlet that would instantly tell you fuel delivery is the problem if it fires. If it doesn't try to fire it's not a fuel issue.

Fuel height2.JPG

[MiNiKiN]

I'm not sure if it has been mentioned yet, but the float valve setting needs careful consideration. If the fuel bowl level is too low it can be enough to cause a non-start.
With the suction chambers and pistons off you should see fuel about 3/8" down from the bridge of the jet. Can't remember the figure for setting the float level lever gap off hand.
If you haven't already tried chucking a thimble of fuel in to the inlet that would instantly tell you fuel delivery is the problem if it fires. If it doesn't try to fire it's not a fuel issue.

Fuel height2.JPG

Here are the various float height settings...
https://sucarb.co.uk/technical/technica ... oat-height

[AndrewGilbert]

Thank you Minikin and S type.

I've narrowed it down to the floats I hope. I have fuel under the inlet manifold which to me means its not producing the fine mist it should and is dumping fuel out into the manifold. But I have HS4's which might be non adjustable, however I need to look at the floats tomorrow to see exactly what I have.

A few steps at a time.

[Spider]

Are the Spark Plugs wet or dry ?

[AndrewGilbert]

Are the Spark Plugs wet or dry ?

They're getting wet so fuel is getting in. However there is no fuel regulator to ensure I have the correct pressure so have sorted that now and I've yet to look at the floats, so that for this pm.

[gazza82]

Check the fuel is getting through the small pipes from float chamber to jets. The pipes get twisted and with ethanol they could be blocked if this is attacking the rubber.

[AndrewGilbert]

A further update, we checked the floats, have later non adjustable type but those were within the dims noted online. Spark plug gaps were all good. Fitted a fuel pressure regulator with filter so now have clean fuel going in) and then after a fashion managed to get it to run although it ran badly, back fired, popping etc, badly adjusted, started on easi start and sort of idled but after about 30/45 seconds started to die and as soon as I touched the throttle it died. It won't fire as when it does and you release the key it doesn't catch.

But the back firing and popping when it did run or when it tries to fire leads me to a possible air leak as mentioned before, and then we spotted the inlet manifold has a small hole in it that we'd covered with a tape at the time when it was stored (black inlet, black tape, hidden by pipework!) and I think that was a take off for a feed into the inlet for vacuum originally, so we'll repair that and get the carbs back to their correct settings and go again.

[AndrewGilbert]

If you were local (where are you..... It always helps to know), we'd have them off, reset mechanically, firing and adjusted as per a colourtune in 1 and 4 cylinders plus toast and a cup of tea, within a couple of hours

I'm in Cambridge, but its going to get to the point where I'll need to get someone in to get this running if we can't over the coming weeks. In the meantime I have a lot to do with suspension adjustments, interior stuff and basic exterior updates whilst the non start persist.

[Peter Laidler]

Anyone near to Cambridge that can help Andy with his carb problems. I'm sure that someone fairly local will pipe-up.

[Allen Brzeczek]

It is a shame, my wife had a hospital appointment in Cambridge week-end ago, we stayed over for a couple of nights and I had plenty of time on my hands while she was in treatment and would have gladly made an offer of help. not sure at this time when or if we will need to return in the near future. However, in my case as having managed to assemble a mismatch set of HS4 carbs which then fired up relatively easily I am puzzled especially as there has been plentiful pertinent advise via forum members.

It appears that this has been helpful but I understand the situation correctly the float chambers are filled with fuel but it does not appear to be drawn into the engine. Presumably there is a healthy spark therefore I would consider the question of induction air leaks also the quality of the fuel. If we have no leaks and the fuel is fresh I would have thought by setting the carbs initially on the rich side or the use of quick start you should have seen some life by now.

A couple of things spring to mind firstly, in my case I used new jet tubes and connecting pipes to the float chambers, are these blocked ? I had an episode this weekend with a garden mower which would not run, I discovered that last years fuel in the bowl had evaporated leaving a crystalline substance which blocked both the petrol inlet and main jets - possibly a characteristic of our modern fuels. But assuming everything has been checked and all is good the last thought I have, possibly a will be seen as silly one, the question I would ask is has the distributor been disturbed and now out of sync

[111Robin]

You stated previously that the choke wasn't operable by the cable, have you sorted this or did you manually pull the jets down for the cold start ?.
I also second the previous query on the distributor, do you know what the advance is set at ?. Spitting back could also be a sign of incorrect timing. Set it to 5 deg BTDC static and it will start if there are no fueling issues.

[AndrewGilbert]

Cheers both. It ran although for a short while so I'm hoping its an air leak thats causing the main issue. I'll have another go this weekend. Choke cable still needs resolving but I held the chokes open manually.

The car was running before I swapped the carbs out so I don't believe its the timing. Its bound to be something simple I just can't see it! But if I do have a small hole in the inlet that on its own will cause a number of problems, pity I found that whilst packing up!

[DougR]

Hi, has the "pump going like the clappers" problem been resolved? If there were a blockage or if the floats were doing their job the pump should stop. You also state that you don't smell fuel and therefore there's no leak. So my thinking is that the fuel is being pumped straight into the manifold/ engine via the jets which might also explain the starting problem. It's flooded. So the next question is, assuming as discussed you've adjusted the float needle gaps, are the float chambers perfectly vertical? I had a pair of HS4s that came off a Marina and the float chamber angle was wrong for a mini. Just a thought. Cheers, Doug.

[minime]

Hi, just a thought but what angle are the float bowls ? Are they the same as the carb you had on?