Herald 1200 jerking/surging/kangarooing

[Morgana]

I'm not sure what to call this. In the last journey the Herald was not maintaining a constant speed well. Constant pressure on the accelerator led to a strong feeling of surging back and forth as if drive power was cutting in and out, so speed was increasing and decreasing. Not as bad as driving-school kangaroo, but a similar sensation. Acceleration appears fine. Idling is quiet and even. Last week some 6k mile service items were completed including oil change, valve clearances, dressing points and sparking plug gaps. Plugs were in good condition. The week before, changing the offside universal joint cured the ticking noise on that side.

I wonder if this problem could be:

• the clutch slipping (there is judder starting in 1st, but not having any experience of other Triumphs I don't know if this is a normal amount or not). The clutch otherwise engages and disengages without excessive pedal travel.
• Gearbox. The previous owner said the gearbox had not been overhauled. 3rd is noisy and the gearstick shakes. I guess an overhaul kit is needed as I think the synchromesh wheels are worn. However, acceleration and engine braking is OK without judder or speed variation.
• Fuel. Another family member remembers driving the car earlier in my ownership and experiencing a similar bucking using lead substitute that came with the car. Since then so much tuning has been done it's hard to tell if the fuel or additive isolated from other work could be to blame. Certainly the easiest to test on next fill up, but in the interim I wondered if any other owners had similar experiences.

 

[NonMember]

That sort of surging or bucking is very unlikely to be a clutch or gearbox issue. It could well be a fuel problem, though, or an ignition problem. If it were running SU or Stromberg carbs I'd say make sure the dashpot has some engine oil in it. I'm not sure what the equivalent "common issue" on a Solex would be.

[Pete Lewis]

i agree discount the drive line  you say it idles aok but do check 

the slow running jet is external and unscrews with screwdriver  check its not got a small deris in it.

have you messed with the fuel system  , changing fuel hose can make small rubber slivers that part block the float needle valve

check the short rubber hose on top of the fuel tank is tight , these deteriorate and the pump sucks air more than fuel 

check the fuel pump for crap in the chamber , 

any back fires??      the condensers on sale some are terrible   always get them from the distributor doctor

 Delco condenser: 829111,829107,1861709,1866049,18655972, 1869704,1882239, Lucas Condenser 484249, 400308, 407044, 54411935 / DCB105, 54413006, 23D4 22D 23D DM2 25D DM6 DM4 lucas distributor, Lucas condenser number 423871, GDC101. Condensor 405833 for Ford 8 and Ford 10, Lucas condensers from Distributor Doctor

as you have checked the points i would revisit make sure the gap is correct and things are secure, check the braided covered earth wire is intact

check the HT brush in the top of the dizzy cap is intact and does contact the rotor arm

dont use a rotor arm witha rivet in the sweep plate these fail and the HT is run to earth via the rivet

thats a lot to think about  let us know what you find if any 

Pete

 

[Badwolf]

I agree with Peter and N/M. I had very similar experiences. Sorted by adjusting SU2 carbs and choke !inkage which was causing plugs to soot up.

[daverclasper]

On 02/10/2022 at 16:48, Pete Lewis said:

dont use a rotor arm witha rivet in the sweep plate these fail and the HT is run to earth via the rivet

I understand, a dodge (maybe just to eliminate?), is to put a finger, off a surgical glove over the rotor shaft/Cam?

[Pete Lewis]

Dave   i think the HT would just jump that  

but if you get a failure let us know if it helps  

Pete

[NonMember]

22 minutes ago, Pete Lewis said:

 i think the HT would just jump that

I suspect the insulation strength of surgical glove material is rather higher than that of air, so it may work.

[daverclasper]

I remember someone mentioned an AA guy, had got someone going by doing this?

[Morgana]

A follow up to this - I'm sorry to leave you hanging on!

The short length of hose between the fuel line under the car and the pump entry was disintegrating. Bizarrely it was fine a couple of weeks previously when last checked and poked, but this time was delaminating and had incipient fissures. It's been replaced with proper hose and the problem disappeared. Since then I've put on a new Distributor Doctor distributor and leads, which means I can see the markings on the vacuum advance which were missing on the old distributor. A new job forty minutes' drive away means it needs to be reliable at least until the trains settle down. 2,000 miles since the end of September with no other major issues.

I went over all the fuel lines to replace the connecting hoses and couldn't find the rubber connector that's marked as being somewhere under the car. Is this present on all examples, or could a previous owner have replaced it with a single length of rigid piping? If it's present, where exactly should I be looking for it?

I've added another washer to the float valve which testing on the drive suggests has stopped the switch-off leak. Now to keep track of fuel consumption...

[Colin Lindsay]

There may be no rubber pipe connector if a PO has replaced the fuel lines with one 'straight-through' pipe from tank to pump. I just use a single length on all of mine, less to go wrong.

[Morgana]

It does seem more sensible! Let's hope that's the case. I was looking again today as there was some persistent (though less pronounced) surging etc. I discovered the carburettor was a little loose on the manifold, so I hope that was causing enough of an air leak to create similar symptoms at light load. Tomorrow will tell... 😉

[Pete Lewis]

and while you are twiddling remove the slow running jet on the side of the solex make sure its clear 

its the small  brass jet with a hex head and scredriver slot   give it a blow through  

if its blocked clearing may need the idle mixture svrew adjusting to best running and even a reset od the idle  speed 

Pete