low in power, lean mixture? 1850HL

[Carledo]

Let's assume for a moment that your ignition system is good enough for now and that dwell angle and timing are OK, or, at least, within the realms of reason.

The car ran OK - ish! But you had reason to suspect the rubber carb mounts were faulty. Not unreasonable.

You have replaced the carb mounts and also the jets and needles with suitable bits and slightly richer needles. I have to take the needles on trust as I can't carry all the data and characteristics of al the many needles in my head. But ABT needles ring a bell as being suitable.

You have balanced the throttles and set the mixtures equally at 12 flats (2 full turns) below the "bridge" which is the base setting for SUs and have no obvious air leaks. You have also confirmed full throttle operation as being available. You have sufficient fuel pressure.

As far as I can see you have done everything right and it should work! In fact I often find that with older carbs, even with new needles and jets, the best running mixture is nearer 9 flats than 12, so somewhat leaner.

Yet the car is lacking any sensible power in the higher rev ranges and under larger loads and the idle is rougher than you would expect. Even running with the choke out, or richening to (so you have said) a massive 30 flats (5 full turns) hasn't helped!

And the general running is WORSE than before you started.

Am I getting things right so far?

From this information, either (in no particular order) a) you made a mistake somewhere, b) you are a victim of substandard or faulty or incorrectly supplied parts or c) there is another underlying problem that has been highlighted by bringing the fuel system up to scratch.

Let's forget the mistake for now, if you made one, it will be for you to find it. Let's also eliminate possibly faulty waxstats, again, I can't judge their function from this distance. But getting 2 matching duff ones does seem unlikely.

Available data indicates that either a) there is a MASSIVE undiscovered air leak (which you are sure is not the case) b) the advance curve is so totally wrong that it may as well not be there or c) there is a deeper problem possibly involving camshaft timing.

At this point, I think i'd be looking long and hard at the distributor, I suspect something within it may be seized up solid! And follow it up with checking the cam timing.

Steve

[DOLOMITE 135]

Apart from the work already noted, A few queries come to mind:
Was any other work done to the Carbs or parts replaced that's not already been mentioned?
Did you internally clean them if so how?
Were the carbs worked on individually or at the same time, could parts have been mixed between them?
Have you done a piston drop test?
Were parts from other carbs used (for instance the su carb piston damper for a single carb setup is different from a twin carb and using the wrong one would be detrimental).
Before adjusting the jets did you check with the top of the carbs off that both the jets were at the same height?
When you said both the throttle opens fully are you using the pedal the to check this or the linkages?
Do both the butterflies move in unison with the linkages?
Does the choke operate equally on both carbs and shut off fully?
How did you balance the carbs?
Have you checked the air filters are not upside down?

In order not to assume the problems are to do with the work just completed, as you do not indicate the time-scale this work was completed in, it might be worth checking other items such as:
Distributor advance / retard not stuck (plus vacuum line from carb intact
You do not state what type of fuel pump you have, but the newer type currently available with the top of the body screwed to the bottom can have the screws come loose which results in a loss of suction and reduced fuel delivery (this happened to my 1850). As an aside I fitted a brand new pump to my Toledo recently and promptly broke down 100m down the road when the float chamber needle / seat became blocked from a loose piece of the adhesive used to bond the hose connectors to the body, have you checked both float chambers are getting fuel equally.

[Bumpa]

I like the suggestion that the air filter gaskets could be upside down. That would block off two important holes.

[GinettaG15]

I like the suggestion that the air filter gaskets could be upside down. That would block off two important holes.

interestiing note, but during adjustment of the carbs the filter was off....so cannot be the cause.

this said, in the later test drive the filter was back on...but the gaskets are correctly mounted.

[GinettaG15]

Apart from the work already noted, A few queries come to mind:
Was any other work done to the Carbs or parts replaced that's not already been mentioned?
Did you internally clean them if so how?
Were the carbs worked on individually or at the same time, could parts have been mixed between them?
Have you done a piston drop test?
Were parts from other carbs used (for instance the su carb piston damper for a single carb setup is different from a twin carb and using the wrong one would be detrimental).
Before adjusting the jets did you check with the top of the carbs off that both the jets were at the same height?
When you said both the throttle opens fully are you using the pedal the to check this or the linkages?
Do both the butterflies move in unison with the linkages?
Does the choke operate equally on both carbs and shut off fully?
How did you balance the carbs?
Have you checked the air filters are not upside down?

In order not to assume the problems are to do with the work just completed, as you do not indicate the time-scale this work was completed in, it might be worth checking other items such as:
Distributor advance / retard not stuck (plus vacuum line from carb intact
You do not state what type of fuel pump you have, but the newer type currently available with the top of the body screwed to the bottom can have the screws come loose which results in a loss of suction and reduced fuel delivery (this happened to my 1850). As an aside I fitted a brand new pump to my Toledo recently and promptly broke down 100m down the road when the float chamber needle / seat became blocked from a loose piece of the adhesive used to bond the hose connectors to the body, have you checked both float chambers are getting fuel equally.

when the car came to me it was starting well, reacted well on accelerator, but idle was totally lumpy.

investigations turned out that the front carb rubber mount was cracked and having an air-leak

so i replaced the mounts by alloy ones.

refitted carbs, adjusted them, but idle was still a bit lumpy and to achieve a reasonable result i had to lower the front-carb´s jet massively compared to the rear. and thats how the car came to me already.

so i investigated: both needles were the original ABK´s , but the front Needle was "grinded" slimmer(richer)...i guess to compensate the air-leak of the cracked rubber-mount.

i also recognized that on the rear carb the hose-connection from the jet to the float chamber was leaking on the chamber side.

so i ordered a set of new waxstats and a pair of ABT needles:

those needles are slightly richer in the mid range....but really not much...and on low and top-end they are more or less equal to the ABK´s

https://www.classicminidiy.com/technical/needles/

this has been done because most experts say that the original fitment (ABK) is a bit on the lean side.

after fitting the new waxstats and the needles i could adjust the jets on both carbs on a similar / equal level.
engine started reasonably well, but needed a longer choke phase than before.

other things than above described have not been done to the carbs. float chambers are clean, throttle spindles not worn out, throttle fully opens when pushing the accelerator-pedal.
i have not used any parts from other carbs
i have done carb by carb to avoid mixing parts.
the needles have been fitted to the pistons on an equal-level.
choke mechanism isnt sticky and the levers move back in zero-position.
carbs are balanced with such a device, as i´m more working with Weber´s in the past:
https://classiccarbs.co.uk/product/webe ... nchronizer
but i have used those balancers on other SU-powered carbs already and could always achieve a good result.

my (mechanical) fuel-pump is old ...but delivers more than enough fuel...i also fitted , as test, a low-pressure electic pump, which had no effect on the running.

dizzy is old, but working ok....i have just received a refurbished-one. this one will be converted to point-less (electronic) and fitted once the engine is runnign again well.

i dont want to touch too many areas at once....the igntion worked well before, the car run so-ish ok before...so someting has gone wrong when changing to alloy-mounts and new waxstats....

[DOLOMITE 135]

If the car has been run for some time with one of the carbs running much richer than the other, I would want to do a compression test on the engine to ensure the richer cylinders have not suffered from cylinder wash.

You say the top speed is now about 55mph, is this better or worse than before?

I note you intend to replace the distributor, if the engine is worn enough to consider a new distributor I would also check the timing gear by putting the crank on TDC, taking off the oil cap and checking the cam marking against the cam cap, on mine the cam was off about 6 degrees when the crank was on zero due to wear in the timing chain and sprockets. Changing the timing chain and sprockets made a big difference.

[GinettaG15]

i havent driven the car properly when i bought it...just out of the garage from the former owner, up and down the road (gently) , onto the trailer and thats it. but i could already feel that the car had proper power.

than i started the repairs...after the repairs i drove it the fist time "properly"

the replacement dizzy has nothing to do with a worn dizzy...its a different matter.

the car has original 50k miles....

[xvivalve]

What’s the condition of the points?

[Bumpa]

"so i ordered a set of new waxstats and a pair of ABT needles:
those needles are slightly richer in the mid range....but really not much...and on low and top-end they are more or less equal to the ABK´s"

On the recommendation of the late Jon Tilson, whose experience of the 1850 was vast, I fitted richer needles type AAA. Jon always said that the needles specified for the 1850 with SUs were too lean. My car performs well with these AAA needles and is certainly not over-rich. Plugs are a good colour and fuel consumption is very acceptable.

[GinettaG15]

What’s the condition of the points?

honestly: poor in power, where pulling-choke is needed to accelerate, has nothing to do with points....but just to give you a reply:
the engine behaves in the same way with good-quality used points as well as new points. same applies for new vs old cap and finger.

its something mixture-related...definately.....

today started snowing and its ice-cold in my garage....so no motivation to do some work.....

[soe8m]

One of my hobbies is to have Dolomites running again from a distance by checking step by step by messenger or whatsapp. Easy communication and easy to send pics to see what you did.

But you do need to leave the '30 years experience mindset' behind otherwise it won't work. I have no time for discussing or argueing.

Jeroen

[xvivalve]

At the outset you stated:

anyway, gave it a test drive....and no ... bout 55mph

Unless something was lost in translation, that to me is a prime potential symptom of knackered points, but if you've already looked at that, so be it.

Take up Jeroen's offer.

[cliftyhanger]

I recently built a fresh engine for a mk3 spit. I bought a used delco distributor and used HS2 carbs for it.
Set everything up as per "the book" and indeed, started after cranking with plugs out to get oil pressure up.
But it wasn't happy. As we know, the vast majority of fuelling issues are down to the ignition system.
I found the "old" points and condensor, which appeared not very old. Cleaned the faces on te points, and tried those. No different.
Like you, I had a EI module waiting to go in. I relented, and tried the EI. Instant change to the running before I retimed the ignition. Smooth, clean idle. It all felt much better.
It seems madness that you won't eliminate the points and ty the EI.
Have you also checked how much mechanical advance you are getting? I have had 2 distributors which were worn so badly they gave only a few degrees.

You can check your waxstats using a heat gun, see how much it weakens the mixture.

If there 2 things I have learnt from my mere 30 years of playing with Triumphs, it is (1) new parts are often crap and simply do not do their job properly (2) waxstats are te spawn of satan.

But as above, you have had an offer that will resolve your issues from Jeroen. T+Cs are clear and well justified.

[GinettaG15]

One of my hobbies is to have Dolomites running again from a distance by checking step by step by messenger or whatsapp. Easy communication and easy to send pics to see what you did.

But you do need to leave the '30 years experience mindset' behind otherwise it won't work. I have no time for discussing or argueing.

Jeroen

Jeroen, i appriciate your offer to help me and i´m more than willing to to leave my 30y mindset behind.

but i dont want to waste your time too much, so let me first check some basics again...and if i wont be able to solve it myselves, i would come back to you, if you agree?

this said: it might take some time, as its so cold in my garage that my motivation is like the tempertures : Zero.

[GinettaG15]

Update:
i converted the dizzy to electronic (accuspark), set the timing to 11degrees BTDC, new plugs (coil and HT leads were already changed before). centrifugal advance tested: ok, vacuum advance tested: ok
wax inside the copper-capsule, on the new waxstat-jets, has been removed.

carbs haven been set with jets 2,5turns below the brigdge, throttle stop screws 1 turn down after in contact with the lever.

engine started on the button (with choke fully pulled)....after a short warm-up period the choke could be pushed back, the enigne was falling in a smooth and constant idle of around 900rpm.