either advance mechanism or carbs out of mix and balance, recheck with timing light and check the advance is working ( observe point travel while blipping throttle - should be about 8 degree advance capable, disconnect vac tube check again to show mechanical advance is also working ( flyweights and springs ) check in dizzy that the rotor spindle can freely turn on shaft, and while there turn the cap over, check for tracking and that there is indeed still a carbon in the center feed
skin1235,
Mar 24, 5:07pm
late thought, did you recently change the points And did you clean the new ones before fitting, and grease the cam And have you checked recently ( or then) for shaft wear or wobble in the dizzy, is the button located fully, does it fit the locator properly, is it new, is it the right button
another late thought, wait until really dark, leave the shed lights off, start it up and have a good look around under the bonnet, you'd be surprised how many things you'll see, sparks leaking out here and there, lights from inside the dizzy, even lights inside the plug ports on the dizzy cap ( bad),, intersting sight, and you'll probably have a idea which bits are meant to be there and which bits ( of light) aren't
mercbens,
Mar 24, 5:16pm
The Triumph 2500TC had twin Stromberg 150 CD carburettors as standard (not SU's). They have a rubber diaphragm rather than a piston to control the fuel mixture. If the diaphragms are not seating correctly or have a tear in one then it will not idle.
ginga4lyfe,
Mar 24, 5:20pm
http://www.flickr.com/photos/59880708@N05/5551882163/ A Pic of the carbs, and I with i had a color tune , on top of that i wish they were attainable with in a reasonable price!, and I have yet to find a unisyn in nz, though I hav beenmaking a little balancing tool, but I havnt managed to find a long enough and big enough clear tube ( ripco and super crap are useless ) and BNT and auto stop dont have, aswell as my usual auto one doesnt have, though i havnt tried bunnings.
ginga4lyfe,
Mar 24, 5:22pm
WRONG, the 2500s has strombergs standard!
ginga4lyfe,
Mar 24, 5:24pm
I havnt put new points in, and have checked for tracing, but it cant do any harm to recheck, there is next to no play in the dizzy shaft, I hadnt checked the little cap carbon stalk thing
skin1235,
Mar 24, 5:27pm
and those are not what I picture a stromberg to be, in fact they look very much like refugees from and old austin princess
skin1235,
Mar 24, 5:32pm
than remove and check the points thoroughly, mid range misfire is more common to incorrect points gap and or condition than valves, on apar with carb mix and balance fail and plug fail
richardmayes,
Mar 24, 5:49pm
Early Triumph 2000s have Strombergs, later model 2000TCs and 2500TCs have SU HS4s or HS6s. It's easy to tell the difference, Strombergs have "CD STROMBERG" written around the top in massive lettering cast into the body of it.
There's no diaphragm in an SU, but one of the 3 screws holding the lid on the float chamber should have a little aluminium tag on it identifying it as an HS4 or 6.
Some very late HS6s have fixed (i.e. non-adjustable) jets just to make things more interesting.
richardmayes,
Mar 24, 5:58pm
I don't know how you'd find out, but don't worry too much about the unleaded on the valves. When the head came off my PI at 200,000 miles for rings & bearings, after 10,000km of pretty fast no-valvemaster driving by me, there was no valve seat recession to speak of. (And PIs have an older-type head that was apparently quite prone to burnt exhaust valves. The later "TC" engines like yours have a smaller exhaust valve to produce faster gas flow through the valve, which supposedly helps reduce this problem. )
ginga4lyfe,
Mar 24, 6:14pm
ok well I just came in after a few minutes of checking over the car and balancing the carbs via the vacuum guage i have connected across the bridge on the inlet manifold the idle is high and wont come down on the one carb, so it definitely needs a new throttle spindle and bush and butterfly, the second one is adjustable and i have managed to balance them via just that one- therefor high idle ( same problem i had pre carb pull off, just no sticky choke ) i tuned the carbs to run slightly rich ( lift pin-idle rises then stumbles ) drove it around the block and. FARK! this thing is a rocket! but! still spitting and firing through the carbs and poping the forwardplunger out the dashpot, so. Im thinking now. abandon the head removal, pull the carbs ( again! ) and replace the throttle spindles, bushes, and butterflys, and hope that its not expencive and fixes my problem! ( in thinking that the wear on the spindles may be causing the lean out at upper range, and new butterfly brings down idle on the carbs more!
skin1235,
Mar 24, 6:21pm
smear a good dollup of heavy grease around that spindle or if you can slide a small oring up tight against the body, even copious wraps of insul tapeand take it for another run, if it improves it then go ahead and change spindles etc, if it doesn't improve it then don't bother, look elsewhere You say front dashpot pops up - therefore the damper effect is not able to work correctlty, tape it down, add thread tape etc, wire the sucker in, find a way to keep it down, then try again, no damper effect and you've got issues beyond a reasonable fix, then get another dashpot, they're not supposed to be able to pop out, they have to screw in and out, it is in effect the main shaft on a shock absorber
ginga4lyfe,
Mar 24, 6:27pm
yeah, I was wandering why the car had thread tape on it to begin with ( before the issues arose ) eh, id still have to replace the butterfly to reduce the idle, so why not do the spindles and bushings anyways!
socram,
Mar 24, 6:44pm
If you would like the cylinder head off my recently sold MGB, it is sitting on the garage floor.In a word, rooted.Previous owner didn't use an additive and a dose of leaded race fuel now and again was too late to save it. Horrendous valve seat recession.If you'd like to buy it, it is yours for a song!I had to get another head for it and had it set up with hardened valve seats so at least the new owner won't need to worry about it.
ginga4lyfe,
Mar 24, 6:51pm
I thought MGB's had 4 poppers! but yeah, thanks for the offer anyways, Ill see how things go
skin1235,
Mar 24, 6:51pm
agree, and how many other older heads have you seen in similar condition!, back then we had to do valve grinds too, no particular brand, some (peoples) cars needed them some others same model didn't while there is potential for seat recession it is not an absolute result, it happens, as it did when we had leaded fuel too
skin1235,
Mar 24, 6:55pm
they could be quite forgiving to bush wear and not hard to adjust for the effects ( the vacumm above cylinder is not greatly effected by the spindle leakage but they tend to run just a little leaner due to more air getting into the throat fix the damper and try again - it will have a far greater effect then surplus air across the jet end
pdc1,
Mar 24, 6:59pm
listen to skin. He has alot of helpful stuff in his comments. The plunger shouldn't come out like that, so sort that. The butterfly shafts didn't happen straight away so I would not expect this to be your problem. I'm concerned how you are balancing them. It may be okay with the Vacuum guage if everything is perfect and you don't have a problem. I'd grab a bit off the end of your graden hose and have a listen to each carb at the same revs. You will get it pretty close like that. As for the fuel mixture, a slight rise in revs and a stutter at idle by lifting pin is probably about bang on, rather than slightly rich.
pdc1,
Mar 24, 7:08pm
I think skin was a little harsh about his statement, but mgb's did this when they were running on leaded petrol as well! I would love to see the tests quantifying the difference of valve seat recession with additives and without. It is not as if it is going to totally stop recession. I'd rather just wait and put valve seats and valves in when necessary
ginga4lyfe,
Mar 25, 7:26am
ok, i just phoned around manukau, and CDL Auto want 157 PER carb rebuild kit, and the kit only suits ONE carb! with no spindle bushes either! , I think ill just order the seperate parts from the UK , though i hate ordering off shore
pdc1,
Mar 25, 8:06am
Don't go spending all that money yet. As skin said work out the problem before you fix it. He mentioned about putting lots of grease around the end of the shafts to see. Also just try taping the plunger in. Has the thread gone on the plunger or the body! What is the plunger thread- plastic or brass! I really think that it will be a combination of the plunger, correct balancing, and a ignition problem that is causing you grieve rather than anything else.
smac,
Mar 25, 8:46am
Bit late on this one.I saw Triumph and fell sleep ;)
Back firing through carbs and mid range power issues has always been plunger/damping issues for me. Wrong spring, wrong oil etc. It has oil right! Poking your finger in the inlet and lifting the plunger and letting it drop, how long does it take! Any resistance/catch points on the way up!
ginga4lyfe,
Mar 25, 11:07am
Oh dont worry im not looking to buy yet, im just browsing for the bestprice, though i still have to replace at leased the throttle plate to bring down the RPM's, but yeah, today i have not had enough chance to work on the car, but i plan to dollob alot of grease on the spindle ends as soon as i get the chance
ginga4lyfe,
Mar 25, 11:10am
Iv never actually checked that, i did check to see that the pistons moved freely inside the pots, but never the return time, but i would imagine that it would be a fairly free falling drop, though i do have 20 weight engine oil in the pistons, the springs though, i have noooo idea how they are supposed to be, all i know is they are long, and squishy, and both are the same
smac,
Mar 25, 11:11am
What makes you think the high idle is definitely the butterfly! They need to do about 4 squillion miles to actually wear. When running, can you poke the butterfly with your finger and make it close! More likely to just be assembled slighty off where it needs to be on the shaft so it hits one side of the inlet before it's closed.
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