Iv been fideling with my triumph 2500tc, she has been running very rich so i dove in to balance and tune the carbs, so after i found out that tuning the adjusting screws only made it burn richer and no leaner AND i could not get the idle lower than 900rpm, I decided to pull them off give them an examination clean them and bolt them back together,and now I have another problem, I put them back together the same problems exist still but now, she is back firing REALLY badly, both out the exhaust and the carb, I have re done the compression tests and have found that the cylinders are now all at 150psi and no manner of fideling witht he ign tappet clearance or carb idle and mixture has fixed the problem// so im stummped, I had my old uncle come round and have a look at it, we then proceeded to double check everything, we cannot find any manifold leaks, and as far as we know everything is 100% as it should be, yet. its still back firing and plooming out dark grey smoke, the same is indicated on the plugs that it is burning rich, but all of them are working as all of them came out dry ( and F'n HOT ) after a run. so. ahh. HELP! I dunno what could have changed so dramatically since yesterday, she was driving around fine, just a little rich
thejazzpianoma,
Mar 12, 3:28pm
O.K so I havn't read about any previous posts regarding this so ignore if its out of turn.
1. Are the carbs standard and jetted standard!
2. Does it have a standard cam!
3. Have you checked the ignition timing and made sure its advancing etc as it should!
4. The choke is adjusted correctly and not stuck half on since reassembly!
5. Have you given the plugs a good clean up!
6. Have you cleaned out the carb jets and if/when you did this used air and not a bit of wire to clean them!
thejazzpianoma,
Mar 12, 3:31pm
Also. I am not a Triumph expert (only ever owned one) so am I right to assume we are running SU carbs here!
If they are SU carbs you havn't by chance changed the oil in them have you! A difference weight of oil in an SU will upset things.
BTW whichever carbs you are using I would suggest doing a google and finding some kind of manual or detailed explanation on how they work and adjusting them (google the type of carb not the car and you will likely have more luck). That sort of thing is usually easy to find and well worth while.
ginga4lyfe,
Mar 12, 6:17pm
if they fit and do the job well, get me some for free, and i will. Not that i know what DCOEstands for!
saki,
Mar 12, 6:27pm
ATF could be a bit thin and not giving the require damping.
saki,
Mar 12, 6:35pm
ging try a 10/40 and see if there is a difference if there is then you can play around, a single 20 wt would be the ideal, make sure there is the correct level of oil.
ginga4lyfe,
Mar 12, 6:54pm
haha, yeah I made sure the carbs were the last thing i had done, its just annoying that these problems have arisen like they have
ginga4lyfe,
Mar 12, 6:58pm
I doubt that will cause this problem, I had the same oil it has now in the pistons for a few weeks now and it ran fine then, its only after i cleaned the carb ( to try remedy the fast idle and rich mixture problems ) that it had started happening
thejazzpianoma,
Mar 12, 7:35pm
This may not be causing all your problems but it is important to run the right consistency oil for correct running. I havn't played with SU's for years so not sure what/how atf fluid compares to what they should be running but would suggest you look into this further.
thejazzpianoma,
Mar 12, 7:37pm
ginga, having read through your great responses I think you are on the right track and I also agree with what others have said. BUT before you do anything give those plugs a really good clean or replace them if they are older.
I have been caught out in exactly your position wondering why I couldn't tune some side drafts and it took a while for the penny to drop that my 5 minutes old spark plugs had already gummed up.
That car BTW was running a high powered electronic ignition system so no doubt the effect on your Triumph would be even greater.
Best of luck, have a good read up on SU's there is plenty on the net on how they work and tuning them. They are a great carb and offer a lot of advantages if you understand how they work and how to tune them properly.
ginga4lyfe,
Mar 12, 7:48pm
Cheers Jazz, I had thought of cleaning them before poping them back in, but they just didnt look all that gummed up, they are a week old of so themselves, but it may very well be that the plugs are keeping there heat and causing the backfires, or other problems, So first thing tomorrow ill be pulling them out and cleaning them up
jmma,
Mar 12, 7:51pm
Check your leads are on the right firing order!
ginga4lyfe,
Mar 12, 8:35pm
Yup, 3 times, it helps to double and triple check the basics and not let the " nah im sure" mind set kick in, rookie mistakes are normally the ones to keep you running in circles like this, but not this case -_- , I wish i could "magic" it fixed, but I also wish we had seafoam in NZ, I hear it really helps Su's that are carrying on like this!
ginga4lyfe,
Mar 13, 9:49am
well I found that no 1 cylinder plug wasnt firing, I swapped it with a known good one ( I always knew that keeping the old plugs was a good idea! ) and now its definatly firing on that cylinder, But its still idling rough as guts and back firing through the exhaust and carbs, I think its time i got to pickapart and got a head that i spotted at the wreckers, either that. or. I buy a known good triumph engine for 200 and then pay however much the shipping is for it to come from canterbury to Manukau, Btw. could this be going n like it is now since i did recently change from 91 to 96! ( I only changed because it was pinking!)
Fuel pressure too high - pushing petrol through the carbs! Do these things have a regulator of any type!
Vacuum line to dizzy not replaced (if they have one).
Are you certain that all of the linkages are on correctly, not holding the carbs open (forgive me if SU's don't work that way, I'm more familiar with Holleys & a small amount on Webbers)
Completely out of curiosity - have you tried it with the air box back on! (even though in theory I would think they box being off would make it leaner not richer).
I assume you aren't putting the Gull ethanol mix stuff in it. No sure, but I would expect that to not be nice to an old Triumph.
Removing, cleaning and replacing the carbs has probably upset all the throttle balance. Also I hate to think what sort of tune it was running to make it accept 91 octane, they really aren't built to run on jungle juice!
The only adjusting screws on top of your carbs are the stops that limit how low the idling speed goes.
(1)With the engine running, make sure the two throttles are balanced and opening exactly together using a suction gauge. IIRC the adjustment is done with the clamps on the throttle shaft between the carbs. (2) Get it running as lean as you can with the adjustment nut on the jet underneath. My dad's trick to check when you've got it about right, is that if you have a good smooth idle then when you push up the little spring-loaded plunger on the bottom of one carb, the engine should splutter and almost die, but not quite. (3) Check your plugs frequently as we've found this is the most reliable way to verify if she is running rich, lean, or 'other'. Check all 6 of them, if the back 3 are black and the front 3 look good for example, then straight away you'll know the back carb is rich.
(4) Don't give up! SU carbs were invented right back at the dawn of motoring, and they were still there in the 1980s, because until EFI really got going there really wasn't anything better.
richardmayes,
Mar 13, 11:19am
PS: as per extrayda's second point, take the lids off the float chambers and make sure the little ball cock valve is clean and free to open and shut as the float falls and rises. It works exactly like the valve in your toilet cistern.
ginga4lyfe,
Mar 13, 1:47pm
I cant ballance them as the car is atm, the engine is moving too much, and im not going to blow out an ear drum using the pipe method, how ever the choke and accelerator linkages to open at the same time,I cant get it to run any leaner, and lifting the pin seams to do nothing with how its running, and i practicly have just given up I just dont get it, the compression shows all even, the timing is 100% spot on, the gaps on the points are correct, the plug gaps are correct,I assembled the carb correctly, the linkages are setup correctly, and still the thing is running like its missingbut all plugs ARE firing, -_-
extrayda,
Mar 13, 2:45pm
bad coil causing weak spark etc (my favourite suggestion !).
illusion_,
Mar 13, 6:32pm
Twin choke side draught Weber. They would make it go like the clappers. Unfortunately they are rarely cheap, and almost never free, and bank managers just dont seem to understand
richardmayes,
Mar 13, 7:08pm
If the only thing that has changed since the last time it ran correctly is the carbs , then it's unlikely that the problem is anything other than the carbs.
[EDIT: unless the person who tuned it for 91 octane did a really good job, and found non-standard needles that suited 91 better!]
And it's all coming back to me now.sorry I've been driving a PI for a while!
Take all of your plugs out, see if it's rich or lean. Then at least you'll know which way you need to wind the jets before you try again.
Have a play with the two jets until you know how many turns of the adjusting nut each one is above the bottom or down from the top, (hopefully they are more or less the same.)
To balance the throttles, loosen the two clamps on the throttle shaft, then start the engine. Then measure the suction in the intake to each carb with a suction gauge and adjust those idle screws on tops of the carbs until you have equal suction on both AND a the lowest steady idling speed you can get. Then do up the clamps on the throttle shaft.
Now it's time to get your mixture right, by adjusting the jets up or down to make it richer or leaner. My dad & I aren't really mechanics, so we use a trial and error method which is probably not how it's taught in the best of schools, but you get there in the end. If you can get a nice smooth idle and a good quick response to a light stab on the throttle, without any puffs of black smoke out the exhaust, then you've probably got it pretty right.
Be prepared to go back to step one and wind the idle speed down a bit with the idle screws, if the idle speeds up and gets smoother as you start to get your mixture closer to where it should be.
ginga4lyfe,
Mar 13, 8:11pm
i only wish i had a suction guage,were can i buy one and how much roughly! it would stop alot of guess work for me!, also, Another thing i have been told to do is replace the Condenser, it may be kicking the bucket at higher RPM, really I may aswell buy new points leads and a coil too
jmma,
Mar 13, 8:19pm
If you haven't got a vac guage you can use a piece of hose held to your ear and put the other end by carby throat, not as accurate, but it works (o:
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