The Triumph 2000/2500/2.5 Register Forum

Well after getting all 6 cylinders back and running the car up today to full temperture i was still niffed at the smell that was being produced from the exhaust,the richness smell makes me smell and gave me a stinking headache....
So after i was happy with the smoothness i have now removed the carbs today without any dramas so i can tackle these in confort and take a close look at them.
I spoke to Chris witor today who was most helpful and i have placed on order the following
New gaskets,float valves,jets,plain throttle butterflys and on his advise new BFZ needles after me explaining the car has a MM bottom engine with aP.I head and a supersport exhaust and a cam but unknown but it does have some grunt.
So my question is what tips should i take note of when looking at the carbs,i,ve read the workshop manual a few times now to get myself familiar and i find it interesting about the fast idle and throttle idle screws,whats the differance here?
One of the things i want to also acheive is the horrid rich smell disappearing.
Also when i pull the choke out when stone cold,the car starts fine,but it doesn,t actually idle faster with the choke out,it just makes it richer.
Any info or pics to help would be great,not rushing this so want to get it right first time.

With a carb set at the correct mixture, if you were to enrich it manually, initially the engine speed would increase, but enrich it too much, the engine speed would decrease, and the engine would begin to run unevenly.
When the choke is operated to start the engine from cold, the mixture is temporarily enriched to facilitate the cold start. To help with the smoother running of the car on choke, the fast idle cams increase the tick over by rotating the throttle linkage, therefore resulting in a faster tickover whilst the choke is in operation. Without the fast idle cams, the richer mixture would just cause the engine to stall almost immediately.
The basic principle is the same for both SU's and Stombergs.
Adjustment of the fast idle cams is basically turning the stop until there is a slight clearance between the stop and the cam, so that the cam doesn't operate on tick over, but with a slight operation of the choke, the cam moves to the stop and then begins to move the throttle linkage , and increasing the tickover to compensate for the richer mixture.
When re assembling your carbs, make sure the piston falls freely and come to a stop on the bridge with a metallic clunk. Check the jets aren't worn into an oval, because SU needles are biased to one side and this can cause the jet to become oval instead of round, and this can result in an over rich mixture.
I find that when setting up from basics, release all the throttle and choke cables and linkages first, and fully unscrew the idle screws. Make sure the butterflies in each carb are completely closed before retightening the linkage. Then do the same for the choke linkage, (ensuring the choke knob is fully home) so that both carbs operate simultaneously. For a basic setting, I turn the idle screws one full turn from the point they begin to contact and operate the throttles. You can then either turn each idle screw equally, or use a air flow meter to measure the air, flow, or use the old way of a length of tubing to your ear to ensure the 'hiss' is the same.
Then go onto your mixture adjustment!
Hope that makes sense!

Very helpful,thanks i will be reading any posts when i get the parts and rebuild the carbs,replacing the jets worries me abit but i must just take my time
What is best to actually clean the carbs with,and is it correct ATF fluid is best for the dashpots.
The cams i did notice tonight before i removed the carbs are totally missing the stops so thats the main reason the fast idle on choke doesn,t work,but i will adjust these when all refited.

I've always used normal engine oil in the dashpots, but to be honest, I don't think it will make much difference. An oil with a higher viscosity will just give a slightly longer enrichment when you boot it!

Changing the jets on an SU is easy (not so on a Stromberg though!). They should just come out the bottom when the linkage and fuel pipe is removed. While you have them apart, do check the float heights.

It sounds like it's running too rich at present, so set the rebuild carbs to the starting position (in the manual?) and then adjust each one in turn. With practice, this can be done 'by ear/feel' but you may want to play with the 'lifting piston' method. Or a colour tune thingy. Basically, it'll sound OK when rich, but as you go too weak it'll begine to falter, so go back again. I find on modern petrol, you want to run it a bit on the rich side to avoid running on (which I used to get on the 2000).

Good luck!

Cheers,
Mike.

Are 100 thou jets to big?
CW says he might not be able to get the jets to me for Sat as they are coming elsewhere.
But i can pick a pair up from Moss tommorrow as i,am going close to them.
What is the advantage of the yellow dashpot springs aswell?

Remember that if you adjust the throttle settings to get the carbs balanced you will need to release and re-clamp the connecting link, because you cannot alter the individual spindle stops if they are joined together. If you do then they won't open at the same time.

100 thou jet size is I think correct but you'll need to check. I have a Burlen book at home - or you could go and look on their site. They now own the rights to SU and Strombergs (I think) and remake all the bits. Maybe that's where Chris is getting them from. They do rebuild kits and I used one for the Strombergs on the Stag.

The dashpot spring should also be to spec - again from the book I guess. I'll try and remember to look tonight.

Clifford's point is important. You really want to set each carb up on it's own with the throttle and choke linkage disconnected (or unclamped anyway). Then you can set idle speed and mixture for each carb in turn and then reconnect them both.

Cheers,
Mike.

The correct grade of dashpot oil for the HS range of SUs is 20W/50. ATF will surely be much too thin?

Hello SAHtuning,

"What is the advantage of the yellow dashpot springs aswell?"

A yellow spring (part no. AUC1167) is correct for the Triumph 2000 range except for some export cars and is what you should have. I expect that the colour has long since disappeared?

Alec

I stripped the carbs down today,very carefully and took note/drawings of what goes where to help.
So all the new parts arrive tommorrow.
A few things i noticed is that the is 21.3 stampaed on the throttle discs.
Also removing the jet was interesting,i was told it was just a case of undoing the 11mm nut on the base of the float chamber then the screw holding the jet to the choke rod,but thats not how mine was,its a bar from the choke setup down to the jet which passes through the jet and is held in place by a speed clip,you have to remove the whole choke setup to release the rod otherwise you can,t remove the jet from the base of the carb,very annoying,it does show a screw in the workshop manual so i guess this might be an earlier version,also been told that 76 cars have waxstat jets,mine doesn,t.