I guess there's a leak but where?

[iani]

I struggled to get my CO to give a positive reading yesterday, DaveB came round today and we reset the Needles, and tried adjusting them but again we could only get a CO of 1.0 at the richest setting. In case the Gunsons gauge was playing up we fired up Dave's car and checked it, the readings were spot on so it looks like I must have an air leak somewhere? The revs don't drop at all with the oil filler cap removed, however, with a vacuum gauge fitted we get a constant strong vacuum reading. I had changed the cam cover gaskets last night so as one was leaking I took them off and have refitted with Silicon this time, now no leaks. I took the carb pedestal off and have fitted a new O ring, the engine breather hoses are all new this week and tight. The car has been misbehaving over the last couple of days, it cut out on me a couple of times and restarted after around 15 mins with no visible problems. I had changed the coil and tried a second new one when the car cut out to no avail, we checked the coil today and it's showing 6V correctly. We're out of ideas now, I took the car for a run this afternoon, 40 miles including a couple of stops, it ran great, better than it has for a while, I just don't understand why the CO is so low with the carbs running as rich as we can make them. Any ideas chaps?

[stag157.7]

I struggled to get my CO to give a positive reading yesterday, DaveB came round today and we reset the Needles, and tried adjusting them but again we could only get a CO of 1.0 at the richest setting. In case the Gunsons gauge was playing up we fired up Dave's car and checked it, the readings were spot on so it looks like I must have an air leak somewhere? The revs don't drop at all with the oil filler cap removed, however, with a vacuum gauge fitted we get a constant strong vacuum reading. I had changed the cam cover gaskets last night so as one was leaking I took them off and have refitted with Silicon this time, now no leaks. I took the carb pedestal off and have fitted a new O ring, the engine breather hoses are all new this week and tight. The car has been misbehaving over the last couple of days, it cut out on me a couple of times and restarted after around 15 mins with no visible problems. I had changed the coil and tried a second new one when the car cut out to no avail, we checked the coil today and it's showing 6V correctly. We're out of ideas now, I took the car for a run this afternoon, 40 miles including a couple of stops, it ran great, better than it has for a while, I just don't understand why the CO is so low with the carbs running as rich as we can make them. Any ideas chaps?

check the height of the jets below the bridge
looking for 2mm to the outer edge ,if not you may need to tap them down a fraction, sounds like its running lean

alan

[iani]

check the height of the jets below the bridge
looking for 2mm to the outer edge ,if not you may need to tap them down a fraction, sounds like its running lean

alan

We started with them flush Alan, getting a negative CO reading there, took in full turn, then another, got to 3.5 turn in the end, can't go any further?

[stag157.7]

We started with them flush Alan, getting a negative CO reading there, took in full turn, then another, got to 3.5 turn in the end, can't go any further?

measure the jet height

not the needle


alam

[AlanD]

i think Alan is talking about the Jets Ian, you are talking about the needles, if this helps i took mine down 3.5 turns and then another quarter after that, this time i just took her in and had her tuned, an hour and 60 quid lighter but she is running like a dream now

Alan

you beat me to it Alan

[iani]

Alans'

I get the point about the jets but, not having the carb in bits in front of me, only the ROM, I don't see the adjustment process listed. I have owned twin CD150's in the past on GT6's and the jets were adjustable there from the base, on the Stag carbs this is just a blanking plug. If I take the float chambers off can I adjust the jets from below?

Ian

[AlanD]

no Ian, they tap in and out, it;s the only way to adjust them, Alan is the best one for the carbs, he's the expert, if you log onto the ' buckeye triumph website' they have a break down of the carbs on there, this should help you out a little.

try this link to there site Ian

http://www.buckeyetriumphs.org/technical/Carbs/CarbsIII/CarbsIII.htm

Alan

[iani]

Thanks Alan, I should point out that these carbs were reconditioned two years ago and the jets haven't been touched since, I don't see why the jet settings should have changed? I've just about had enough of this car right now, it's not been an enjoyable month so far :-)

[Firept]

Ian.
You've probably tried this but seal off the pipe to the air intake flap valve, and the other one is the Carb pedestal just make sure its not drawing in air from the central fixing nut / stud.
Is your ignition electronic or points as some of the electronic ones need 12Volt at the coil, although it does sound like a fuel /air problem.
Only other one is the inlet manifold gaskets, Its messy but may be worth it, get some of the old fashioned red Redex put it in a flexi spout oil can and with the engine running squirt the Redex around the inlet manifold where it mates with the heads and watch the exhaust it will go white smoke if there is a leak, its getting it under the manifold is the problem . It's very messy but it will clean up.
lastly don't discount the Carbs as being faulty given the state of some of the rubber components that are being sold in the UK nothing would surprise me, I replace both of the strut top mount cover grommets about 2 years ago as the old ones just looked a bit shabby I looked today and both have started to disintegrate and you can hardly say those are highly stressed components.
Best of luck dont give up you will get it sorted.

Paul.

[tibbsy]

Reading this was very interesting iam having problems with pair of recon carbs I have just purchased, a tuning specialist in
Plymouth is going to try and sort mine in the next week, so will let you know what he finds, if it helps.

TIBBSY

[DaveB]

Ian,

DON'T GIVE UP !!!!!!! I'm convinced this is something simple..

The fact that the needles went over 3 turns with very little affect on the CO suggests there is still an inlet side leak somewhere. There is a chance that the inlet manifold gaskets have sealed well around the waterways but there is an inlet port leak. Paul's suggestion of Redex should confirm this.

speak soon

cheers

Dave

[flying farmer]

When I first rebuilt a set of Strombergs I made the mistake of measuring down to the recess in the centre instead of the outside edge and had the same problem.

The difficulty I had was getting the both the jets to the identical correct height, it was all too easy to tap it too far.

I found the simplest solution was to grind down a spare tappet shim so it covered the top of the jet and then used a wide punch so when tapped it would contact the alloy housing and prevent the jet knocking in too far, it saved having to take the carbs off again.

I used a 100 thou shim which is about 2.5 mm thick, supposedly a bit too much, but it put my needles smack in the middle of their adjustment range when set correctly so I was happy with that.

Neil

[iani]

Thanks chaps, I will try the Redex test as suggested by Paul, I didn't rebuild these carbs, they were rebuilt by Andrew Turner and whilst I have had some issues with them he does know how to assemble carbs, the jets look to be 2mm below the bridge from a visual check this morning. I don't get how a non adjustable jet could move anyway, I've been running with these for the last couple of years without this issue, an inlet leak seems much more likely.

[len]

hi
i had a similar problem last year, emmisions almost non existant ! great for the Mot but not so good for the car,
i took it to Faversham Classics, they were puzzled and spent about 2 hours fiddling with carbs and then changing plugs,leads etc,
eventually after spraying carb claening spray everywhere we had a flash fire and there it was a .... leak in the inlet manifold !
i took it away and fixed it , took it back for a check and would you believe perfect emmisions.

its not always what you think it is !
just a thought
Len

[wilf]

Disable the intake air preheat system by pulling off the vac pipe to the actuating valve on top of the air intake (and blocking the pipe off to stop a vac leak) as I have found the thermo controllers can go wrong and strommies don't like hot intake air.