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Triumph TR6 - Weber carb trouble

A couple of weeks ago I made a decision I now may be regretting. Having been told that my ZS carbs were in dire need of rebuilding, and after hearing a couple of high recommendations for the dual Weber (downdraft) setup, I made the leap - bought the kit and installed it. Actually pretty easy to install, and it ran reasonably well for being "right out ot the box." I then decided to have a professional do the tweaking. After trying to smooth things out, my mechanic then asked me "what the #%$!!$!, and told me the carbs are jetted all wrong. Yes, they were jetted for a TR6, but I was never asked, and never thought to tell the seller about my location, i.e. Colorado (~5,000 ft. msl). Bummer.

Question - am I hosed? Do these need to be re-jetted to lean out, and is this worth the effort? Will the dual Weber setup function as desired (i.e. smooth and increase performance) if my car is "at elevation", or am I wasting my time?

About the only comment I've hear so far it to make sure I feed the water supply to the carbs(not done yet), but this seems more of a cold weather benefit.

Thanks for your thoughts.
Ed Armbuster

i have spent alot of time with fine tuning the webers and they are great,, if you don't have the coolant running through the manifold, the fuel won't atomize
( even in warm weather ) or if the thermostat isn't getting the engine up to 180 degrees it is almost impossible to get them jetted. all they want to do is dump raw fuel into the engine. email me back and maybe i can give you a little help..john

I, too, am having Weber DOWNDRAFT carb problems on my TR6. I bought the Weber downdraft setup "apart" but was toild the car ran fine...however, I suspect it didn't as it doesn't run fine with this setup on it ( runs OK with stock carbs, but not with the Webers.
I have mostly pretty technical questions. Here they are...hopefully someone can help:

1. can someone tell me what the best probable jetting should be for this setup? Idle jets, mains, emulsion tubes, and air correctio jets for the Primary circuit? Also for the secondaries?

2. do I use more ignition timing with the Weber setup than the 4 degree ATDC stock setup?

3. What is the correct FLOAT level for these carbs?

4. is there a good/better/best tech manual that will help sort through this setup?...I've already got a Haynes Weber book, but most of these books don't suggest a base level starting point that's anywhere specific to a TR6.

I've torn the Webers down and know what's there now for jets, but suspect the previous owner had changed things, so not sure what it should be. They run rich at idle, and I can't even begin to get the secondaries open without the engine cutting out and mis-firing badly. If I accellerate just on the primary barrells, it goes ok ( still not right..)but at least it's driveable, but it's frustrating to drive it like that ( basically at half throttle, max ).

Thxs for any help!


I went down two sizes in jets, and it seems my problems are solved. I'm in CO and the carbs came from sea level, so this solution made sense. Sorry I cant help with your more technical questions.

Ed A.
Ed A.

contact are the best Webber people in New England!
ray campbell

My 1976 runs very strong with webers.
But I also have electronic ignition,old stock 150hp UK cam(from Bp Northwest)& Lucus Sport Coil.
Plus engine overhaul with new .20 over pistons.
Timing runs about 20 degrees BTDC.
Better to tune with vacuum guage at intake manifold.
john myers

This thread was discussed between 25/07/2000 and 02/09/2000

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This thread is from the archive. The Live Triumph TR6 BBS is active now.