TR6 1975 TR6 runs lean

Still trying to figure out why the car is running so lean. Requires the choke to be out about 1/3 or it mis-fires (backfires?). With the choke out, it runs well. Replaced the fuel pump with electric producing 3 psi. Checked the timing (11 degrees), new distributor cap and rotor, electronic ignition. Zenith-Stronberg carbs. Metering needle is set at max rich (full clockwise) on both carbs. Push the choke in past the 1/3 mark and the card misses even at freeway speeds.

Looking at rebuilding both carbs including new o rings on the metering needles.

Any ideas, suggestions, recommendations (other than going to fuel injection). Any and all help is welcomed.

Thanks,
Frank

You might check the rubber carburetor diaphragms for any tears.

Gliderman8 said:

You might check the rubber carburetor diaphragms for any tears.

Click to expand...

Elliot,
Good idea - unfortunately both replaced about 2 months ago. I am thinking that the problem is in the metering needle, maybe not moving correctly. But I would think that would have different characteristics at different rpms.

Am I right that it sounds like a fuel problem, not electrical.

Have you checked to make sure that the metering needle has not come out of the threads on the adjusting screw?

Elliot,
No, I didn't think anything like that could happen. Is there an easy way to check? Easy - of course it is a British car and nothing is really easy. The only think worse is a sailboat (and I can easily give more stories on sailboats - at least there the engine is supposed to secondary).

If your carbs have adjustable needles and if you have the proper needle (mixture) adjustment tool...use it according to directions and turn the allen wrench clockwise. If you can turn it more than 3 and 1/2 turns and still have not come to a full stop...then the needlle carrier has become unscrewed from the needle height adjustment screw.... If you do come to a stop within 3 and 1/2 turns, turn the allen wrench 1and 1/4 turns counterclockwise. That's the middle of the adjustment range...If you still have a problem, it's not because of the needle...it will be in the correct position to get the engine started and continue to run, pending very fine tuning in the future

I couldn't have said it better.... poolboy has given you the instructions; follow them. It only takes a couple of turns counter-clockwise for the needle to disengage from the adjusting screw.

This may lead to the problem. Both carbs from full clockwise went past 8 turns without stopping. I'll pull the metering needle assembly out.

It sure sounds like the needles have come out. Let us know what you find.

No need to pull the metering needle assembly out, but having the air valve out in your hand makes the job easier, IMO
With the air valve removed, push what portion of the needle carrier you see within the air valve up into the air valve while pushing down with the allen wrench as you turn it clockwise...The idea is to reengage those 3 threads between the adjuster and the carrier.

It worked! Front carb definitely was a problem, the rear carb may also have been disconnected. Either way, pulled the air valves on both and made sure they were connected. Once back in place, not a misfire or stutter. Ran beautifully through all RPMs. Tomorrow is a short road trip, about 50 miles round trip. Gives me a chance to check on mpg (seems like it has been drinking fuel). Did show one new problem that I will start a new thread - press on the brake and the rpms increase by 400. Just replaced the non-return valve as it was dropping about 300 rpms when the brake was pressed. For now, the car is running and feels like a Triumph - great feeling.

Thank you for you help, suggestions and patience.

Glad to hear the good news. Enjoy the ride.