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Need help diagnosing fuel mix problem

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ADW said:
.. 1/6 turn of the idle screw takes you from rich to almost correct back to rich ---- while leaning out the mixture! What's up with that? Something else must be coming in to play.
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Sure sounds like a bent or damaged mixture needle, or maybe a bit of flotsom in the screw port.... On some DGV's, there is also an o-ring on the needle that could be messing with you.

Back to your original post - if the back 3 plugs are always black, this is likely not just an idle issue.

Other thoughts - An airflow restriction on the back carb (choke plate, air filter?) immediately comes to mind. And even if these are brand new carbs, I would definitely pull the main and idle jets on both carbs to make sure they are the same on the 2 carbs. Hey, you should know what they are, anyway, now that you're a weber guy. I also would check the float settings on both carbs to make sure they are set the same as well. If when you pull the covers off, the fuel level in the bowls is significantly different......
 
Liking Eric's suggestion of checking the float settings. From the last info re: rich to almost right and back to rich, it seems the thing is transitioning off of the idle circuit to somehow get fuel from the mains.

And just because the things are "new" doesn't necessarily mean they're both correct for the app. You may want to remove and compare the various jets one-at-a-time, front-to-rear...

If you're reluctant to bend the float tabs, swap the carb top lids and see if the "problem" follows the lid?
 
Poolboy was kind enough to stop by today and show me how to use a stethoscope to synch two carbs. My carbs were in synch according to a converted ZS synch tool but in fact they were not in synch - back carb had a faster idle than the front carb. Solving this problem and setting the idle mix to the same on each carb then fine-tuning from there the using the stethoscope worked a charm. My TR6 has never idled or run as smooth as it does not. Thanks again Poolboy and all those that helped diagnose this problem.
 
:laugh:
 
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