The issue is turbo cokeing not anything to do with choking. Cokeing is when the there become hard charcoal lile deposits that for in the turbo oil return system. This causes the bearing to spew out oin into the exhaust, creating lots of smoke and draining the oil reserve. When this occurs the turbo oil sump needs to be removed & cleaned as well as blowing out the oil return lines.
I had the same problem until I discovered that the last person who overhauled the carbs put the enriching circuits (chokes) on the wrong carbs, which made them upside-down and they worked backward. They were on all the time until you wanted to start the engine, then pulling the choke cable turned them off. Getting them correctly oriented solved the problem.
You will probably need to reset the idle needle after you correct the chokes.
Jim, thank you for your reply. I finally found the problem. On the left carb the choke valve was installed 180 deg wrong. That seems to be a position where the engine is running normal with out choke but if you close the throttle and pull the chock, there is no fuel supply for the left two cylinders. I also recognized that the holes in the disc valve are very small in comparison to the size of the jet which is located in the carburetor bowl. The engine starts now a lot better and runs with the choke pulled, however, i feel the cold start performance could be improved if the two holes of the choke disc are enlarged a little bit. Since the engine was new i never suspected something like that, but now it works.
Thank you every body for your replies!
There are several things to be careful of when rebuilding a Bing 64 carb and you can damage it or put several thing in backward. You wouldn't know some of these without being taught or shown. I recommend that anyone doing a carb rebuild go to someone who is qualified to have it done to watch the first time if you are going to do your own maint. many of us have carbs sent to us to do and it isn't as bad as you think.
An example:
The better carb rebuild kit is $349 with everything in the carbs replaced (both carbs)including the floats. The next good kit is $249 (both carbs) and that's everything except the floats. If the floats don't need replacing after an exam then you good to go which is the majority of us. The smallest and in my opinion least substantial kit only replaces the "O" rings (just to incomplete) for around $45-$65. Labor varies a lot. Any where from
$45 hr to $95 hr. Time also varies.
You can get them rebuilt many times with a 24 hr turn around and a 1 hr labor charge, plus parts and shipping.
So if you shop around you may see $249 for the kit, $50-$60 for labor (1 hr) plus shipping and a 1 day turn around. Then with this kit you have some brand new carbs completely cleaned and except for the floats brand new parts ready to go for the next life cycle.
Roger Lee LSRM-A & Rotax Instructor & Rotax IRC Tucson, AZ Ryan Airfield (KRYN) 520-349-7056 Cell
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