Well this saga continues to drive me up the wall, and now I'm more confused
than ever. Someone please help. I'm not a carb expert, and everything I've done
has been by the book. And at this point I'm at a loss as to what's going on.
Here's the scenario....I'm using the Haynes carb manual...
I've got a TR250. When I got it it had matched 3385 ZS carbs with B1AF
adjustable needles. I verified that both bowl jets are fine, throttle shafts
are fine (no leaks there), air valves, dampers and needles are OK. However, it
was running really lean. Adjustment on the needles to a full rich position
didn't seem to do much good based on the valve lift test. It always started to
slow and stall. So, I rechecked for vacuum leaks somewhere and found nothing
except the PCV (EGR?) line that connects to the air cleaner. When it is
plugged...engine speed drops down to a comfortable 1800 RPM.
So, I changed out the needles for a pair of B2Y needles in non-adjustable air
valves and found the following symptoms:
Once its warmed up, with the slow idle screw backed out of contact with the
throttle cam it idles at about 1800 to 2000 RPM. This with the choke cam on its
closed stop.
In this state, quick goose of the throttle drops RPM to about 1000 immediately
but recovers quickly to previous.
Lift test results in RPM drop dramatically and usually stalls out.
Also, if the choke is pulled when warmed up, the engine balks and dies. Now I'm
really confused.
What should I look for next?
Anyone ever run into this before? What should I do?
Thanks everyone for the help!
Mark
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