VT 21 carb confusion

HP engines (Hirtenberger, AG Austria) tech support. Owned by RJL Industries since 1990

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VT 21 carb confusion

Postby Martin » Mon Jun 11, 2012 2:24 pm

After setting the high speed needle with the idle needle just clear from the spray bar, the engine runs overly rich when throttling back and dies before reaching half throttle. To get any low speed running at all, the idle needle has to be turned in so much that the engine leans out when throttle is opened (needle never exits the spray bar).
No tank pressure is used. Fuel mix, glow plug and tank location according to Mecoa’s manual.
I get the impression that the spray bar doesn’t reach long enough into the carb body (approx. 0.5mm into the 4mm throttle bore), or that the idle needle has wrong tapering or length. However, the carb is all Austrian original. Any suggestions, can the spray bar be adjusted in any way?
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Postby MECOA » Sat Jun 16, 2012 1:47 pm

Try unscrewing the main needle 1 turn. The idle needle always protrudes into the end of the spray bar. If it clears the spraybar end when barrel is open it is way too far on the rich side.
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