Quote:
Originally Posted by dmw244gl
Thanks for the information and the break down pdf.
i think its the top cover of the carb that has the crack, im waiting to find out.
but cant see a part number in the pdf for that.
the mechanic does thing its the jet
"my judgment the base jet is worn ..making it impossible to control fuel delivery ..with the timing not correct and the Dwel angle changing all the time (base screw cross threaded in distributor) not holding the points correctly in position"
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The jet in the carb is in the lower body of the carb and from what you said earlier, the needle had come out of the piston - the piston rises and falls in relation to airflow into the engine and manifold depression, hence the CD in the carb designation denoting "Constant Depression".
You need to get the ignition correct before you start meddling with the jet and needle in the carb. Most common cause of the dwell angle changing all the time is wear in the bushes in the distributor (that's
bushes NOT brushes!) that the main distributor shaft runs in. It's a common problem with those era of Bosch distributors.
If some muppet has cross-threaded the contact breaker screws in the dizzy base-plate, you need new screws minimum. Then remove the base-plate and re-tap the holes (correct size) and hope that cures it, if not, you need a new base-plate.
That said, your better option for the long term would be to obtain a dizzy from a later 240 with electronic ignition (Hall Effect) with the sensor in the dizzy, the ignition amp module and convert it, no need to worry about contact breakers then or a varying dwell angle. This is a fairly common upgrade/modification (i believe Alan has it on his RB) so there should be information somewhere on the forum exactly how to do it.
Failing that, a reconditioned dizzy.
A question though - is your mechanic monitoring the dwell angle with the engine running while trying to adjust the carb? If so he's over-analysing things as the dwell angle naturally changes with engine speed/load courtesy of the mechanical advance weights and also the vacuum advance mechanism. Dwell angle should be checked/adjusted while cranking the engine, not with it running.
Also if he's not familiar with that particular carb, he could be adjusting it the wrong way from the start.. The throttle butterfly is factory set and shouldn't be altered, there is an idle air volume screw to adjust the idle speed and then the mixture is adjusted with another screw.