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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Need Advice, can't keep an idle (intermittently) approaching or at a stop with New Amal 276's
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<blockquote data-quote="Old Bill" data-source="post: 132518" data-attributes="member: 1683"><p>Mark, some thoughts; replace HT Leads readily available from car parts shops, ensure good seal between manifold and carb, plumbers ptfe tape perfect for this, ensure carbs are as vertical as possible (if tilted it will affect float height). Are the new carbs set as per the old units in respect of throttle cutaway, jet sizes and needle position? From what you have stated it sounds like a weak mixture but other issues can cause a similar effect. Achieving perfect carb balance is only possible with vacuum gauges and don't forget the two stage rule, balance at idle and at raised slides to synchronise cable lift. As Bill Thomas has written the idle speed will vary considerably from cold to hot engine temperature. In Know thy Beast Eddie Stevens tells us that the rear cylinder needs a richer main jet, interesting theory. My experience has been that the rear carb sometimes requires raising the needle one notch or a richer slide either a 3.5 or 3 in extremes but if using a richer slide return the needle to mid position and set the slow idle just after start up when you can open the throttles with no choke and no spit back, when warm the motor will probably idle a little quick but at least it wont stall at an inappropriate time! Finally remember that as other guys who know far far more than l have said no two Vincents are the same and yes they are temperamental even in the hands of experts like greg, hey ho...</p></blockquote><p></p>
[QUOTE="Old Bill, post: 132518, member: 1683"] Mark, some thoughts; replace HT Leads readily available from car parts shops, ensure good seal between manifold and carb, plumbers ptfe tape perfect for this, ensure carbs are as vertical as possible (if tilted it will affect float height). Are the new carbs set as per the old units in respect of throttle cutaway, jet sizes and needle position? From what you have stated it sounds like a weak mixture but other issues can cause a similar effect. Achieving perfect carb balance is only possible with vacuum gauges and don't forget the two stage rule, balance at idle and at raised slides to synchronise cable lift. As Bill Thomas has written the idle speed will vary considerably from cold to hot engine temperature. In Know thy Beast Eddie Stevens tells us that the rear cylinder needs a richer main jet, interesting theory. My experience has been that the rear carb sometimes requires raising the needle one notch or a richer slide either a 3.5 or 3 in extremes but if using a richer slide return the needle to mid position and set the slow idle just after start up when you can open the throttles with no choke and no spit back, when warm the motor will probably idle a little quick but at least it wont stall at an inappropriate time! Finally remember that as other guys who know far far more than l have said no two Vincents are the same and yes they are temperamental even in the hands of experts like greg, hey ho... [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Need Advice, can't keep an idle (intermittently) approaching or at a stop with New Amal 276's
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