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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Poor starting on new Amal and BTH Magneto
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<blockquote data-quote="greg brillus" data-source="post: 42143" data-attributes="member: 597"><p>Hi there Minivin, Ok first off...as David Dunfey has pionted out in an earlier post, the twin spark BT-H will not need so much overall advance due to the burn in the cylinder occuring much faster, so as David said you may only need 19 or 20 degrees. If the mag has variable timing, then on start and slow running it's most likely the timing will be somewhat retarded in the region of 10 to 14 degrees past TDC this will make starting an issue. If it is a fixed timing mag, then it will start but be inclined to kick back. On the carb side of the equasion, I have fitted a few of these new 229/289 Shadow/Comet carb's and have found every time that the slow running is always too lean, requiring more use of the choke slides than normal just to keep it running. If the choke is lifted too early, the engine tends to cough and spit back through the carb.....the cure i've found is to fit a number 3 1/2 slide and an air cleaner ( which helps, and should be used anyway...) if the 3 1/2 slide is unavailable, i just machine 30 thou off the bottom of the original number 4 slide, reassemble, and then the engine is much happier.....and easier to start. This i have found on 7 new 289 carbs fitted to a Comet, a Rapide and two Shadows.....perhaps it has something to do with our modern fast burning poor atomising fuel available to us these days. Original leaded fuel seemed to last forever, but this modern junk is good for about 3 months at best....Oh, my wife just loves the smell of stale fuel on my hands if i walk in the house.......NOT...!!! Cheers for now......Greg.</p></blockquote><p></p>
[QUOTE="greg brillus, post: 42143, member: 597"] Hi there Minivin, Ok first off...as David Dunfey has pionted out in an earlier post, the twin spark BT-H will not need so much overall advance due to the burn in the cylinder occuring much faster, so as David said you may only need 19 or 20 degrees. If the mag has variable timing, then on start and slow running it's most likely the timing will be somewhat retarded in the region of 10 to 14 degrees past TDC this will make starting an issue. If it is a fixed timing mag, then it will start but be inclined to kick back. On the carb side of the equasion, I have fitted a few of these new 229/289 Shadow/Comet carb's and have found every time that the slow running is always too lean, requiring more use of the choke slides than normal just to keep it running. If the choke is lifted too early, the engine tends to cough and spit back through the carb.....the cure i've found is to fit a number 3 1/2 slide and an air cleaner ( which helps, and should be used anyway...) if the 3 1/2 slide is unavailable, i just machine 30 thou off the bottom of the original number 4 slide, reassemble, and then the engine is much happier.....and easier to start. This i have found on 7 new 289 carbs fitted to a Comet, a Rapide and two Shadows.....perhaps it has something to do with our modern fast burning poor atomising fuel available to us these days. Original leaded fuel seemed to last forever, but this modern junk is good for about 3 months at best....Oh, my wife just loves the smell of stale fuel on my hands if i walk in the house.......NOT...!!! Cheers for now......Greg. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Poor starting on new Amal and BTH Magneto
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