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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
HD Decompressors (Solenoid)
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<blockquote data-quote="andrew peters" data-source="post: 166038" data-attributes="member: 3776"><p>The (latest) HD electric decompressors are 'wired' through the ECM and the starter solenoid so allow a brief few revolutions of the motor before spark and fuel are introduced.. it's all computer controlled so not quite applicable to us. Also the HD electric decompressors 'exhaust' through a drilling into the exhaust port,(more for emissions) again not applicable to us here.. So I guess you have the manual pop-off type decompressors, burning gasses are escaping before the motor shuts the decompressor. So we need to cut the spark on initial start up.. On the earlier HD Shovelheads with electric start the problem was getting the motor to spin fast enough to actually fire and run, early Norton electric start bikes had a similar problem but they were using the same Prestolite starter as Harley in the mid 70s... A 'fix' was to modify the start/run switches on the rightside handlebar. The idea was the starter would spin the motor up faster (without the coil having power) and once the flywheels had plenty inertia you switched the ignition coil on, the motor fires and runs! In our case, the decompressors should shut as compression builds so by the time you switch the ignition (coils) there no burning fuel escaping. This all happens quite quickly of course however it does require a two thumb operation, start button and ignition switch, or some clever wiring with delay relays... A;ways when we solve a problem we find we've created two more! good luck</p></blockquote><p></p>
[QUOTE="andrew peters, post: 166038, member: 3776"] The (latest) HD electric decompressors are 'wired' through the ECM and the starter solenoid so allow a brief few revolutions of the motor before spark and fuel are introduced.. it's all computer controlled so not quite applicable to us. Also the HD electric decompressors 'exhaust' through a drilling into the exhaust port,(more for emissions) again not applicable to us here.. So I guess you have the manual pop-off type decompressors, burning gasses are escaping before the motor shuts the decompressor. So we need to cut the spark on initial start up.. On the earlier HD Shovelheads with electric start the problem was getting the motor to spin fast enough to actually fire and run, early Norton electric start bikes had a similar problem but they were using the same Prestolite starter as Harley in the mid 70s... A 'fix' was to modify the start/run switches on the rightside handlebar. The idea was the starter would spin the motor up faster (without the coil having power) and once the flywheels had plenty inertia you switched the ignition coil on, the motor fires and runs! In our case, the decompressors should shut as compression builds so by the time you switch the ignition (coils) there no burning fuel escaping. This all happens quite quickly of course however it does require a two thumb operation, start button and ignition switch, or some clever wiring with delay relays... A;ways when we solve a problem we find we've created two more! good luck [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
HD Decompressors (Solenoid)
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