I picked up a Downtown 300ABS in nearly perfect condition in late 2015 with 18.170 kms
When driving home I noticed red Voltage charging light lit up. Calling the seller (motorcyle shop) they replaced the defect Voltage regulator free of charge by a new but probably cheap aftermarket unit.
Few months later I started to notice 2 main phenomenon independently from eachother :
1. unexpected idle collapse to 1000 rpm sometimes and then engine stall;
2. unable to start/restart in any circumstances. Once with cold engine in the morning but sometimes with warm engine for example when returning to the scooter after short break or trying to restart immediatelly after engine stall: so not consequently occuring in terms of the cirmumstances.
After restarting attempts always: the battery was dead within a matter of max. 30 seconds to 1 minute making me unable to restart the scooter any longer that day. It will have the highest significance in the story....
The mechanician's assumption was even without mentionning the pre-history that the fast dying battery during the restart attempts (even when the battery was almost few days/week old) makes him guess that I am driving without or with minimal charging for days and weeks cannibalising the reservoir capacity of the new battery. His guess was correct: zero charge. The source was the stator (burnt).He furtherly guessed in advance that the regulator is also defect and knocked out but he can test it optimally built in and only after repairing the stator. Stator was professionaly re-coiled. After re-coiling the next step was to test Voltage regulator in 'life' circumstances. It was also defect, just as he forecasted. 0 charge.
Replacement done and....tadaaaammm: Everything perfect. After numerous similar motorcycle problems from earlier (he says at least 5times per year in his shop floor), hi states that worst quality aftermarket regulator may have caused damage to the stator, too. And in some cases killing the battery in addition...just to have the foam on the cake.
Almost all of his customers with similar problems have aftermarket Voltage regulators built in....Suzuki Burgman, Piaggios the same.
The charging now is between 13,66 and 14,4 during the whole RPM range depending on the RPM and the on board comsumers switched in/off. Bike will start after 2 or max 3 crank revs. Cold and warm the same, no difference.
The problem source of the idle stalls was however unknown even for the mechanician, source was not detected but it seems that it is also belonging to the past: At least I did not experience it since, ridden 600km since. My own amateur assumption: different electro-magnetical characteristics of a damaged stator MIGHT have caused idle problematics but it has not been happening since the reparation. Hurray!
A so called universal/multipurpose regulator has been installed and proved to be high quality and very reliable for bikes with similar or same electrical/electronical characteristiscs like DT300. I must use this, because I only found aftermarket units (Central Europe) from different chinese manufacturers some for around 25€ to 40€......No go zone for me !And in addition this regulator is not the strongest side of the DT300 anyway even if it is coming from the factory's supplier.
I strongly disadvise buying cheap Voltage rectifier/regulators from unknown manufacturing sources.
The failure sympthomes were NOT conspicuous in the beginning making me ride the bike without suspicion but making the Downtown 300 unstartable in an unexpected way hundreds of km-s far away from my home in the hills (you can imagine the transport of the bike and other stuff plus killing my weekend program entirely). !
PS: no Voltage red lights lit up during the whole problem series except when the battery was dead or nearly dead after the numerous attempts on startbutton.
I want to send a big 'thanksalot' to User CROSSBOLT/KARL from the USA for his caring support to get rid of my issue. We learnt a lot from this and discussed this issue to be worth to share with the community.
Greetings Peter
