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Some of you may have followed this saga on various other threads, but I'm starting a new one.
Quick history:
After I got hooked on scooters a couple of years ago and mrs72 commandeered my scooter, I got one of my own. I picked an oddball scooter quite on purpose, a "Genuine Stella Automatic". These scooters are a result of a weird history between Piaggio/Vespa, an Indian manufacturer called LML, and Genuine Scooter Company who really only import and re-brand Asian scooters for the US market. Without going into all of that, suffice to say a Stella Automatic is a mildly modernized Vespa PX with a significantly more modern 4-stroke 125cc engine and CVT in place of the old Vespa's 2-stroke/manual setup. LML, the manufacturer, went out of business in 2019, so this rare scooter is basically orphaned in terms of support.
My first Stellauto ran fine and was a lot of fun for the short time until it nuked its starter ring gear and some nice gentleman in Oklahoma gave me a nearly new one that had been sitting for 8 years to replace it. Now I have my second '14 Stellauto and after bringing it back to life, I rode it for most of a year trouble free until parking it mostly at the end of 2022, when it wouldn't come back from winter this past spring. It's been mostly unridden since early spring.
The problems I recently dealt with are boring and you can look at them in the other threads if you really care, but finally with a freshly cleaned tank and cleaned carb and new pulley in place, the scooter starts reliably now and I've been riding it daily for a few days now. But it has some kind of running problem that I am hoping to sort out in public view on this thread.
The issue is inconsistent running under load at higher rpms. Ever since I got this with 38 miles on it, it has had the same range of issues. Hunting and inconsistent idle, surging while under cruise, and generally iffy running. Now it has gotten to where it really just won't rev above about 5-6k rpm under load and that means a max speed of about 40mph. And if it sits idling like at a long stop light, it nearly stalls under rough idle conditions and then really doesn't want to go when it's time to move.
My current theory is that most of these oddball problems are due to the Dellorto "ECS", or "Electronic Carburetor System". It's a half measure between EFI and carbs, with the intent of meeting Euro smog regs without having to actually do EFI. Essentially it's a carb fitted with a throttle position sensor, an O2 sensor in the exhaust, a little air solenoid valve that meters extra air into the carb to lean it out, and an ECU to control it all. The ECU takes input from the crank to calculate RPM and has a mapping not unlike EFI systems to provide a mapped mixture across throttle/rpm range. It supposedly uses the O2 sensor input at idle. It's a black box that cannot be tuned. Oh, it also serves as the ignition controller/ignitor, and is rumored to do some ignition timing, but there is no kind of knock sensor so it's not interactive. I am guessing just a static advance map based on throttle and rpm.
While I was using the scooter regularly before all of the recent problems, I had disabled part of this ECS by removing the air solenoid hose and plugging the port on the carb, so the carb would just run max enrichment according to the jetting. Looking at the spark plug makes it clear that it was running very rich all the time, which I guess is to be expected. When I did the recent repairs, I hooked the air solenoid back up, and now it has these weird running issues again.
This 24mm Dellorto ECS carb is unique to this particular scooter and like one or two other Peugeot scooters only sold in Europe. Dellorto doesn't list it in their parts catalog. LML didn't even put it on any of their other 4T engines. It's very difficult to find parts for this carb, and tuning information is nonexistent. But there are jillions of GY6 scooters, pocket bikes, go-carts, you name it, all over the world, which all use 24mm Keihin PD24J carbs or clones of those carbs. So my next move is going to be trying one of these PD24J carbs in place of the ECS carb.
The PD24J is slightly larger overall than the Dellorto, and the Dellorto carb currently touches the fuel tank on one side when fitted, so there's a chance I may have to fab up another intake tube with a bend in it to scoot the bigger carb over a little bit to clear the fuel tank. Also, the stock airbox has a curved rubber hose that connects to the carb which is not going to fit pretty much any way we slice it, especially if I have to scoot the carb over. I may have to come up with some other solution, including ditching the airbox entirely, which I really don't want to do. I think I can likely make the throttle cable work, perhaps having to trim some of the housing. The big thing is that the Keihin carb has no way to use a throttle position sensor, so either I have to rig something with some kind of linkage or just do without it. I have ridden the scooter before with the TPS disconnected (inadvertently) and it seems to run fine this way, so besides putting up with a flashing ECS light (kind of like a check engine light), it might work ok.
The goal of fitting an easy to service, abundant-parts and current production carb has enough benefits to make this fab and tinkering exercise worthwhile. I also ordered a jetting kit, but I figure the stock jetting for a typical 125cc GY6 is probably a good enough start. If I wind up going the no-airbox route and using a cone filter, then popping the carb off to rejet is a cinch.
This weekend I plan to do this swapping, in hopes to get the Stellauto running like she should so I can ride with mrs72 on her new(ish) Kymco scooter for the whole of the fall. While I'm goofing with it, if I can find the appropriate piece of exhaust tubing to make a patch, I may cut out the little catalytic converter and bypass it. I actually think it may be clogged, probably from me running it too rich for too long, and maybe that's half of the running problems.
Quick history:
After I got hooked on scooters a couple of years ago and mrs72 commandeered my scooter, I got one of my own. I picked an oddball scooter quite on purpose, a "Genuine Stella Automatic". These scooters are a result of a weird history between Piaggio/Vespa, an Indian manufacturer called LML, and Genuine Scooter Company who really only import and re-brand Asian scooters for the US market. Without going into all of that, suffice to say a Stella Automatic is a mildly modernized Vespa PX with a significantly more modern 4-stroke 125cc engine and CVT in place of the old Vespa's 2-stroke/manual setup. LML, the manufacturer, went out of business in 2019, so this rare scooter is basically orphaned in terms of support.
My first Stellauto ran fine and was a lot of fun for the short time until it nuked its starter ring gear and some nice gentleman in Oklahoma gave me a nearly new one that had been sitting for 8 years to replace it. Now I have my second '14 Stellauto and after bringing it back to life, I rode it for most of a year trouble free until parking it mostly at the end of 2022, when it wouldn't come back from winter this past spring. It's been mostly unridden since early spring.
The problems I recently dealt with are boring and you can look at them in the other threads if you really care, but finally with a freshly cleaned tank and cleaned carb and new pulley in place, the scooter starts reliably now and I've been riding it daily for a few days now. But it has some kind of running problem that I am hoping to sort out in public view on this thread.
The issue is inconsistent running under load at higher rpms. Ever since I got this with 38 miles on it, it has had the same range of issues. Hunting and inconsistent idle, surging while under cruise, and generally iffy running. Now it has gotten to where it really just won't rev above about 5-6k rpm under load and that means a max speed of about 40mph. And if it sits idling like at a long stop light, it nearly stalls under rough idle conditions and then really doesn't want to go when it's time to move.
My current theory is that most of these oddball problems are due to the Dellorto "ECS", or "Electronic Carburetor System". It's a half measure between EFI and carbs, with the intent of meeting Euro smog regs without having to actually do EFI. Essentially it's a carb fitted with a throttle position sensor, an O2 sensor in the exhaust, a little air solenoid valve that meters extra air into the carb to lean it out, and an ECU to control it all. The ECU takes input from the crank to calculate RPM and has a mapping not unlike EFI systems to provide a mapped mixture across throttle/rpm range. It supposedly uses the O2 sensor input at idle. It's a black box that cannot be tuned. Oh, it also serves as the ignition controller/ignitor, and is rumored to do some ignition timing, but there is no kind of knock sensor so it's not interactive. I am guessing just a static advance map based on throttle and rpm.
While I was using the scooter regularly before all of the recent problems, I had disabled part of this ECS by removing the air solenoid hose and plugging the port on the carb, so the carb would just run max enrichment according to the jetting. Looking at the spark plug makes it clear that it was running very rich all the time, which I guess is to be expected. When I did the recent repairs, I hooked the air solenoid back up, and now it has these weird running issues again.
This 24mm Dellorto ECS carb is unique to this particular scooter and like one or two other Peugeot scooters only sold in Europe. Dellorto doesn't list it in their parts catalog. LML didn't even put it on any of their other 4T engines. It's very difficult to find parts for this carb, and tuning information is nonexistent. But there are jillions of GY6 scooters, pocket bikes, go-carts, you name it, all over the world, which all use 24mm Keihin PD24J carbs or clones of those carbs. So my next move is going to be trying one of these PD24J carbs in place of the ECS carb.
The PD24J is slightly larger overall than the Dellorto, and the Dellorto carb currently touches the fuel tank on one side when fitted, so there's a chance I may have to fab up another intake tube with a bend in it to scoot the bigger carb over a little bit to clear the fuel tank. Also, the stock airbox has a curved rubber hose that connects to the carb which is not going to fit pretty much any way we slice it, especially if I have to scoot the carb over. I may have to come up with some other solution, including ditching the airbox entirely, which I really don't want to do. I think I can likely make the throttle cable work, perhaps having to trim some of the housing. The big thing is that the Keihin carb has no way to use a throttle position sensor, so either I have to rig something with some kind of linkage or just do without it. I have ridden the scooter before with the TPS disconnected (inadvertently) and it seems to run fine this way, so besides putting up with a flashing ECS light (kind of like a check engine light), it might work ok.
The goal of fitting an easy to service, abundant-parts and current production carb has enough benefits to make this fab and tinkering exercise worthwhile. I also ordered a jetting kit, but I figure the stock jetting for a typical 125cc GY6 is probably a good enough start. If I wind up going the no-airbox route and using a cone filter, then popping the carb off to rejet is a cinch.
This weekend I plan to do this swapping, in hopes to get the Stellauto running like she should so I can ride with mrs72 on her new(ish) Kymco scooter for the whole of the fall. While I'm goofing with it, if I can find the appropriate piece of exhaust tubing to make a patch, I may cut out the little catalytic converter and bypass it. I actually think it may be clogged, probably from me running it too rich for too long, and maybe that's half of the running problems.
or diary. Mebbe I'm too dense to get it.
Maybe I'll just say "I fixed it" and leave it at that.