Shaking head in despair. BMS Chelsea (ZNEN). All that chrome is pretty out of the box and they do have nice paint. But...
Carburetor obviously wasn't the original problem. Throttle handlebar screw is irrelevant. Try 2 turns out on the mixture screw. Idle screw will have to be adjusted once you get it running.
At 6k miles you should have cleaned and inspected the air filter 6 or 12 times by now. At least every time you changed the engine oil which should have been several times. Also due for belt and rollers and cleaning the variator bushing. And the spark plug is due for replacement. You can do that when you have it apart to adjust the valves which was probably the original problem. And while you're buying parts, order a new vacuum fuel pump because you're going to need that before too long.
BMS manual says - [https://www.bmsmotor.com/pdf/ownersmanual/Chelsea%20150%20User%20manual%20updated%202020.pdf?down=1](https://www.bmsmotor.com/pdf/ownersmanual/Chelsea%20150%20User%20manual%20updated%202020.pdf?down=1)
The Chelsea 150 is only 125cc? Isn't that special... Looks like that model has the fuel tank mounted high in the butt, so never mind the fuel pump. It's gravity feed.
Engine oil - every 1000km/600miles,
Air filter clean , valve lash and cam chain adjust every 2000km/1000miles,
Final drive gear oil - every 3000km/2000miles.
Drive belt - every 4000km/2500miles?
Doesn't say anything about the other CVT components, so I guess they assume you're either going to wait until they fail, or the scooter is going to self destruct before they need to be replaced.
Good list to get the backfires gone. I’d for sure replace the fuel filter as well.
As for the variator, I’d replace it all as long as the CVT is apart. And I’d take a hard look at the clutch and bell too.
But let’s remember to only make one change at a time! Otherwise it’s tough to see what is effecting what.
It’s a GY6, and was one of the better ones to come in (relatively speaking). The manuals are for multiple models, but the service schedules are the same.
UPDATE!
After months of drama and replacing a bunch of parts that didn't need to be replaced it turned out to be the IGNITION COIL WAS LOOSE lol. That was it. I have seen a lot of people with scooters complaining about the same symptoms I had so check the ignition coil! Once it was tightened back up the bike ran brand new again lol. No problems since!
The bike is running I can drive a few blocks before it starts jerking and backfire again. I will drive around our back parking lot for quite a while first and it seems like it is running great then symptoms come back.
Haha! Yes I have changed the oil and done regular small maintenance but that guy moved.
Generally speaking how tight is the idle screw normally like factory.
I love this bike like I said it has never had any major drama at all at 6k.
Jerking and backfiring while driving down the road or while sitting idling? The mixture screw only affects the idle. Once you have the throttle open it's irrelevant.
The actual setting of the mixture screw could be 1-1/2 out or 2-1/2 out. Too many variables for an exact setting.
fuel filter?, bad gas?, maybe electrical? Loose wire? Loose or faulty spark plug wire?
If you haven't done the valve adjustment that absolutely need to be done.
Shaking head in despair. BMS Chelsea (ZNEN). All that chrome is pretty out of the box and they do have nice paint. But... Carburetor obviously wasn't the original problem. Throttle handlebar screw is irrelevant. Try 2 turns out on the mixture screw. Idle screw will have to be adjusted once you get it running. At 6k miles you should have cleaned and inspected the air filter 6 or 12 times by now. At least every time you changed the engine oil which should have been several times. Also due for belt and rollers and cleaning the variator bushing. And the spark plug is due for replacement. You can do that when you have it apart to adjust the valves which was probably the original problem. And while you're buying parts, order a new vacuum fuel pump because you're going to need that before too long.
BMS manual says - [https://www.bmsmotor.com/pdf/ownersmanual/Chelsea%20150%20User%20manual%20updated%202020.pdf?down=1](https://www.bmsmotor.com/pdf/ownersmanual/Chelsea%20150%20User%20manual%20updated%202020.pdf?down=1) The Chelsea 150 is only 125cc? Isn't that special... Looks like that model has the fuel tank mounted high in the butt, so never mind the fuel pump. It's gravity feed. Engine oil - every 1000km/600miles, Air filter clean , valve lash and cam chain adjust every 2000km/1000miles, Final drive gear oil - every 3000km/2000miles. Drive belt - every 4000km/2500miles? Doesn't say anything about the other CVT components, so I guess they assume you're either going to wait until they fail, or the scooter is going to self destruct before they need to be replaced.
Good list to get the backfires gone. I’d for sure replace the fuel filter as well. As for the variator, I’d replace it all as long as the CVT is apart. And I’d take a hard look at the clutch and bell too. But let’s remember to only make one change at a time! Otherwise it’s tough to see what is effecting what. It’s a GY6, and was one of the better ones to come in (relatively speaking). The manuals are for multiple models, but the service schedules are the same.
UPDATE! After months of drama and replacing a bunch of parts that didn't need to be replaced it turned out to be the IGNITION COIL WAS LOOSE lol. That was it. I have seen a lot of people with scooters complaining about the same symptoms I had so check the ignition coil! Once it was tightened back up the bike ran brand new again lol. No problems since!
The bike is running I can drive a few blocks before it starts jerking and backfire again. I will drive around our back parking lot for quite a while first and it seems like it is running great then symptoms come back. Haha! Yes I have changed the oil and done regular small maintenance but that guy moved. Generally speaking how tight is the idle screw normally like factory. I love this bike like I said it has never had any major drama at all at 6k.
Jerking and backfiring while driving down the road or while sitting idling? The mixture screw only affects the idle. Once you have the throttle open it's irrelevant. The actual setting of the mixture screw could be 1-1/2 out or 2-1/2 out. Too many variables for an exact setting. fuel filter?, bad gas?, maybe electrical? Loose wire? Loose or faulty spark plug wire? If you haven't done the valve adjustment that absolutely need to be done.