Author Topic: Engine bogs down and almost stalls when turning the throttle  (Read 2350 times)

dotshouse

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OK, so after I figured out the auto cock gas flow issue and got the scooter to fire right up, which it will still do, when I give it gas, even after it idling / reving for 5+ minutes, when I turn the throttle it will rev up briefly then start to bog down. Even trying to feather the throttle, I can't get it to stay at high rpm's.

I had just had the carb off and completely apart, blew out every port and pulled the jets and blew them out in both directions. I pulled the spark plug and cleaned and rechecked the gap. I'm sure everyone will say carb, which it probably is but has anyone else had this problem and able to fix it?

I'm not sure if there is a way to check if the choke is working, if that might be what is causing the problem.

Any help is appreciated.

BettinANDlosing

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Re: Engine bogs down and almost stalls when turning the throttle
« Reply #1 on: May 25, 2015, 07:53:31 PM »
If your idle jet is clogged, it'll take sending a wire physically through to clear it, the hole is so small air alone usually won't clear it. The idle jet is your issue, take it out and look for light though it or blow it and see if it flows.
2002 Kymco B&W 300; MRP 78MM "300CC", Naraku cam, Yoshimura rS3 exhaust, 17g Sliders, Yellow torque spring drilled airbox, stock carb #115 main #40 pj.

2001 "Yamaha" Zuma AKA MBK Booster; MHR OverRange, Dellorto 19mm BHBG, Polini "big" intake, RS-3 Rear shock, Stock cylinder.

dotshouse

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Re: Engine bogs down and almost stalls when turning the throttle
« Reply #2 on: May 25, 2015, 09:00:23 PM »
Thanks for the feedback. I presumed I'd be taking it apart again unfortunately. I meant to say in my post that I blew everything out with carb cleaner and was pretty comfortable with how well I got all the ports and jets to get cleaner to flow through them but since my only other real recourse is to take it to a shop, I'll pull the carb and go through it one more time.

How reliable are the electronic auto chokes? I did see a youtube video of a guy doing a carb cleaning and he mentioned putting a manual choke on his. I'm pretty good about taking stuff apart and putting it together but I am far from a motor head so any help is appreciated.

I'll have to find that video again, it showed which of the two jets inside were which. I'll tear it completely apart and go through it again but will make sure I spend extra time on the idle jet.

Thanks

BettinANDlosing

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Re: Engine bogs down and almost stalls when turning the throttle
« Reply #3 on: May 25, 2015, 09:56:27 PM »
Thanks for the feedback. I presumed I'd be taking it apart again unfortunately. I meant to say in my post that I blew everything out with carb cleaner and was pretty comfortable with how well I got all the ports and jets to get cleaner to flow through them but since my only other real recourse is to take it to a shop, I'll pull the carb and go through it one more time.

How reliable are the electronic auto chokes? I did see a youtube video of a guy doing a carb cleaning and he mentioned putting a manual choke on his. I'm pretty good about taking stuff apart and putting it together but I am far from a motor head so any help is appreciated.

I'll have to find that video again, it showed which of the two jets inside were which. I'll tear it completely apart and go through it again but will make sure I spend extra time on the idle jet.

Thanks
The chokes are pretty good, I don't see too many fail but they do every now and then. Easy to test. Take the two screws out that hold it. Gthen you'll see a needle type thing inside a brass cylinder. These move down to block the air and fuel passages. When you start the scooter voltage is applied to the wires and melts a wax solenoid in the choke which let's a spring push down the plunger and needle. You can test it by simply using jumper cables to the positive and negative battery terminals, green wire to - and the yellow to + but I've found it to work either way. Watch the brass plunger, it should go Down, relative to how the carb sits. I like to use sharpie to give a good line to judge it's movement. It takes about 60 seconds to fully extend.
2002 Kymco B&W 300; MRP 78MM "300CC", Naraku cam, Yoshimura rS3 exhaust, 17g Sliders, Yellow torque spring drilled airbox, stock carb #115 main #40 pj.

2001 "Yamaha" Zuma AKA MBK Booster; MHR OverRange, Dellorto 19mm BHBG, Polini "big" intake, RS-3 Rear shock, Stock cylinder.

herrspoot

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Re: Engine bogs down and almost stalls when turning the throttle
« Reply #4 on: May 26, 2015, 01:40:47 AM »
Hate to say, but it probably is your idle jet, and yes, lots of times that one needs a physical cleaning. I know with the ignition system on my like, if the battery is low or dead it will present symptoms like that. Do you have to kick start it or can you use the starter? If you can't use the starter, try charging up your battery.
2012 Like 50 2t
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dotshouse

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Re: Engine bogs down and almost stalls when turning the throttle
« Reply #5 on: May 26, 2015, 07:25:52 PM »
Thanks for the additional info. Actually, the battery is toast. I put the trickle charger on it for a day and a half and finally got a warning light on the charger that there is a problem with the battery. I was planning on picking one up yesterday, just didn't make it. I've just been hooking jumper cables up to my car.

I'll go grab one and getting it charging before I pull the carb again.

Thanks again.

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