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Post by ogkillaz94 on Jul 19, 2020 5:02:28 GMT -5
Hello everyone,
This will be my first ever post on this forum and I'm happy to have found this community of people who like to work on scooters as well.
I own a Kymco Agility 50 12'' with a GY6 engine.
I recently put a new 47mm BBK in it with a 47mm cylinder head (which needed to be replaced anyway).
So the problem I'm dealing with now is sputtering that occurs when I open the throttle to about 1/2 to WOT.
I have noticed that getting the scooter to start requires me to open the throttle quite a bit, I already tried using main jets 85-90 which resulted in the same thing. And once the engine is running I have to keep the throttle open otherwise it just dies.
Now when I took the bike for a spin it ran okay with about 1\4 throttle, and when I try to go faster the engine will sputter a couple times (with sputtering I mean that it makes a sputtering sound and it wont move for a second or two) and once it stops sputtering it just accelerates like nothing happened. I did not go WOT for more than a couple seconds because I was afraid of permanent damage so I don't know how well it performs and all that.
The reason I started this thread is because I couldn't really find good info out there, so if there is already a thread about this exact problem I apologize.
But anyway, this thread will be used as a notebook to keep track of how it goes and also to update people who are dealing with a similar issue.
So if you have suggestions, please feel free to write down below.
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Post by mikehailwood on Jul 19, 2020 7:12:44 GMT -5
More info please. How did it start and run before BBK installation? What carb is on it? What air filter setup?
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Post by ogkillaz94 on Jul 19, 2020 7:59:25 GMT -5
More info please. How did it start and run before BBK installation? What carb is on it? What air filter setup? With the original 49cc it ran alright since 2007, I never had this sputtering problem until now. But it would start very easily during cold times with the kickstart, in the hot weather it would usually take a couple more kicks. The carb, the air filter and everything is still original. I have also taken a look at the valves, I set both intake and exhaust at .05mm (which is factory recommended) but I've heard that the exhaust valve could be set at .1 mm instead. So I will try this but I don't think it will help. I also just checked the petcock by sucking on the vacuum line and there was a steady flow of fuel coming out of the other tube. I gapped the spark plug which was too small, but its now at .7mm. Next I will check the carb by taking it apart completely because I have a feeling that it could be clogged or something. |
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Post by GrumpyUnk on Jul 19, 2020 8:20:46 GMT -5
When you open the throttle, some carbs use an accelerator pump to squirt raw fuel into the intake. A lever alongside the throttle lever on the carb works a small pump on the bottom rear of the carb. If the lever is mal-adjusted, it won't squirt. That leaves a pause or stumble as the air will move quickly into the engine, but the larger mass of liquid fuel will take a bit longer to get moving, so it gets a LEAN mix on throttle-up.
Take a look at the linkage where the throttle cable connects. Next to it is where the lever - thin and long- resides. As you move the throttle open, you will see the lever pushed/pulled so it tends to push down on the shaft sticking out of the accelerator pump. The lever can be bent to insure it is moving the pump shaft when the throttle shaft starts to turn.
tom
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Post by mikehailwood on Jul 19, 2020 9:53:42 GMT -5
More info please. How did it start and run before BBK installation? What carb is on it? What air filter setup? "Next I will check the carb by taking it apart completely because I have a feeling that it could be clogged or something." Please record the jet numbers when you dismantle the carb. |
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Post by tortoise2 on Jul 19, 2020 10:42:59 GMT -5
tried using main jets 85-90 Does the main jet needle seat protrude into the throttle bore? Service manual reference.  |
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Post by ogkillaz94 on Jul 19, 2020 10:58:37 GMT -5
When you open the throttle, some carbs use an accelerator pump to squirt raw fuel into the intake. A lever alongside the throttle lever on the carb works a small pump on the bottom rear of the carb. If the lever is mal-adjusted, it won't squirt. That leaves a pause or stumble as the air will move quickly into the engine, but the larger mass of liquid fuel will take a bit longer to get moving, so it gets a LEAN mix on throttle-up. Take a look at the linkage where the throttle cable connects. Next to it is where the lever - thin and long- resides. As you move the throttle open, you will see the lever pushed/pulled so it tends to push down on the shaft sticking out of the accelerator pump. The lever can be bent to insure it is moving the pump shaft when the throttle shaft starts to turn. tom SOLVED I wish I could kiss your forehead! You just saved me a lotta trouble here. I took apart my carb from the scooter and took off the bowl. I found the accelerator pump but I wasn't able to press it down as it was covered in rust. So I took the pump apart and noticed it was full of what I guess is old gasoline. I cleaned the parts and put it back together and tested the pump by filling the bowl with some water, and it was squirting again. I just took it for a spin and there is day and night difference. However it does sputter very minimally when I pull the throttle quickly so I think some more cleaning will fix this rather small issue. But this is what fixed my problem for anyone who is/will be going through this same issue. Pictures: drive.google.com/drive/folders/1iiC0PWcPKsZ0sKjHTd-aHATBPalrL_ot?usp=sharing |
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Post by mikehailwood on Jul 19, 2020 13:33:35 GMT -5
"Next I will check the carb by taking it apart completely because I have a feeling that it could be clogged or something." Please record the jet numbers when you dismantle the carb. I have an Agility 50 with a 72cc bbk as well. What jets are you currently running? |
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Post by ogkillaz94 on Jul 19, 2020 15:23:38 GMT -5
I purchased an entire bag of main jets ranging from 70 to around 100 a while back. Right now it has an 88 jet in it, however I have yet to find the right jet. Although the jet size you need could be about the same as mine, you should always tune it yourself as the environment you live in could be different than mine. |
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Post by mikehailwood on Jul 19, 2020 16:13:51 GMT -5
I understand that. How about the slow jet size?
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Post by ogkillaz94 on Jul 19, 2020 17:01:56 GMT -5
I understand that. How about the slow jet size? The idle jet is still stock. I might change that as starting the scooter requires me to hold the throttle a bit, but I need to do some research on that. |
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Post by Mech Warrior on Jul 20, 2020 11:59:53 GMT -5
Glad you fixed it brother. It's always nice to hear good news!  |
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