Inconsistent starting- won't start sometimes

[edog]

Turns over the engine but doesn't catch all the time. Sometimes it catches and fires for one cycle and dies. And then other times it catches and runs fine. 

The other day I took the carb off to see if i could clean it out, but the previous owner stripped the screws on it and i wasn't able to get it apart. 

What could this be? i'm willing to try to clean the carb if that's likely the issue. I don't have any maitenance experience or knowledge so i'd rather not attempt anything too crazy by myself. 

I will note that it was quite difficult to get the carb off of the engine. I don't think there is a leak on the manifold. I don't know how to check the choke or bystarter.

[scooterfan]

If the screws are stripped, it means the carb will not seal properly and air could be sucked into the carb at certain points. If this happens, the carb will never work correctly.
I think you have no option other than opening the carb, get the holes re-threaded, clean the carb properly, and install slightly bigger screws.

If you don’t sort the carb out first you could easily find yourself running in circles without been able to solve the problem.

[edog]

It's only the head that is stripped, not the threads on the screws. Carb is sealed shut. 

I tried manually-choking the scooter and it started up immediately. Did this by covering part of the air filter box with my hand per the advice of some youtube videos. This makes me think the problem might be the choke, or auto bystarter. How would i figure out if this is the problem?

[eamartin]

Bystarter can be removed and tested.  Disconnect the 2 wires that power the bystarter.   Remove the 2 screws holding the bystarter retainer clip to the carb .  Pull out the bystarter (it may help to twist as you lift upward; there's an oring in there, do not damage it).  Connect the 2 leads to a 12v battery.  the bystarter will begin to heat up and after a minute or two the needle/barrel will begin to extend, probably about 1/8".  If it extends, the bystarter works.  If the needle does not move, bystarter doesn't work.
Another problem could be clogged passage to the bystarter fuel well or clogged idle jet or any number of things.  But if the scooter always starts when you starve it for air, then the problem could very well be inside that carburetor.  Did this scooter sit for any length of time?
Also, which screw(s) is stripped?

[edog]

Thanks, I'll investigate this. I have a feeling it may not be getting power, since it seems to not be working.

2/3 screws on bottom of carb that you would undo to get to the jets are stripped.

[TBR125]

The auto by-starter/enricher functions by allowing additional fuel to the engine during starting and is shut off when the internal wax plug expands and pushes the needle into the passage. It is simply time based, the equivalent of using full choke for every start be it 5 or 95 degrees.

My Solution, bought this back when it was 26 dollars. It replaces the auto choke on kymco 50 and 125GY6.

https://hammerheadperformance.com/manual-choke-for-150cc?matchtype=&network=g&device=c&adposition=&keyword=&gclid=EAIaIQobChMIxZrKtvjt6AIVGa_ICh3v3gi_EAQYASABEgKlJPD_BwE

[eamartin]

Thanks, I'll investigate this. I have a feeling it may not be getting power, since it seems to not be working.

2/3 screws on bottom of carb that you would undo to get to the jets are stripped.

The bystarter only gets power when the engine is running (AC).
Hard to comment about the float bowl screw.  Vise grips might do it.     

[edog]

The auto by-starter/enricher functions by allowing additional fuel to the engine during starting and is shut off when the internal wax plug expands and pushes the needle into the passage. It is simply time based, the equivalent of using full choke for every start be it 5 or 95 degrees.

This is why I'm thinking it might not be getting power. When i took off the carb last week i may have messed with a wire because it worked fine before that, but clearly the engine isn't getting enough gas to start now. probably from the a non-working choke.

[eamartin]

If you suspect a faulty bystarter you can test it.  If you suspect no power to the bystarter, get the scooter running, disconnect the bystarter wires from the power supply wires and test the power supply wires with a meter.

[eamartin]

The auto by-starter/enricher functions by allowing additional fuel to the engine during starting and is shut off when the internal wax plug expands and pushes the needle into the passage. It is simply time based, the equivalent of using full choke for every start be it 5 or 95 degrees.

My Solution, bought this back when it was 26 dollars. It replaces the auto choke on kymco 50 and 125GY6.

https://hammerheadperformance.com/manual-choke-for-150cc?matchtype=&network=g&device=c&adposition=&keyword=&gclid=EAIaIQobChMIxZrKtvjt6AIVGa_ICh3v3gi_EAQYASABEgKlJPD_BwE

TBR, that site lists the part for 150cc.  I see nothing for the 49cc machines.

[TBR125]

After a running part numbers I found that the manual choke did truly replace Kymco Parts 15563 and 15439. I can't remember all the details and sources because this was over 2 years ago. One of those numbers is the auto choke used on I believe all Kymco four stroke carbed bike models. I used that link for my kymco agility and it screwed right on with no adjustments. I will try to load some pics.

Obviously please do your own research before modding stuff like the carb which controls your engine running or not. 

Here's the manual choke.

[TBR125]

Here's a picture of the auto by-starter it replaces.

[TBR125]

And if you want you can cut open your electric choke and replace the wax plug with a choke cable and you have a free manual choke. I built this one when I was 14 but my parents wisely would not allow homemade parts on my transportation at that time. I installed the manufactured choke but tested the jury rigged one and it work perfectly.