4 stroke keeps stalling

[giveearholdtongue]

Hi guys. New to everything motorized bikes. Just finished building this about a week ago. I've looked around, but can't seem to find an answer to why my 4 stroke keeps stalling. I uploaded a video of what happens. As soon as I let off the throttle, it stalls out. And I've pushed the idle screw pretty far out--you can see in the video that the back tire is spinning once I lift it up. Maybe carb needs to be tuned? Also, you can hear a whining/grinding sound coming from the engine. I am thinking transmission. Maybe more grease? Let me know what you guys think.

So that my problems are clear, I'll reiterate:
- the engine stalls out, and I can't imagine the idle should be pushed out as far as it is, nevermind farther
- whiny, grinding sound coming from the engine (possibly transmission)

video link:

 

[Chainlube]

Post a picture of each side of your motor so we can see what you have on the bike. What motor do you have? What cab are you running? Etc..

 

[giveearholdtongue]

Post a picture of each side of your motor so we can see what you have on the bike. What motor do you have? What cab are you running? Etc..

https://www.ebay.com/itm/4-Stroke-Top-49CC-Gas-Petrol-DIY-Motorized-Bicycle-Bike-Engine-Motor-Kit-Scooter/164267354185

That's the link to the exact kit I bought. Pretty standard china kit. Thanks for the response.

edit: links to pics:

IMG_1524.HEIC

drive.google.com

IMG_1525.HEIC

drive.google.com

 

[Solux]

https://www.ebay.com/itm/4-Stroke-Top-49CC-Gas-Petrol-DIY-Motorized-Bicycle-Bike-Engine-Motor-Kit-Scooter/164267354185

That's the link to the exact kit I bought. Pretty standard china kit. Thanks for the response.

edit: links to pics:

IMG_1524.HEIC

drive.google.com

IMG_1525.HEIC

drive.google.com

Nice clean build bud. I like that you ditched the tensioner and just cut to length.

The Whining noise might just be the clutch since it's centrifugal clutch. But not 100% sure since I can't hear it.

That's a weird one, maybe air or fuel restriction? Try taking out the air filter and running it.

Could also be a carb issue, restricting gas. Maybe the jet, or float.

 

[darwin]

Pull the supply fuel line off of the carb. Does fuel consistently pour out? Not in drops but a whole tube flow. If so your fuel tank, petcock and filter are eliminated as issues. I see you have an air mixture screw on your carb and it looks capped off by a brass plug. Behind that plug is your adjustment screw. That needing adjustment might be it. Your starved for fuel by the sound of the video. Maybe your carb bowl isn't filling up with fuel because of a needle/float issue.

 

[giveearholdtongue]

Took apart the carb and fixed the problem. All of the set screws were way too tight and I had the expulsion tubes connected instead of free to expel gas. Explains why the air box would fill with gasoline occasionally. Snapped head off a set screw, though, so will have to get it out and replace. Ideas?

And if you watch the video with the volume up, you can hear the noise that is made by the engine. It happens at 6 seconds and lasts until the engine dies. That whiny, grindy sound. A little like scratching a vinyl record. Going to look into the noise further tomorrow. Well, today now. Thanks guys.