4 stroke engine running help

GeorgeG4

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Hello all

George from Maine. Getting chilly here.
I have a 4 stroke 49cc engine ( no idea on the brand, bought of eBay a few years back) on a beach cruiser type bike. Ran great, but this year would not run right. Cleaned carb etc. no luck. I did some research and found that the stoke carbs don’t last. So I bought a manifold and a clamp on NT style 2-stroke carb. (It’s Chinese) The bike at least works now. But it has a bog when trying to accelerate hard from idle. Will actually die out if the throttle is held open. Feather it and it is ok. I know it’s only 49cc but it seems lacking power and crispness. I’m sure I need to reject. Probably a bigger jet? Running lean? What size jets for these carbs? Best place to get jets?

Also after reviving the bike up the throttle hangs. Takes a good few seconds for the engine to come back down to idle. Thoughts?

Looking to just get it running reliably and best that I can.

Thank you all for the help.

I’ll try to post pics to show you what I’m working with.
 
Here are a couple of pictures.
 

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You should ditch that carb and order a JRL Bofeng carb. Its a much better desighn than that carb.
 
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You should ditch that carb and order a JRL Bofeng carb. Its a much better desighn than that carb.
Really? Looks very similar. What is better about it? Is it any more tunable than the one I have? The one I have only has an idle screw.
 
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Really? Looks very similar. What is better about it? Is it any more tunable than the one I have? The one I have only has an idle screw.
Yes, the bofeng is tunable by raising and lowering the "C" clip on the needle valve like the stock NT. but It also has an emulsion tube while the one you have does not.
 
The BoFeng is also built much thicker where the carb flange fits over the intake tube as well...That area is known for breakage when tightening the NT because it is too thin.

The Stock NT carburetor.

61a5R2yKT9L._AC_SY355_.jpg


The much improved and sturdier BoFeng with emulsion tube inside that is NOT in the NT, (improved throttle response through all ranges).

616jGJ0ukBL._AC_SX425_.jpg


Needle valve showing the "C: clip that needs to be adjusted for your altitude, if I remember correctly you are at about 1000 ft elevation, if that is the case, you want to start in the middle groove on the needle...There are 5 grooves on the needle...Then adjust idle from there.

Slide Needle Grooves.JPG
 
The BoFeng is also built much thicker where the carb flange fits over the intake tube as well...That area is known for breakage when tightening the NT because it is too thin.

The Stock NT carburetor.

View attachment 200106

The much improved and sturdier BoFeng with emulsion tube inside that is NOT in the NT, (improved throttle response through all ranges).

View attachment 200107

Needle valve showing the "C: clip that needs to be adjusted for your altitude, if I remember correctly you are at about 1000 ft elevation, if that is the case, you want to start in the middle groove on the needle...There are 5 grooves on the needle...Then adjust idle from there.

View attachment 200108
Alright i will get one of those carbs and see what happens.
 
The BoFeng is also built much thicker where the carb flange fits over the intake tube as well...That area is known for breakage when tightening the NT because it is too thin.

The Stock NT carburetor.

View attachment 200106

The much improved and sturdier BoFeng with emulsion tube inside that is NOT in the NT, (improved throttle response through all ranges).

View attachment 200107

Needle valve showing the "C: clip that needs to be adjusted for your altitude, if I remember correctly you are at about 1000 ft elevation, if that is the case, you want to start in the middle groove on the needle...There are 5 grooves on the needle...Then adjust idle from there.

View attachment 200108
This the correct carb? It’s on eBay.
 
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