Newby Question

[Buddy Boy]

Hey yall I'm new to the motorized biking community and I have a question for ya. So i just got a 49cc 4 stroke engine on amazon and at the beginning the engine was running great and started so easy, But for the past few days it hasn't been starting and when it does it runs very weakly like sputtering. What could be wrong with it?

 

[darwin]

Tried looking for a carb schematic to help explain better but no go. You need to clean the carb it sounds like. 1st see if you have an air mixture screw on the carb or a brass plug covering one. That adjustment might be out of whack. If it has one start at 1.5 turns out then fine tune it. If that doesn't do it next I'd clean the idle jet located under the black plastic idle adjustment screw. It will remove by twisting it out and gently pulling. You need a small wire like from a wire brush to poke through the hole on the bottom, it's tiny. Be careful while removing to not rip the oring or damage it. Reinstall and see how it runs. Some lubricant while removing/installing can help out a lot.

 

[Sidewinder Jerry]

Let's start with the most basic question, are you using a 100% gas? This has nothing to do with octane level. It means there isn't any ethanol being put in the gas.

 

[Chainlube]

After a few heat cycles the valves will need to be adjusted. .15mm intake and exhaust.

 

[Wrench]

In cool weather it started easy and ran great, in hotter weather it's hard to start and runs not so good.
It just might need the air fuel mix screw adjusted.

 

[michael whiteman]

After you get the idle screw adjusted properly you'll want to modify your air cleaner by drilling additional holes in the cover face to allow more air into the filter element. Readjust the idle mixture and check the valve clearances. If you then discover your engine runs smoother and pulls harder from mid to wide open throttle with the choke lever set in the half closed position you'll have to increase the size of your main jet. They come with a #54 which is an 0.021 opening. I drilled mine out to 0.024 which made an improvement but proved to be not quite enough.

Decide for yourself if you want to copy me, but know this, all Huayi crabs run lean to comply with EPA standards. There are some
u-tube videos showing how to clean these carbs which are worth watching. Today I enlarged my main jet to 0.026 and it now pulls really hard all the way to W.O.T. with the choke completely off. Two other things: I do not use the stock air cleaner and I ran the crankcase vent hose into a hole in my seat tube. I didn't want those fumes being sucked back into my engine. I run E85 regular gas.

 

[michael whiteman]

The valve clearances for a 142-F engine are 0.004 intake and 0.006 exhaust set COLD.
I have 3 sets of feeler gauges, and I don't know why I thought to check them against my dial micrometer, but what a surprise !!
They were no way close to what was marked on them. Use a Good quality micrometer and check yours. You'll be glad you did. Now you can remark them and set them aside for the next time you run your valves.