HuaSheng 142F 49cc dies when I release gas throttle [solved]

[greenjon]

Today I got my project bike up and running. I'm using the HuaSheng 142F 49cc with a shift kit on a 7-speed.

It starts fine, grabs the clutch fine, and hauls me down the road fine. But when I release the throttle the engine dies. Is this somehow part of breaking the engine in, or is something wrong?

I started it with the choke closed; let it warm up a few minutes and then opened the air all the way.

I pedal started the bike in my lowest gear, then gave it some gas (not a lot, just enough to engage the clutch and give me some push). Then I released the gas a few seconds later and the engine died. I did this two or three times.

 

[greenjon]

I figured it out! The idle was set too low.
I hooked up a tachometer and saw it was only idling around 1300 RPM. I turned it up to 2000 and it works fine (doesn't die when I use and then release the throttle!)

 

[Beastiebikes]

How do you use a tachometer on these engines? Do you read the clutch bell?

 

[greenjon]

The tach I'm using is the cheap digital one from Amazon. It works by induction. There is a wire coming from the tach and one routes it to the spark plug wire. Then one wraps the tach wire around the spark plug wire ~5 times. Every time power flows to the spark plug, a magnetic field is created around the spark plug wire, and a small current is induced in the coil of wire around it that goes to the tach. Or something like that.

The tach can be set for two stroke or 4 stroke and possibly for multiple cyclinder engines.
It also tracks engine on time, which will be useful for changing the oil in 10 hours.

 

[Beastiebikes]

Very cool, but how does it track time. Like total run time? do you have to leave it on everytime you run it? Or is it timing?

 

[greenjon]

It tracks total run time including idling. It come on automatically when the spark plug starts firing and shuts off after awhile when the sparks have stopped. It appears to store the total run time even when the battery is out, but I'm not sure for how long (long enough to do a battery change at least).