My Bicycle Problem.

[Best Toy Ever]

I have had my Motorized Bicycle for four months. It is a 80cc 2 cycle engine. It was fine a month and then one night I had a massive wipe out on a gravel road. I would throttle up and the bike would go to full speed for a second then decelerate on it's own. Then, I bought a new carburetor and that didn't fix it. It just got worse, it would take at least 15 mins.
to start it. When purchased the spark plug, it cranked up immediately. Then the muffler cap came of and I rode it for a while without it. It would accelerate on it's own when it did. When I throttled all the way down, it would still accelerate. Actually, when I throttle up, the engine would die. It would slowly accelerate then decelerate, over and over again. Then
without any throttle from me continue to accelerate on it's own. Then, recently the bicycle will not even start. I bought a new spark plug a: NGK Spark Plug. After I installed this park plug, it will not even start. I don't think it is the spark plug anyway. In short, at the current moment, it takes forever to crank up, then sputters forward and cuts off. Side note
I have two motor head gaskets on it, one is new one is old. What is going on?

 

[bluegoatwoods]

Well......I'm not an expert. But your post gives me a bit to work with.

I'd start by inspecting your throttle cable from end to end. Your wreck might have given it a kink or gotten it hung up on something. I'd also make sure that the throttle slider is inserted correctly into the barrel. The accelerating and decelerating beyond your control thing seems hard to explain. But trouble with your cable or your slider seem like places to look.

You ought to also pull the spark plug, stick it back into the boot and lay the threads of the spark plug against your engine. Then spin your back wheel. If you get no spark, then you know that you've got trouble in the ignition system. If you get a nice, steady, strong spark, then you can look elsewhere.

With two head gaskets on that engine, you might be losing compression. Maybe the fit isn't tight or something like that.

You say that when you twist the throttle the engine bogs down? Maybe to the point of stalling? Then I'd also have a look at your choke. Maybe the lever has worked loose from the actual choke 'disk' and that disk is always covering your air intake.

 

[maniac57]

I'd also be looking hard at the throttle cable and carb. Crash damage can occur in the strangest places...
Look for small cracks causing air leaks as well.

 

[fatdaddy]

Also the key may have sheared on the magneto throwing it out of time. With the piston at TDC the magneto should look like this.
(KC gets the cred for the pic.)
fatdaddy.

 

[bairdco]

Check for an air leak in the manifold, carb, gasket area, etc. a small leak could cause a varying idle.

you probably won't find it if its really small, so it's best to redo the manifold gasket, carb to manifold fit, etc.

Could also be a tiny head gasket leak that seals when it heats up. pop the head off and check the gasket for blow by.

and like stated above, could just be a tweaked cable.

 

[fatdaddy]

I don't see any mention of the kill switch or the white wire. Disconnect the kill switch to eliminate the possibility of a defective one. And cut or cap off the white wire if you have one. Some newer engines don't come with the white wire. Make REAL sure no bare wires are touching anything. Take all coatings off the wire end that attaches to the coil, (black wire,) and also sand the coating off the coil where it touches the case. Then solder the black to black and the blue to blue. Don't worry about setting up the kill switch yet.Then get an auto grade plug wire and boot.
What I'm trying to do is eliminate the possibility of any shorts or bad connections. All it takes is one.
fatdaddy.


Well, It's been 5 days. Whats up with the bike bro?