50cc cut out issue when going full speed?

Question

The bike is a Sachs Speedforce 50cc

Right. Was coming home from my Mums, and I noticed this slightly odd sound, sounded like something was spinning up and then slowing down again, a sort of buzzing sound. And, then something "popped" (it sounded like it popped) and the bike cut out.

I pulled over nice and safe, and had scratch of the old head.

The bike started up again, but kept on cutting out whenever I let go of the throttle (when it revved low) and sounded like the bike was drowning or something, sounded a bit like when you put your finger over the exhaust pipe and then it cuts out.

So, tried to get it moving (my first thought was it was the drive belt snapped) but it moved fine, only it cut out when it revved to low.

So, I wasn't going to risk anything, and pushed it the rest of the way home (lucky, only about 5 mins walk away)

Then I begun my investigation -- the engine was still warm, so it shouldn't cut out when on low revs.

I checked on the drive belt, it was fine, no problems (from what I can see)

I checked the air filter, it was dirty, but I didn't have any air filter cleaning stuff, so I just replaced it and tried to start the bike and hey presto, it didn't cut out.

So, I took it out for a spin.

It didn't cut out, however it still makes this odd noise when its going full speed, suggesting to me, it will happen again.

Now, the first thing is, it must be the air filter. But, what with the noise? I know its very difficult, as you can't hear it, but I hope with my other details, somebody may have some idea.

thanks :)

Answer 1

If you're running your bike enough to need a new air filter, maybe you've got a clogged muffler, too.  Those get filled with all kinds of nasty crud.  Unbolt it and bonk it on the side a few times and see what comes falling out.

I'm guessing the pop is an extra-rich firing cycle once in a while, if the muffler is so clogged that the cylinder can't scavenge the way it should.

I wish you the best - when my Express muffler gets clogged, the solution is to bake it in a fire for an hour.  No joke!

Answer 2

It could indeed be a clogged up exhaust.  could also be a bit of muck blocking a jet in the carb (cant remember how you spell carb...hurhet...ter).  But that exhaust thing is most likely.