My bike stalls out in an odd way...

[jdmphotography]

Hi all,

This is my first post to this forum, but have been using it for months. It is an amazing resource, and this is the first time I haven't found a thread that answers my question. (I have an 80cc 2-stroke on a cruiser frame btw)

My issue:

When I first start up the bike it does a very strange thing as it warms up: I prime it, pedal, pop the clutch, flip the choke down, and it roars to life... but then in slowly loses thunder and stalls out.

I go through the process again and it does the same thing, but tries to hang on. As it dies it will gain a bunch of power suddenly (almost throwing me sometimes) and then die back down, pick back up, die back down, die.

Most of the time on the third attempt, i can push through it, and the issue stops till next time it cools down. (although I do sometimes hear a fluctuation in the sound of the motor, with a similar pacing to the stalling)

My friends and I have built 4 of these bikes in different configurations. Mine is the only one with the stock exhaust, and the only one that has this issue. Is my engine having trouble "breathing"? Do I need to mod my tail pipe? (and if so how? can I just drill a couple of holes in it?)

[Large Filipino]

Sounds like an air leak to me. When it starts to die and you flip the choke does it pick up again? Check for leaks around your intake tube on both ends. You may also need to O ring your carb there's a thread about this somewhere.

[orbit222]

Air leak sounds like a good guess... spray some carb cleaner on all the seams while she's running and you'll get your answer. Another place to look is at your hub. Sometimes the sprocket will rub on the dust cover of a coaster hub just enough to ruin performance- does she ride well with the peddles?

[Bikeguy Joe]

It works fine after awhile? Hmmm. very slight air leak? Leave the choke on a little while longer, and see what happens.

Also, when is the last time you changed the plug?
What mix are you running?

[jdmphotography]

I am just at the tail end of a 50 mile break in. I am at 16:1 about to switch over to 20:1.

Also I have never changed the plug.

When I leave the choke on a little longer most the time it just starts to putter out, but the longer I can wait, the more power when it roars up.

[jdmphotography]

and she peddles great- I bored out the rear sprocket and bent the coaster arm, so no rubbing.