>
> --- Fly Bum <fly_it_slow@yahoo.com> wrote:
> > Trying to help a friend get his recently purchased
> > 2nd
> > gen running.  He has a street ported 13b with a
> > weber
> > copy side draft carb.  The engine starts and runs
> > fine
> > for about 3 minutes and then it starts
> > backfiring/popping (a little) and loses power and
> > quits.  Let it sit for a while and it will start
> > back
> > up and run ok again for another 3 minutes.
> >
> > I don't think it's the fuel pump cutting out since
> > he
> > has it hardwired on and it seems to be putting out
> > plenty of flow.
> >
> > What else to look for?
> >
> > Thanks guys!
> >
> > Joa

Joa as several have mentioned, it is either too lean a fuel mixture or a
misfiring ignition set up.  Since you mention he is using a Weber
carburator, it sounds like to me the engine starts fine with the proper
mixture and then within three minutes starts to backfire - indicating too
lean a mixture or a misspark.  Howver, I would be willing to bet that the
Weber tank bowl is running dry/low  after 3 minutes.  If fuel pressure is
adequate then the needle valve in the tank may be stuck/sticking and not
allowing more fuel into the tank or more likely restricting the flow causing
the bowl to run dry as the engine uses fuel. Stop the engine with the pump
still on and the bowl slowly fills back up until the engine is ran again.

 Now someone will probably tell me a weber doesn't have a fuel bowl {:>).

Ed Anderson