On Wed, 28 Mar 2012 09:19:19 -0700 (PDT), harry
wrote:

On Mar 27, 1:45Â*am, "Steve B" wrote:
I have a 21cc hedge trimmer. Â*A Craftsman. Â*It hasn't run for a while, but
the guy swore it was running when put up.

I put new gas in it, and checked the obvious. Â*It needed a new on/off
switch. Â*It has spark. Â*I can't get it to pop, even with shooting a little
gas into the carb, or on the sponge air cleaner.

When I pull the start rope, there isn't very much "POP" at all. Â*I mean
resistance that would come from good compression, or from firing and
igniting the gas/air mixture.

Just how much "POP" should be present, even if you have the switch off, and
aren't trying to start it, but just basically see how much compression it
has? Â*I call "POP" that instantaneous resistance on the pull rope where it
would hit TDC, or fire with a spark. Â*Does two strokes not have the "POP"
that four strokes have because of their different configuration?

Tomorrow, I'll pull the carb and see if there's anything obvious there. Â*The
primer bulb worked, no leakage, and filled up, presumably feeding gas to the
carb.

Steve

The thing you thinkis a carb may not be. A lot of these micro-motors
have minature petrol injection. It works by means of a diaphragm
pwered by crank case compression.
The advantage is, it works any way up.
The diaphragm can split. the two tiny check valves can leak.
Those are still carbs - not injectors. They are "regulator carbs"
with a diaphragm instead of a float, and a pulse powered fuel pump
(which has another diaphragm)

The thing you thinkis a carb may not be. A lot of these micro-motors
have minature petrol injection. It works by means of a diaphragm
pwered by crank case compression.
The advantage is, it works any way up.
The diaphragm can split. the two tiny check valves can leak.
Those are still carbs - not injectors. They are "regulator carbs"
with a diaphragm instead of a float, and a pulse powered fuel pump
(which has another diaphragm)

I have a vintage Honda FourTrax, the first year they were made. It wasn't
ridden much, then restored by Grandpa for his kid at a cost of $900. Tires,
and "stuff". Kid got busted for drugs, so Grandpa sold FourTrax. I picked
it up.

That early model has an electric fuel pump, as the carb is higher than the
gas tank. It is a damn nightmare. I finally went to a friend who works on
them, and asked what to do, as it was always acting up.

He sold me a Mikuni pulse operated fuel pump. All you need is a vacant
vacuum port on the carb, and the pulsation works a small diaphragm.
Marvelous concept, except for the small detail of no port on that Honda.

So, anyway, I got the electric one working. Hope it doesn't act up out in
the bush.

Sold the Mikuni to a friend who has a race bike, and he installed it on his,
and it fixed his fuel starvation caused fluttering.

The thing is elegantly simple. Three little nipples... vacuum, gas in, gas
out. Bolt it on anywhere.

Steve

On Apr 2, 5:49*pm, "Steve B" wrote:


I have a vintage Honda FourTrax, the first year they were made. *It wasn't
ridden much, then restored by Grandpa for his kid at a cost of $900. *Tires,
and "stuff". *Kid got busted for drugs, so Grandpa sold FourTrax. *I picked
it up.

That early model has an electric fuel pump, as the carb is higher than the
gas tank. *It is a damn nightmare. *I finally went to a friend who works on
them, and asked what to do, as it was always acting up.

He sold me a Mikuni pulse operated fuel pump. *All you need is a vacant
vacuum port on the carb, and the pulsation works a small diaphragm.
Marvelous concept, except for the small detail of no port on that Honda.

So, anyway, I got the electric one working. *Hope it doesn't act up out in
the bush.

Sold the Mikuni to a friend who has a race bike, and he installed it on his,
and it fixed his fuel starvation caused fluttering.

The thing is elegantly simple. *Three little nipples... vacuum, gas in, gas
out. *Bolt it on anywhere.

Steve

Those type fuel pumps are very common on many models of ATV's, Riding
mowers and others.

Hank