I think some of them even have plastic crankcases these days. I heard
once that honda has used carbon fiber pistons in some racing engines.
Composites have come a long way.
Loose bolts just about anywhere are a problem for 2 strokes as they
have sealed crankcases and rely on that to transfer the fuel/oil from
the carb to the crankcase then into the combustion chanber. I had one
that the cylinder to crankcase bolts had loosened. In any case
problems vary and engines can deteriorate or die in one shot. Depends
on the problem. Fuel issues are common in these smaller engines
because people don't use stabilizer or continue to use gas that is too
old even if it had stabilizer in it. And the fuel gets contaminanted
easily because it is poured form container to container or left open
to absorb water.
There's really two schools of thought here. Buy something of moderate
quality and plan on occasionally fixing a minor problem because it's
the last one you will buy for 30 years. Or buy a low end 2 stroke or
an electric one and just throw it away when it develops problems. If
you cant' fix it yourself the second path is probably the recommended
way to go as taking anything to the shop these days will easily result
in a bill that is a sizable fraction of the original price. Unless
you're in the commercial end of the business, plan on using it for
many hours daily, and paying maintenance is factored into your use.
Then you want to buy top of the line quality.
re: "...taking anything to the shop these days will easily result in a
bill that is a sizable fraction of the original price."
Especially when I only paid $55 on Craigslist for the blower!
Either I'm fixing this thing or it's back to Craigslist for another
re: "It still sounds odd that there's no gasket between carb and
I just looked at the on-line parts list for the 340BV and there is
indeed a gasket on the backside of the carb.
Then there's a heat shield, then another gasket, then a carb spacer
then another gasket then a baffle assembly then another gasket and
*then* the engine itself.
When the screws that hold the plastic crankcase cover become loose, it
sucks in air when the piston is on the up-stroke. This will result in
a lean mixture and usually too lean to run (same symtoms as a dirty
carb or not getting gas). If you richen the mixture with full choke or
spray starting fluid in it , it may fire.
I mentioned tightening all screws in my last post.
I wanted to blow the maple-copters off of the driveway and onto the
lawn so I could mow them up, so I figured whatever air I could get out
at full choke was better than nothing.
I found that if I feathered the 3 position choke lever I could get a
lot more power by holding it between the "fully closed" and "partial"
detents. If I let it drop into the "partial" detent it would stall -
at least at the beginning.
After about 10 minutes of run time, I found I could actually run it at
the partial setting for a few minutes before it would begin to labor.
If I moved the lever back towards fully closed, it would pick up speed
and I'd go through cycle again.
I wonder if it's slowly cleaning itself out.
It's very unlikely that your sthil or echo has float bowls.
Practically all these small 2 strokes have membrane carbs. I do
nothing special at the end of the year to any of my 2 strokes with
membrane carbs but I do always put gas stabilizer in my 2 stroke gas
all year round. You never know when the last fill up for a while is
going to be on these engines.
The membrane carbs are a lot more resistant to problems with gas
sitting in them for longer periods because there is so little gas in
the carb and no traditional bowl vent to the atmosphere but it is
still possible. Particularly if the gas may be contaminated with
You must not have read my OP very carefully.
The problem started way before storing the unit for the winter. As I
said, after a few hours of use last fall, it would no longer start.
I did pour out the gas and pull the cord a few times, but since it
wouldn't start, there was no way to know if the carb ran itself dry or
In fact, as per my OP, it actually starts now - which is an
improvement over last fall - but it won't run without the choke full
I'm sure it's a carb problem in any event.
Your basic problem is the mixture of fuel to air ratio. There are many
things that cause this condition. To fix the problem you must do all
of the following:
Make sure all screws are tight that hold the carb, crank, and any
other screw that may allow air into the cylinder.
Make sure the gas tank vent is working properly.
Replace the fuel lines and make sure the fuel filter is attached. They
become brittle, they are cheap. Hint: when replacing the fuel lines,
cut at an angle. This will allow it to pass thru the holes much
easier. Buy the correct size.
Replace the plug. I know you said it was new, but trust me on this.
Plugs can become useless if too much gas gets on them, therefore not
allowing the full electric charge to produce the spark required. Also,
even new plugs can be bad.
After doing ALL the above, you can try to start it. If you have the
same problem, you must dis-assemble the carb and blow out all the
passages. There are only a few parts. Take pictures at each step if
you don't feel confident. Reassemble. Take plug out and check for
spark to make sure you didn't "gas foul" the one you just put in.
That should do it.
On Wed, 19 May 2010 08:55:39 -0700, Hustlin' Hank wrote:
Yes, pictures are useful... on the small carbs I've seen, some of the
parts can fit in more than one location/orientation, so it can be useful
to take pictures (or, if you don't like getting your camera dirty, do
what I do and scribble down notes and diagrams on a scrap of paper. And
try not to lose the paper ;)
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