On Friday, June 7, 2019 at 2:15:33 PM UTC-4, Rod Speed wrote:
"trader_4" wrote in message
...
On Friday, June 7, 2019 at 12:42:46 AM UTC-4, Xeno wrote:
On 7/6/19 10:43 am, trader_4 wrote:
On Thursday, June 6, 2019 at 5:39:33 PM UTC-4, Clare Snyder wrote:
On Thu, 06 Jun 2019 17:08:54 -0400, wrote:

On Thu, 6 Jun 2019 12:45:27 -0700 (PDT), trader_4
wrote:


OK, so here we go again. Last Fall I had trouble with this Sears
two
cycle leaf blower, where it would not start. Finally figured out it
was a stuck piston ring. The ring broke when I tried to get it out,
so I cleaned up the groove with a tiny screwdriver, got all the
carbon
out, got a new ring, put it in. In floated freely. Put it back
together and it ran fine for awhile, then I had carb troubles. So,
I bought a new carb from China and it ran better than when it was
new. I put maybe 8 hours of use on it last Fall. Now it won't start
again, won't fire.

After exhausting all possibilities, I took it apart again and the
piston ring is stuck again. Sides of the piston have some black,
shellac like stuff on it too. Broke the ring again, but have it
all cleaned up again. The question is why did it foul again?
Some more history, when this was new ten years ago, I should have
taken it back, because it didn't run well with no choke. So most
of the time on it, I ran it with half choke. Of course if they
had screws you could adjust, I could have tuned it, but instead I
just put up with it. So, first time the ring got stuck, I figured
it was probably from running it too rich all those years. After
putting
the new ring in, I probably ran it for a few hours with the old carb
and half choke. But after that I put the new carb on and it ran
beautifully, no choke. I made sure to use a modern synthetic oil,
mixed to the correct ratio. So, how did it get fouled again in just
8 hours? I know I should just put it out into the dump, but it's
otherwise in fine shape and runs great when it runs and this has
become
kind of a battle of wills.


Just a wild-ass guess - maybe the original stuck ring
caused some deformation/wear in the cylinder wall
that caused the new ring to stick ?
John T.
Not likely. Are you mixing the synthetic oil to the engine spec or
the oil spec?

It was to the engine spec, or close to it. 40:1 I have that and a
lawn edger, one might be 40, the other 45, I know if one is different,
I just split the difference. I can check tomorrow and see what the oil
says.




Are you using ethanol free gas?

No, I don't even know where to find it around here. I guess I could
buy the super expensive stuff at HD, but then if it's ethanol related,
why did it work for 10+ years, but now foul the ring, then foul it
again in only 8 hours? Also, in the fall, when I was having trouble,
I did mix up fresh gas and used it within a month or two. So it's not
like it had old gas that then ran through it causing the problems.
It was fresh gas that caused the trouble. I think I recall it getting
harder to start the last couple times in Dec, then would not start at
all just now.

But in general, usually, the gas does sit around. You know how it
goes.
I have a one gallon
plastic jug, the little oil things come in a size that makes a gallon.
But after the fall, whatever is left, sits there. I guess I could
throw
it out. But funny thing here, I took the carb apart and it was
spotless, no sign of anything fouling.



I'd throw in a new ring,
mix ethanol free gas with the synthetic oil (not marine, right?)

No, it's regular synthetic, not marine.


to
the oil manufacturer's sprc - i.e. 50:1 even if the engine says 16:1 -
and add some "sea foam" to the mix according to the instructions on
the can.
If you are using marine or water-cooled snowmobile oil that could be
your problem - weedeaters run a lot hotter than water cooled marine
engines. The cyl walls won't cause the ring to stick in the piston.

Thanks.

In the US, the fuel is, for want of a better word, crap. You cannot
*leave it* in the machine and you need to properly *winterise* any and
all petrol powered equipment. EG.

https://www.briggsandstratton.com/na...-properly.html

The shellac like appearance is from the breakdown of the fuel that is
remaining in the cylinders. It is normal to run the devices out of fuel
but with two stroke engines that's a fraught practice. In that case you
need to use a *fuel stabilizer*.

That's an interesting theory, that the shellac like stuff isn't from
combustion of the fuel, but from whatever is left that later dries
up and hardens. But it doesn't really explain how a new ring
failed in so few hours, while the previous one lasted ten years,
with no change in how I've used it.

Maybe the second one was just a dud ring.

What is a dud ring? It's just spring steel. The problem isn't the
ring, it's that carbon and gunk fills up the groove so the ring sticks,
it binds up in the piston groove.