On Thu, 12 May 2011 19:29:43 -0500, jim
wrote:

wrote:

On Thu, 12 May 2011 13:15:28 -0500, jim
wrote:

wrote:

On May 7, 5:50 pm, Joseph Gwinn wrote:
I have a lawnmower and a snowblower, both from Honda, and both are hard
to start at the beginning of their season. The lawnmower is the worst
offender, by far, so I'll focus on it.

I would always get the mower going, but it could take all day the first
time. After that initial difficult start, starting was reasonably easy
for the rest of the season.

I have heard various theories on why this is so:

1. Gas varnished up over the winter. I took the carb apart - clean as
a whistle. Nor did gas stabilizer make any difference.

2. Water (from condensation) in the gas. Hmm, hard to do with the 10%
alcohol in all gas available these days.

3. Volatiles evaporating from the gas in the tank over the winter.
Also, various stories saying that winter gas and summer gas are
different, the difference being how volatile the gas is, with winter
needing more volatile gas than summer. Hmm, this could be at least part
of an answer.

So, this year, when I first tried to start the lawnmower for the summer,
had the usual problems. Tried the usual dodges, like leaving the mower
out in the sun to warm up, and putting fresh gas in the tank, but no go.

Volatiles? Ether! So, I gave it a squirt of starting fluid.

Started right up on the first try, and subsequent starts were of normal
difficulty, probably because all the old gas was by then flushed out of
the carb.

So, theory 3 seems to be correct.

And a dash of Naptha in the gas may do the same.

Joe Gwinn

Ran the gas out of mine completely last fall, got some fresh 91 octane
last week, filled the tank, it fired off in three pulls, needed
another pull to keep going. Has a gravity feed tank. I've found 91
octane is needed with the alcohol contaminated gas for it to chop
through the heavier weeds, otherwise it stalls. Difference in
performance is quite noticiable. Briggs engine, about 25 years old.
In the past, if I left gas in it, even if the float bowl was left dry
I'd have to disassemble and hit all the parts with carb cleaner, then
it would run. I also think the alcohol is the reason they're sticking
6 hp engines on the same mowers they used to put 3.5 hp engines. That
and CA smog specs. Either that or the horses have shrunk down.

The horses have shrunk down. I think what they were calling a 5 hp was
practically identical to what they sold as 3.5 hp for 50 years. There
was a Nationwide class action lawsuit against B&S. As a consequence they
no longer use hp ratings. They are rated by torque.

-jim



Stan
The REASON they now sell by torque is the HP rating was at 3600 RPM,
and with the safely regulations today most lawn mowers are running
their engines BELOW that speed - many only 2400 RPM
A 6 hp motor at 3600 rpm is 8.75 ft lbs of torque. At 2400 RPM that's
only something like 4 HP.

Briggs was perfectly happy with using horsepower to rate their engines
until they lost 51 million dollars in lawsuits because of proven false
claims regarding horsepower rating. The courts ordered Briggs (and other
small engine companies) to use the SAE standards for torque or
horsepower as determined by an independent test facility for any claims
they make. Previously the companies were just making up power ratings as
they saw fit.

After the court order Briggs quit giving horsepower ratings entirely
rather than put the much lower hp rating back on the same engines as the
court order would have required.

Briggs took what for 50 years they called a 3.5 horsepower and simply
lied and labeled it as a 5 or 6 horsepower. Then when they got caught
they didn't want their fraud to be widely known so they came up with a
story that horsepower is a lousy way to rate engines and torque is a
much better way to rate small engines.
From what I've read / heard, you are blowing more smoke than a 15
year old Briggs.
Yes, the manufacturers were sued - but they were not NECESSARILY
deceptive in their ratings. The engines WERE rated at a given stated
RPM - and if run at that RPM with the torque ratings currently on the
engines they WOULD produce (in most cases) the advertized horsepower.

If you take the torque available at whatever RPM the engine is run at
and multiply the two, then devide by 5252, you get the horsepower.

Look at the Torque rating of any engine out there today, and multiply
it by 3600, then devide by 5252, and you will find the result is
extremely close to the HP the engine was formerly advertized/sold
with.

The ONLY engine description that cannot be argued is DISPLACEMENT -
which is more and more becoming the standard way to advertize small
engines. This rating still does not tell you a whole lot, because the
power differs greatly depending on the engine design. Your weed eater,
leaf blower, chain-saw etc will have a 30cc, 35cc, or 40cc etc
engine., which may be producing , say 5HP from 40cc at 6000 RPM. (4 ft
lbs of torque at 6000 RPM - being a 2 stroke engine) Your lawnmower
may have a 135 cc or 8.24 cubic inches 4 stroke- roughly 3.5HP at 3600
RPM.. A 5HP L-Head Briggs was 12.5 cubic inches, or 204 cc. The same
displacement OHV Intek engine is a 6.5HP engine at the same 3600 RPM
due to higher volumetric efficiency and higher compression ratio. This
translates to about 9.5 ft lbs torque at 3600 RPM - and the engine
LIKELY produces a peak torque of about11 ft lb at 2400 RPM (5 HP),
while the L- Head 5HP engine likely produced a peak HP of about 9.5ft
lb at 2400, for a HP of about 4.25, and 7.2 ft lbs at 3600, for the
5HP rating.

The torque drops off with speed due to poor breathing (volumetric
efficiency) - the carting guys tune the intakes and exhausts to
improve the efficiency, which increases the torque at higher speeds -
producing more HP.