Briggs/Stratton 4 hp Quatro


P

Puddin' Man

Briggs/Stratton 4 hp Quatro

On an MTD 21 " mower, maybe 8 years old.

For several years, even right after disassembling/cleaning
air filter, carb, changing oil, etc etc, it'll start up
and run steady for about 10 seconds, then it revs up and
down (almost killing) in an endless cycle. About 30% of
similar B&S mowers I see running in the 'hood do the
same thing. Oh, and, of course, it fouls spark plugs.

I cleaned it up last fall. Start it up this spring, does
the same thing, but, after reaching minimum rpm, it
clanks while trying to rev up again. Sounds like serious
pre-ignition or even a flogging rod knocking. Motor has
had no hard use: I mow my little lawn at an idle.

Anybody got a handle on such behavior? Smokes a little
only when first started. Compression feels OK.

Cheers,
Puddin'

"Life is nothing but a competition to be the criminal rather
than the victim."
- Bertrand Russell
 
P

Puddin' Man

Your "FAM" is the flywheel.
I kinda figgered ...
It's weighted & balanced, & contains
magnets for the magneto ignition, as well as fins to move air over the
engine for cooling.
Approximate weight of blade assy? Approximate weight of FAM?
Maybe it's "half a flywheel"? :)
It is keyed to the crankshaft.
OK ...
Evem if you get the nut off, you will still need a puller.
Thanks. I guess I'll start by pricing the Honda's.

Tecumseh's are no less a PITA?

P

"Life is nothing but a competition to be the criminal rather
than the victim."
- Bertrand Russell
 
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D

DanG

The Honda is prone to the exact same problems.

You either need to buy, own, and learn to use the tools to deal
with a lawn mower engine, or you hire someone else to do it for
you, or you buy a new lawnmower as necessary. Simple choices.

Honda engines are very well made and would be my engine of choice,
but they also need attention.
 
P

Puddin' Man

Well, I have not had a Briggs failure(of my own, anyway), & the only
thing I've had to repair on my Tecumseh's are the flywheel key(my fault)
and a head gasket. I can do both of these jobs in a few minutes
blindfolded.
Absolutely! :)
The Briggs failure was my cousin's 6.0. Ran it low on oil & threw a
rod(but not through the case).

I ordered a new piston, rod, & gaskets, & put it back together about 5
years ago with the advice to watch the oil, & use synthetic. It's still
running strong. Unfortunately, the oil never gets changed.

If you want to do these simple repairs, you need to have the right tools
& knowledge.
Is true, is true. Mea Culpa!

Only thing is, it hasn't run properly for years, and:

And there's no mixture adjust on the "carb", etc etc.

And when I post a query -here- as to why it fouls plugs, revs
up and down, etc, I get 100 zillion blank stares. :)

So, question becomes, how much do I wanna invest in tools, etc
to repair/maintain my B&S? Prevalent evidence indicates they
(say, 3.5-6 hp, enyway) were designed as throw-aways.

Thx,
Puddin'

"Life is nothing but a competition to be the criminal rather
than the victim."
- Bertrand Russell
 
P

Puddin' Man

The Honda is prone to the exact same problems.
Having had a Honda (not a mower) in the garage these
last 19 years:

"I Believe Every Word You Say!" :)

Puddin'

"Life is nothing but a competition to be the criminal rather
than the victim."
- Bertrand Russell
 
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Briggs/Stratton 4 hp Quatro

On an MTD 21 " mower, maybe 8 years old.

For several years, even right after disassembling/cleaning
air filter, carb, changing oil, etc etc, it'll start up
and run steady for about 10 seconds, then it revs up and
down (almost killing) in an endless cycle. About 30% of
similar B&S mowers I see running in the 'hood do the
same thing. Oh, and, of course, it fouls spark plugs.

I cleaned it up last fall. Start it up this spring, does
the same thing, but, after reaching minimum rpm, it
clanks while trying to rev up again. Sounds like serious
pre-ignition or even a flogging rod knocking. Motor has
had no hard use: I mow my little lawn at an idle.

Anybody got a handle on such behavior? Smokes a little
only when first started. Compression feels OK.

Cheers,
Puddin'

"Life is nothing but a competition to be the criminal rather
than the victim."
- Bertrand Russell
Found out that there is a plastic duct that connects from the carb to the engine, it was broken allowing air in and destroying the negative pressure needed to draw fuel. Engine was revving and dying every second and a half, never stopped and worked better under load for some reason.
 

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