Posted by Nad R on May 13, 2011, 8:05 pm
> wrote:
>
>> I have an old Craftsman 6HP vertical shaft chipper/shredder that is giving me
>> trouble. The engine idles great, but at any higher speed, runs really rich,
>> making black smoke, and even spitting gas out the carb if I take the air
cleaner
>> off. It does not rev properly in the process, except when it first starts or
as
>> it runs out of gas.
>>
>> The diaphram in the carb looks excellent. It looks new. I might have replaced
it
>> a couple years ago when I acquired this unit used. The gas valve it operates
>> seems to operate also. If I blow into the fuel inlet, no air passes until I
push
>> up on the needle that opens the fuel flow. I even tried installing a layer of
>> plastic from a bag "outside" of the diaphram (between it and the cover) to
>> eliminate the possibility of any leaks through the diaphram, with no effect.
>>
>> Would a bad diaphram allow the idle to work great, while higher speeds are
all
>> super rich?
>>
>> The idle needle adjustment works properly. The high speed needle adjustment
>> seems to have no effect, other than if I remove it completely, at which point
>> the engine will quickly speed up like it should work for a few seconds before
it
>> then dies.
>>
>> Any ideas? Is there something I haven't thought of that could be repaired on
>> this carb/engine?
>>
>
> I would examine the muffler for a clog. Does this mower have a spark
> arrester? Clean that also.
>
> ...then maybe valve seats
I sometimes wonder about old engines and E10 gas. Gas companies no longer
tell anyone that almost all regular gas in the US contains ethanol. I see
these little bottles of E10 fuel additives in stores now for small engines.
I wonder if any how much damage is being done to old small engines.
--
Enjoy Life... Nad R (Garden in zone 5a Michigan)
Posted by hr(bob) hofmann@att.net on May 13, 2011, 8:54 pm
> I have an old Craftsman 6HP vertical shaft chipper/shredder that is giving me
> trouble. The engine idles great, but at any higher speed, runs really rich,
> making black smoke, and even spitting gas out the carb if I take the air cleaner
> off. It does not rev properly in the process, except when it first starts or as
> it runs out of gas.
> The diaphram in the carb looks excellent. It looks new. I might have replaced it
> a couple years ago when I acquired this unit used. The gas valve it operates
> seems to operate also. If I blow into the fuel inlet, no air passes until I push
> up on the needle that opens the fuel flow. I even tried installing a layer of
> plastic from a bag "outside" of the diaphram (between it and the cover) to
> eliminate the possibility of any leaks through the diaphram, with no effect.
> Would a bad diaphram allow the idle to work great, while higher speeds are all
> super rich?
> The idle needle adjustment works properly. The high speed needle adjustment
> seems to have no effect, other than if I remove it completely, at which point
> the engine will quickly speed up like it should work for a few seconds before it
> then dies.
> Any ideas? Is there something I haven't thought of that could be repaired on
> this carb/engine?
It seems fairly obvious that fuel is bypassing the high-speed jet.
Maybe the needle has worn down. If gas was not bypassing the high-
speed jet, with the jet fully screwed in, the engine would die at high
speeds, not run rich and belch black smoke. I would look at the
highspeed jet needle and its valve seat and see if either are worn.
Posted by jw on May 14, 2011, 2:45 pm
wrote:
>hr(bob) hofmann@att.net wrote:
>>> I have an old Craftsman 6HP vertical shaft chipper/shredder that is
>>> giving me trouble. The engine idles great, but at any higher speed,
>>> runs really rich, making black smoke, and even spitting gas out the
>>> carb if I take the air cleaner off. It does not rev properly in the
>>> process, except when it first starts or as it runs out of gas.
>>>
>>> The diaphram in the carb looks excellent. It looks new. I might have
>>> replaced it a couple years ago when I acquired this unit used. The
>>> gas valve it operates seems to operate also. If I blow into the fuel
>>> inlet, no air passes until I push up on the needle that opens the
>>> fuel flow. I even tried installing a layer of plastic from a bag
>>> "outside" of the diaphram (between it and the cover) to eliminate
>>> the possibility of any leaks through the diaphram, with no effect.
>>>
>>> Would a bad diaphram allow the idle to work great, while higher
>>> speeds are all super rich?
>>>
>>> The idle needle adjustment works properly. The high speed needle
>>> adjustment seems to have no effect, other than if I remove it
>>> completely, at which point the engine will quickly speed up like it
>>> should work for a few seconds before it then dies.
>>>
>>> Any ideas? Is there something I haven't thought of that could be
>>> repaired on this carb/engine?
>>
>> It seems fairly obvious that fuel is bypassing the high-speed jet.
>> Maybe the needle has worn down. If gas was not bypassing the high-
>> speed jet, with the jet fully screwed in, the engine would die at high
>> speeds, not run rich and belch black smoke. I would look at the
>> highspeed jet needle and its valve seat and see if either are worn.
>Excellent ideas. Thanks for your help.
While you're at it, get a complete carb kit and rebuild the whole
thing. No sense tearing it apart piece by piece, and possibly having
leaky gaskets that were reused. If it has a float, that may be
sticking. Rip it apart, thoroughly soak the casting in a solvent, and
make sure all the passages are clean (use an air compressor). Then
put back together with all new gaskets and seals.
Posted by ransley on May 14, 2011, 11:32 am
> I have an old Craftsman 6HP vertical shaft chipper/shredder that is giving me
> trouble. The engine idles great, but at any higher speed, runs really rich,
> making black smoke, and even spitting gas out the carb if I take the air cleaner
> off. It does not rev properly in the process, except when it first starts or as
> it runs out of gas.
> The diaphram in the carb looks excellent. It looks new. I might have replaced it
> a couple years ago when I acquired this unit used. The gas valve it operates
> seems to operate also. If I blow into the fuel inlet, no air passes until I push
> up on the needle that opens the fuel flow. I even tried installing a layer of
> plastic from a bag "outside" of the diaphram (between it and the cover) to
> eliminate the possibility of any leaks through the diaphram, with no effect.
> Would a bad diaphram allow the idle to work great, while higher speeds are all
> super rich?
> The idle needle adjustment works properly. The high speed needle adjustment
> seems to have no effect, other than if I remove it completely, at which point
> the engine will quickly speed up like it should work for a few seconds before it
> then dies.
> Any ideas? Is there something I haven't thought of that could be repaired on
> this carb/engine?
The float could be stuck open. But If so you would have gas in the
oil. If you do, gas in oil can thin it and ruin the motor. but gas
pouring out the carb is likely the float. Does choke stay open, I
would not run it till you go over everything and change the oil. How
is you oil level now, if its up its the float.
Posted by zxcvbob on May 16, 2011, 9:43 am
ransley wrote:
>> I have an old Craftsman 6HP vertical shaft chipper/shredder that is giving me
>> trouble. The engine idles great, but at any higher speed, runs really rich,
>> making black smoke, and even spitting gas out the carb if I take the air
cleaner
>> off. It does not rev properly in the process, except when it first starts or
as
>> it runs out of gas.
>>
>> The diaphram in the carb looks excellent. It looks new. I might have replaced
it
>> a couple years ago when I acquired this unit used. The gas valve it operates
>> seems to operate also. If I blow into the fuel inlet, no air passes until I
push
>> up on the needle that opens the fuel flow. I even tried installing a layer of
>> plastic from a bag "outside" of the diaphram (between it and the cover) to
>> eliminate the possibility of any leaks through the diaphram, with no effect.
>>
>> Would a bad diaphram allow the idle to work great, while higher speeds are all
>> super rich?
>>
>> The idle needle adjustment works properly. The high speed needle adjustment
>> seems to have no effect, other than if I remove it completely, at which point
>> the engine will quickly speed up like it should work for a few seconds before
it
>> then dies.
>>
>> Any ideas? Is there something I haven't thought of that could be repaired on
>> this carb/engine?
>
> The float could be stuck open. But If so you would have gas in the
> oil. If you do, gas in oil can thin it and ruin the motor. but gas
> pouring out the carb is likely the float. Does choke stay open, I
> would not run it till you go over everything and change the oil. How
> is you oil level now, if its up its the float.
That would be a Tecumseh engine, not a B&S.
-Bob
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>
>> I have an old Craftsman 6HP vertical shaft chipper/shredder that is giving me
>> trouble. The engine idles great, but at any higher speed, runs really rich,
>> making black smoke, and even spitting gas out the carb if I take the air