Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.

On 09/19/2020 01:14 PM, wrote:
Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.


Any other fuel obstructions? Can the tank breathe?

On Sat, 19 Sep 2020 15:14:35 -0400, wrote:

Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.
Sounds like it is running lean - likely a jet plugging up?
What gasoline are you using?
Try opening the mixture screw 1/4 turn - I think a 1991 still has
adjustable jets?
If not (or even if -- - ) buy some SeaFoam fuel conditioner and give
it a good dose in the tank.

Running ethanol fuel (even E10) can also lean it out enough to make it
surge - I always use premium Shell or premion Canadian Tire or Costco
fuel (no ethanol) in my small engines.(here in Waterloo Ontario - so
it will be the same for you out in your neck of the woods)

On Sat, 19 Sep 2020 23:07:26 -0400, Clare Snyder
wrote:

On Sat, 19 Sep 2020 15:14:35 -0400, wrote:

Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.
Sounds like it is running lean - likely a jet plugging up?
What gasoline are you using?
Try opening the mixture screw 1/4 turn - I think a 1991 still has
adjustable jets?
If not (or even if -- - ) buy some SeaFoam fuel conditioner and give
it a good dose in the tank.

Running ethanol fuel (even E10) can also lean it out enough to make it
surge - I always use premium Shell or premion Canadian Tire or Costco
fuel (no ethanol) in my small engines.(here in Waterloo Ontario - so
it will be the same for you out in your neck of the woods)


Thanks Clare - I'll give the Seafoam a try & premium gas.
I've just been using regular gas and adding some stabilizer
up-to-now.
It's overdue for the annual oil change also - so I'll replace the
air filter as well ... perhaps I'm just paying-the-price of
neglecting that bit of maintenance ...
John T.

wrote:
Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.

Like another post said, a jet is probably plugged up.

Mine was having problems, until I took a tip cleaner for a cutting torch, the kind that have tiny drill bits, and drilled out the jets. The bit I used to finally get it unclogged at first seemed a little big, but now it runs like a new one, and it's 22 years old.

Most welding shops have one, and ebay has them.

It runs so smooth......

On Tuesday, September 22, 2020 at 1:16:13 AM UTC-4, mysterious traveler wrote:
wrote:
Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.

Like another post said, a jet is probably plugged up.

Mine was having problems, until I took a tip cleaner for a cutting torch, the kind that have tiny drill bits, and drilled out the jets. The bit I used to finally get it unclogged at first seemed a little big, but now it runs like a new one, and it's 22 years old.

Most welding shops have one, and ebay has them.

It runs so smooth......

Agree, first suspect in anything like this is a fouled carb. I would identify
it and get a rebuild kit, they are available on Ebay for common carbs for
under $10 bucks. The kit includes new seals, needle valve, welch plugs, etc.
Take it apart, take pictures if needed as you do it. Clean it out with carb
cleaner or brake cleaner, blow it out. Be careful blowing it out, make sure
there are no parts left that you will blow out and lose. There are Youtube
videos too. Whole aftermarket carbs are available on Ebya too, typically for
$25 or so for many common carbs. He can probably take it apart, clean it out,
reassemble without the rebuild kit, but it's better to have it.

One note, the rebuild kits typically don't include the gasket between carb
and intake. So check and if you need one of those order it separately.

On Tue, 22 Sep 2020 05:40:40 -0700 (PDT), trader_4
wrote:

On Tuesday, September 22, 2020 at 1:16:13 AM UTC-4, mysterious traveler wrote:
wrote:
Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.

Like another post said, a jet is probably plugged up.
Mine was having problems, until I took a tip cleaner for a cutting torch,
the kind that have tiny drill bits, and drilled out the jets.
The bit I used to finally get it unclogged at first seemed a little big,
but now it runs like a new one, and it's 22 years old.
Most welding shops have one, and ebay has them.
It runs so smooth......

Agree, first suspect in anything like this is a fouled carb. I would identify
it and get a rebuild kit, they are available on Ebay for common carbs for
under $10 bucks. The kit includes new seals, needle valve, welch plugs, etc.
Take it apart, take pictures if needed as you do it. Clean it out with carb
cleaner or brake cleaner, blow it out. Be careful blowing it out, make sure
there are no parts left that you will blow out and lose. There are Youtube
videos too. Whole aftermarket carbs are available on Ebya too, typically for
$25 or so for many common carbs. He can probably take it apart, clean it out,
reassemble without the rebuild kit, but it's better to have it.
One note, the rebuild kits typically don't include the gasket between carb
and intake. So check and if you need one of those order it separately.



Thanks for the input. I hope to look into it today.
I'll try a few preliminary & simple things before a carb re-build.

First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?
Also a good cleaning around the carb linkages.
I bought a can of SeaFoam yesterday to try in the gas tank.
John T.

On 09/22/2020 07:03 AM, wrote:
First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?

It's not gravity feed?

In article ,
says...

First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?



In simple terms there is a diaphram on the back of the pump. There is a
hole in the crankcase (not the actual cylinder where the piston is)
behind the fuel pump and as the piston goes up and down the air pressure
works the fuel pump diaphram.

On 9/20/2020 9:40 AM, wrote:
On Sat, 19 Sep 2020 23:07:26 -0400, Clare Snyder
wrote:

On Sat, 19 Sep 2020 15:14:35 -0400, wrote:

Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.
Sounds like it is running lean - likely a jet plugging up?
What gasoline are you using?
Try opening the mixture screw 1/4 turn - I think a 1991 still has
adjustable jets?
If not (or even if -- - ) buy some SeaFoam fuel conditioner and give
it a good dose in the tank.

Running ethanol fuel (even E10) can also lean it out enough to make it
surge - I always use premium Shell or premion Canadian Tire or Costco
fuel (no ethanol) in my small engines.(here in Waterloo Ontario - so
it will be the same for you out in your neck of the woods)


Thanks Clare - I'll give the Seafoam a try & premium gas.
I've just been using regular gas and adding some stabilizer
up-to-now.
It's overdue for the annual oil change also - so I'll replace the
air filter as well ... perhaps I'm just paying-the-price of
neglecting that bit of maintenance ...
John T.


I never ever run anything but non-ethanol gasoline in my yard
equipment - that is chainsaws , tractor , tiller , line trimmer and log
splitter . Same with my generator , nothing but pure non-eth gas . Since
Stihl calls for minimum 89 octane gas for their line trimmers and
chainsaws , I've been mixing 92 and 87 50/50 for those tools that use
oil mix fuel . The tractor , generator , tiller , and log splitter get
straight 87 . I am luckier than many , we have several stations that
sell non-eth gas in both flavors here . Around here alcohol is for
drinkin' , not burnin' .
--
Snag

On Tue, 22 Sep 2020 07:35:25 -0600, rbowman
wrote:

On 09/22/2020 07:03 AM, wrote:
First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?

It's not gravity feed?


No - there's a photo in this thread if you scroll down :

https://www.wheelhorseforum.com/topi...pump-question/

... which also has me thinking about the surging being
caused by a fuel pump problem.

John T.

On Tue, 22 Sep 2020 11:29:41 -0400, wrote:

On Tue, 22 Sep 2020 07:35:25 -0600, rbowman
wrote:

On 09/22/2020 07:03 AM, wrote:
First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?

It's not gravity feed?


No - there's a photo in this thread if you scroll down :

https://www.wheelhorseforum.com/topi...pump-question/

.. which also has me thinking about the surging being
caused by a fuel pump problem.

John T.

Sounds more like the governor. Make sure there are no binds in the
linkage.

On Tue, 22 Sep 2020 11:29:41 -0400, posted for all of us
to digest...


On Tue, 22 Sep 2020 07:35:25 -0600, rbowman
wrote:

On 09/22/2020 07:03 AM, wrote:
First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?

It's not gravity feed?


No - there's a photo in this thread if you scroll down :

https://www.wheelhorseforum.com/topi...pump-question/

.. which also has me thinking about the surging being
caused by a fuel pump problem.

John T.

Nice forum there. Wish others were like that...

--
Tekkie

On Tue, 22 Sep 2020 10:11:32 -0400, Ralph Mowery posted for all of us to
digest...


In article ,
says...

First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?



In simple terms there is a diaphram on the back of the pump. There is a
hole in the crankcase (not the actual cylinder where the piston is)
behind the fuel pump and as the piston goes up and down the air pressure
works the fuel pump diaphram.

Thanks for the explanation added to my mind.:-)

--
Tekkie

On Wed, 23 Sep 2020 15:59:00 -0400, Tekkie®
wrote:


On Tue, 22 Sep 2020 11:29:41 -0400, posted for all of us
to digest...


On Tue, 22 Sep 2020 07:35:25 -0600, rbowman
wrote:

On 09/22/2020 07:03 AM, wrote:
First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?

It's not gravity feed?


No - there's a photo in this thread if you scroll down :

https://www.wheelhorseforum.com/topi...pump-question/

.. which also has me thinking about the surging being
caused by a fuel pump problem.

John T.

Nice forum there. Wish others were like that...


Yep - I just re-discovered it .
Downloaded the Manual for my Onan P220 engine !
There was also a good Yahoo-Group for WheelHorse
but I haven't looked there in years.
John T.

On Tue, 22 Sep 2020 09:03:41 -0400, wrote:

On Tue, 22 Sep 2020 05:40:40 -0700 (PDT), trader_4
wrote:

On Tuesday, September 22, 2020 at 1:16:13 AM UTC-4, mysterious traveler wrote:
wrote:
Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.

Like another post said, a jet is probably plugged up.
Mine was having problems, until I took a tip cleaner for a cutting torch,
the kind that have tiny drill bits, and drilled out the jets.
The bit I used to finally get it unclogged at first seemed a little big,
but now it runs like a new one, and it's 22 years old.
Most welding shops have one, and ebay has them.
It runs so smooth......

Agree, first suspect in anything like this is a fouled carb. I would identify
it and get a rebuild kit, they are available on Ebay for common carbs for
under $10 bucks. The kit includes new seals, needle valve, welch plugs, etc.
Take it apart, take pictures if needed as you do it. Clean it out with carb
cleaner or brake cleaner, blow it out. Be careful blowing it out, make sure
there are no parts left that you will blow out and lose. There are Youtube
videos too. Whole aftermarket carbs are available on Ebya too, typically for
$25 or so for many common carbs. He can probably take it apart, clean it out,
reassemble without the rebuild kit, but it's better to have it.
One note, the rebuild kits typically don't include the gasket between carb
and intake. So check and if you need one of those order it separately.



Thanks for the input. I hope to look into it today.
I'll try a few preliminary & simple things before a carb re-build.

First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?
Also a good cleaning around the carb linkages.
I bought a can of SeaFoam yesterday to try in the gas tank.
John T.



Finally got a-round-tuit today.
Dumped some Seafoam in the tank and gave it a good shake-up.
Started the motor & gave it a few minutes of running - revving it up
several times. This was just to get the Seafoam into the carb.
Let it sit for a few hours while I trimmed with the little push mower.
Started it up again - not much difference - so I revved it out
some more and shut it down.
Removed fuel hose from tank outlet and forced some air
back-flushed back through the valve into the tank
using a big plastic syringe. Flushed the fuel hose from fuel pump
to tank outlet ; partly removed the fuel pump & cleaned crud
from around the outside / backside ; tapped & wiggled the fuel pump
to clear any debris ; removed air filter housing - I should have
taken a photo of the years of crud build-up around the carb !
Clean shop-cloth into the carb top to keep it clean.
Used the shop vac & old toothbrush to clean it up ; a drop of oil
on the carb throttle linkage - considered pulling the top off the
carb - decided to see what these preliminary efforts would do -
- put it back together & it wouldn't fire ! AAgggh !
Took a sanity break & looked for the simple things - noticed the
coil plug-wire that I removed wasn't fully seated - duh.
It fired up and ran like a champ - mowed the lawn on even revs -
... at fairly low RPM which was not possible before.
I'm still pretty happy with my 1990 lawn tractor.
It will still need some re-build work - for the next 30 years -
: carb-job
: all new rubber lines fuel ; vacuum ; hydraulic ;
Rock solid engine & tranny - if I am any judge.
... I think I'll keep her ..
John T.

wrote in message
Finally got a-round-tuit today.
Dumped some Seafoam in the tank and gave it a good
shake-up.
Started the motor & gave it a few minutes of running -
revving it up
several times. This was just to get the Seafoam into the
carb.
Let it sit for a few hours while I trimmed with the little
push mower.
Started it up again - not much difference - so I
revved it out
some more and shut it down.
Removed fuel hose from tank outlet and forced some air
back-flushed back through the valve into the tank
using a big plastic syringe. Flushed the fuel hose from
fuel pump
to tank outlet ; partly removed the fuel pump & cleaned
crud
from around the outside / backside ; tapped & wiggled
the fuel pump
to clear any debris ; removed air filter housing - I
should have
taken a photo of the years of crud build-up around the
carb !
Clean shop-cloth into the carb top to keep it clean.
Used the shop vac & old toothbrush to clean it up ; a
drop of oil
on the carb throttle linkage - considered pulling the
top off the
carb - decided to see what these preliminary efforts
would do -
- put it back together & it wouldn't fire ! AAgggh !
Took a sanity break & looked for the simple things -
noticed the
coil plug-wire that I removed wasn't fully seated -
duh.
It fired up and ran like a champ - mowed the lawn on
even revs -
... at fairly low RPM which was not possible before.
I'm still pretty happy with my 1990 lawn tractor.
It will still need some re-build work - for the next
30 years -
: carb-job
: all new rubber lines fuel ; vacuum ; hydraulic ;
Rock solid engine & tranny - if I am any judge.
... I think I'll keep her ..
John T.


You figured it out ! Feels good eih? phil

On Fri, 25 Sep 2020 20:03:16 -0400, posted for all of us
to digest...


On Tue, 22 Sep 2020 09:03:41 -0400, wrote:

On Tue, 22 Sep 2020 05:40:40 -0700 (PDT), trader_4
wrote:

On Tuesday, September 22, 2020 at 1:16:13 AM UTC-4, mysterious traveler wrote:
wrote:
Looking for suggestions -
1991 Wheelhorse 520H hydro - the normally smooth running
20 hp Onan has started to hunt during operation
engine speed going up & down in steady waves
I installed a new fuel filter this morning - no change.
Any useful advice is appreciated.
John T.

Like another post said, a jet is probably plugged up.
Mine was having problems, until I took a tip cleaner for a cutting torch,
the kind that have tiny drill bits, and drilled out the jets.
The bit I used to finally get it unclogged at first seemed a little big,
but now it runs like a new one, and it's 22 years old.
Most welding shops have one, and ebay has them.
It runs so smooth......

Agree, first suspect in anything like this is a fouled carb. I would identify
it and get a rebuild kit, they are available on Ebay for common carbs for
under $10 bucks. The kit includes new seals, needle valve, welch plugs, etc.
Take it apart, take pictures if needed as you do it. Clean it out with carb
cleaner or brake cleaner, blow it out. Be careful blowing it out, make sure
there are no parts left that you will blow out and lose. There are Youtube
videos too. Whole aftermarket carbs are available on Ebya too, typically for
$25 or so for many common carbs. He can probably take it apart, clean it out,
reassemble without the rebuild kit, but it's better to have it.
One note, the rebuild kits typically don't include the gasket between carb
and intake. So check and if you need one of those order it separately.



Thanks for the input. I hope to look into it today.
I'll try a few preliminary & simple things before a carb re-build.

First thing will be figuring-out the fuel pump - it has a fuel hose
going in a fuel hose going out - and that's it ! .. must be a
vacuum port behind/under where it's mounted ?
Also a good cleaning around the carb linkages.
I bought a can of SeaFoam yesterday to try in the gas tank.
John T.



Finally got a-round-tuit today.
Dumped some Seafoam in the tank and gave it a good shake-up.
Started the motor & gave it a few minutes of running - revving it up
several times. This was just to get the Seafoam into the carb.
Let it sit for a few hours while I trimmed with the little push mower.
Started it up again - not much difference - so I revved it out
some more and shut it down.
Removed fuel hose from tank outlet and forced some air
back-flushed back through the valve into the tank
using a big plastic syringe. Flushed the fuel hose from fuel pump
to tank outlet ; partly removed the fuel pump & cleaned crud
from around the outside / backside ; tapped & wiggled the fuel pump
to clear any debris ; removed air filter housing - I should have
taken a photo of the years of crud build-up around the carb !
Clean shop-cloth into the carb top to keep it clean.
Used the shop vac & old toothbrush to clean it up ; a drop of oil
on the carb throttle linkage - considered pulling the top off the
carb - decided to see what these preliminary efforts would do -
- put it back together & it wouldn't fire ! AAgggh !
Took a sanity break & looked for the simple things - noticed the
coil plug-wire that I removed wasn't fully seated - duh.
It fired up and ran like a champ - mowed the lawn on even revs -
... at fairly low RPM which was not possible before.
I'm still pretty happy with my 1990 lawn tractor.
It will still need some re-build work - for the next 30 years -
: carb-job
: all new rubber lines fuel ; vacuum ; hydraulic ;
Rock solid engine & tranny - if I am any judge.
... I think I'll keep her ..
John T.


Good work! Perhaps someone will learn from your experience.

As a side note, I was told to always mow at max rpms to have the fastest tip
speed at the blades.

--
Tekkie