520xi Ch20s engine Loss of Power

[STEVEN H GEORGE 0]

Help Needed on 520xi Toro Wheel Horse 

I have a 1999 Toro 520xi,  Model 73540 with CH20S , spec 64583 engine.   It starts and runs fine without the PTO engaged or moving on level ground.  But if I go up a steep hill OR engage the PTO,  it loses power.   So far I’ve changed the fuel filter,  spark plugs, air filter,  replaced battery,  emptied out and refilled the gas tank.  Also, took off the deck and found all the spindles spinning freely with no binding.   But no change.   NOTE:  When I changed the spark plugs I noticed they were covered with black soot.   What am I missing?

[Jeff-C175 7,206]

Sounds like you have two different problems.

 

Something wrong with carb, possibly the float,

 

And

 

An issue with the safety interlocks, possibly the seat switch.

[STEVEN H GEORGE 0]

I can believe it might be a carburetor issue.  On my model the seat switch is part of the starting circuit.  The mower starts fine and runs all day without hesitation.  It has a problem only when the engine has a load on it.  

[Jeff-C175 7,206]

6 minutes ago, STEVEN H GEORGE said:

I can believe it might be a carburetor issue.  On my model the seat switch is part of the starting circuit.  The mower starts fine and runs all day without hesitation.  It has a problem only when the engine has a load on it.  

 

Maybe it would be a good idea if you elaborated on the exact meaning of "loses power"

 

Does the engine quit, die, stop?

 

Your seat switch is also tied into the PTO circuit.  If you are not in the seat or if the machine 'thinks' you are not it will kill the engine when you engage the PTO.

[JoeM 8,334]

If your fuel system checks out you might want to take a look at the ignition modules. 

Some of the kolhers not all had smart-spark or DSAI Digital Spark Advance Ignition

If the timing is not advancing they turn into dogs real quick

Need a timing light to check it out. The instructions are in the description of the vid. 

 

 

[STEVEN H GEORGE 0]

Thank you sir!  Also ,  would you know how to check the rpm of this type engine? 

[Handy Don 14,061]

17 hours ago, Jeff-C175 said:

Sounds like you have two different problems.

 

Something wrong with carb, possibly the float,

 

And

 

An issue with the safety interlocks, possibly the seat switch.

Sooty plugs generally indicate running rich or with plugs that are not in the correct heat range or at too low an RPM. Are you seeing any smoke (black or blue/white)? If so, when?

"Losing power", to my ears, could be that the governor is not properly set to advance the throttle under load or that the linkage amongst the dash board throttle input, the governor, and the carb body throttle is out of whack.

And timing is another possibility, for sure.

I've been happy with a free app on my iPhone called Video Tachometer. It does not follow the changes in RPM but it lets you see when the engine is turning at the target number you set. This works for me because I'm trying to adjust the linkages to get a ~1000 RPM idle and a ~3500 WOT. Other speeds are of no interest to me.

Some members here have had good luck with inexpensive digital tachs bought on the internet with spark plug wire pickups.

[STEVEN H GEORGE 0]

On 6/17/2022 at 10:28 PM, Jeff-C175 said:

 

Maybe it would be a good idea if you elaborated on the exact meaning of "loses power"

 

Does the engine quit, die, stop?

 

Your seat switch is also tied into the PTO circuit.  If you are not in the seat or if the machine 'thinks' you are not it will kill the engine when you engage the PTO.

The engine never stalls.   And always starts without hesitation.  And the tractor cruises normally on level land and does not smoke at all.   Only when I put extra load in the engine (driving up a 40 degree slope or engaging mower deck) does the engine not have enough power to climb a hill or mow.  But it never stalls. I do, however, detect  a little more gasoline smell in the exhaust than before.  

[Jeff-C175 7,206]

18 minutes ago, STEVEN H GEORGE said:

The engine never stalls.   And always starts without hesitation.  And the tractor cruises normally on level land and does not smoke at all.   Only when I put extra load in the engine (driving up a 40 degree slope or engaging mower deck) does the engine not have enough power to climb a hill or mow.  But it never stalls. I do, however, detect  a little more gasoline smell in the exhaust than before.  

 

I think perhaps Handy Don is on to something regarding the governor adjustment.

 

I would look at that first.

 

 

[RED-Z06 2,567]

Verify its running on both cylinders, gassy exhaust and a sudden loss of power under load usually means its running on one hole...a 20hp becomes an 8.5hp