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fatboycowen

518xi difficult hot starts

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fatboycowen

My 518xi runs great, and starts very easily when cold. However, lately, if i start it hot, it's somewhat difficult to start. Takes a bunch of cranks and just the right throttle position. Once it starts it runs a little rough at first, at mid throttle. Full throttle is fine.

 

Where should i start?

 

My research suggests it could be:

vapor lock (haven't tried loosening the cap yet, will next time i mow)

A weak coil. Not sure how to check. I haven't pulled the plugs lately, so i may do that.

Valves out of adjustment causing weak compression when hot - are these valves adjustable?

 

This is the first gas motor that i have yet to mess with the carburetor on, so that might be something to check.

 

thoughts?

 

Thanks.

Jon

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WVHillbilly520H

We'll start cheap and easy spark plugs first ,how may hours on that machine? About every 200 or so hours replace them and yes that Kohler with over head valves are adjustable rather easily from the top kinda like a car with little valve cover on either side of the air cleaner (in the picture) which should also be ckecked and cleaned and or replaced new again 200 hr intervals or less if really dusty the valve adjustment is likely 500 hrs but check the manual if you don't have one they can be downloaded from here by using the search feature,Jeff.

IMAG1743.jpg

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fatboycowen

It now has 570 and change. Bought it with 500. I'll do plugs. I haven't done them yet.

 

I have the owners manual, and can't find any valve adjustment instructions. I've not done a car valve adjustment (never owned one that needed it). Anyone have any kind of instructions or a workshop manual?

 

Do i need to get valve cover gaskets before pulling the valve covers off? I'd assume so...

 

Anyone have a part number for the fuel filter?

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WVHillbilly520H

That would be the Kohler engine manual to show/tell valve adjustment procedures not the Toro operating manual sorry I should have been more specific,Jeff.

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doc724

My 520xi has had its share of hot start problems.   If I shut it down after running for 90 minutes, or so, it was impossible to get started for about 5 hours.  I played around, took electrical measurements, swapped around all three kill relays and eventually changed the fuel pump.  Problem seemed to go away-or at least has not come back.  At the end  of last years mowing season,  the machine would cough and eventually die after running for 10 minutes.  Restarted right away and never gave any further problem for the rest of the day.  Happened again once blowing snow this past winter.  This year I reluctantly bought a new ignition switch ($47-ouch).  No recurrence to the coughing/engine dies so far this year.

 

My point is that this machine is pretty complicated and has the dreaded electrical fuel solenoid.  I never got to root cause on my machine, but I am partial to thinking that the problems are electrical.  The relays are rated for high temperature, but the mating connectors get their fair share of corrosion on them.  Enough corrosion and a high resistance begins to look like an open circuit.  

 

The last observation I have made is that the throttle control does not seem to be linear in operation, meaning you can move it to mid throttle and nothing happens.  All the engine changes occur in the last half of the motion.

 

None of this answers fatboy's question, but at least he knows that others have had issues

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fatboycowen

So, i changed the plugs. They didn't look bad. It runs pretty much the same.

I tested more. When it's hot, just having been shut off, it starts fine, and repeatably. However, if i wait 20 to 40 minutes, that's when it has trouble starting.

 

Does that change anything regarding diagnosis?

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Xearl

As far as I know there is no valve adjustment. I have 98 and it has hydraulic lifters . To be sure I would double check. 

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