Riding mower loses power

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
Got a John Deer X300 mower from a friend. Has a 472cc Kawasaki engine.
Aparently as it warms up, it loses power until eventually dying. Used to go about 30 mins, he parked it in the fall. Now it only took ~7-8 mins, barely enough to get on the trailer, where it sits now.
As I understand it he has to open the choke completely to keep it running, like I said when he loaded it up up, by the time it was at all warmed up he had to have it wide open just to get up his yard close to teh trailer.

I don't know anything else, aside from the gas is decent etc. I haven't had a chance to dig into it yet due to bad weather, and dummy me forgot to get the key from him o_O which I will in a day or so.

Where to start? I'm thinking a seal somewhere is bad and its slowly increasing airflow as it warms. Seems to start OK, aside from dead battery, so it's not an opening in fuel line
 
I'd look at fuel system, fuel filter, cracked fuel lines, bad or weak fuel pump if equipped, don't over look a plugged fuel cap vent
 
Vapor lock is one I'll definitely consider. It's easy... clean the cap, or just run w/o it ;-)
But wouldn't those other htings make it hard to start, or not run well in the first place?

My current old mower has a leak somewhere in the fuel line. It runs fine, but if its been sitting > a day, it takes a litle gas in the carb to start b/c it evaporates out.
 
RatLabGuy said:
Vapor lock is one I'll definitely consider. It's easy... clean the cap, or just run w/o it ;-)
But wouldn't those other htings make it hard to start, or not run well in the first place?

My current old mower has a leak somewhere in the fuel line. It runs fine, but if its been sitting > a day, it takes a litle gas in the carb to start b/c it evaporates out.
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debris in the tank at fuel pick up can cause a gradual starvation issue, Draw on fuel pickup pulls debris in, the more the draw the tighter and more debris. the draw stops, debris drifts away until draw begins again.

ive had diesel lifts with small mud balls (turds) of rust and dirt floating in the fuel, no sock on the pick up, fuel level gets just right and the intake tube draws the ball in. Motor dies out or quits all together. Fuel draw stops, mud ball falls out and will run again....until it gets sucked back in.
Have had wasps, stink bugs, bees, cockroaches all blocking fuel systems gas and diesel. Leaves, dirt, random other things. Had one machine they would not let me pull the tank for cleaning, every other week I’d go out and blow the fuel line out from filter back to tank to unclog the sediment in the tank.

Water in fuel, gas or diesel will cause an algae bloom and that will stop up filters and pick up screens.

Today’s gasoline is shit, it breaks down rubber fuel line internally, let alone dry rot externally.
 
Clean the carb and check the float and needle, the rubber tip on the needle can swell and not allow the bowl to completely fill. Had this happen on my boat.
 
Mulishajoe said:
Clean the carb and check the float and needle, the rubber tip on the needle can swell and not allow the bowl to completely fill. Had this happen on my boat.
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It'll also get gummed up with wax... or whatever that shit is that precipitates out of the gas.
 
Could be electrical, like a coil breaking down, or something. But more chance a fuel problem. My mower ran out of gas, a week ago, as I forgot to check it. I was on a hill. Refilled it, & had a hard time starting it. Then it had the sputtering thing. Ran decent wide open, & with blades on. Barley ran at 1/2 throttle [needed choke], & wouldn't idle. A good dosing of "Mechainic-in-a- bottle'', Didn't cure it. I pulled the top off the carb, & probed every hole I could find with torch tip cleaners. Tried taking the 1 jet out, but it wouldn't come all the way. Screwed it as far as I dared & probed it too, then screwed it back down. Very Small amount of sediment in the bottom of the bowl, which I cleaned out. What ever it was, I must have hit it. Runs Fine now! Changed the fuel filter, while i was there too.
 
Well I at least got it started and listened.
First, it isn't the cap... b/c it dosn't have a vented cap ;-). I think it has a seperate vent line. Will have to inspect it.
Once cranked, it ran for the 10-15 mins I was tinkering. It was revving up then dying back, oscilating back and forth. With enough throttle, like pretty much all the way up, it would just about even out, but at low throttle it would have a hard time idling. Opening the choke would help a little but only just the right amount
Som yeah, I think its a fuel delivery problem, something probably restricting flow. It has a clear inline filter, it looks ok but tomorow I'll pull it and check.
 
RatLabGuy said:
Well I at least got it started and listened.
First, it isn't the cap... b/c it dosn't have a vented cap ;-). I think it has a seperate vent line. Will have to inspect it.
Once cranked, it ran for the 10-15 mins I was tinkering. It was revving up then dying back, oscilating back and forth. With enough throttle, like pretty much all the way up, it would just about even out, but at low throttle it would have a hard time idling. Opening the choke would help a little but only just the right amount
Som yeah, I think its a fuel delivery problem, something probably restricting flow. It has a clear inline filter, it looks ok but tomorow I'll pull it and check.
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UncleWillie said:
Pour seafoam into the carb til it once flows. Let it sit overnight. Remove sparkplug. Crank til carb is cleared. Reinstall plug. Attempt to start. Works 97.4% of the time.
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Seafoam is good, but I prefer Mechanic in a bottle! First time it Didn't fix my problem! After I run my tip cleaners through all the jets & air holes, it was fine. And I Never run ethanol, Non-eth, Only.
 
Ok, let me find out which variation of the X300 you have. Does it have a flat air filter, or the top mounted canister style with a hose clamp?

Since you say it's surging, you need to take the carburetor off and inspect it. I have seen fuel be the culprit, but Kawasaki's have a lovely habit of losing the welch plugs on the top, giving an unrestricted air bleed. If they're all intact, open it up and get the jet and emulsion tube cleaned up with torch tip cleaners. You'll probably need gaskets and such, so be prepared for that. Don't mess with the governor just yet. Clean and reclean. Kawasaki's are usually very responsive to a decent cleaning.
 
maulcruiser said:
Ok, let me find out which variation of the X300 you have. Does it have a flat air filter, or the top mounted canister style with a hose clamp?

Since you say it's surging, you need to take the carburetor off and inspect it. I have seen fuel be the culprit, but Kawasaki's have a lovely habit of losing the welch plugs on the top, giving an unrestricted air bleed. If they're all intact, open it up and get the jet and emulsion tube cleaned up with torch tip cleaners. You'll probably need gaskets and such, so be prepared for that. Don't mess with the governor just yet. Clean and reclean. Kawasaki's are usually very responsive to a decent cleaning.
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Flat filter on the front.
FH491V engine
 
rodney eppes said:
Seafoam is good, but I prefer Mechanic in a bottle! First time it Didn't fix my problem! After I run my tip cleaners through all the jets & air holes, it was fine. And I Never run ethanol, Non-eth, Only.
Click to expand...
I have gotten so many riders for scrap that would try to start, or ran badly, or surged. I have had excellent luck with the overnight seafoam trick. ON the ones it didn't fix it at least got the crap out of the carb before I pulled it apart.
 
I didn't have any seafoam, need to pick some up and try it. I did however take the air intake off and spray a whole ton of carb cleaner in, let it sit awhile. I think that helped a bit, it wil lrun steady on half throttle or more, anything less and it surges. When surging if I choke it just right it wil leven out, so I think it's definitely just not pulling quite enough volume to do the job. Got it off the trailr and drove aroudn awhile at ful lthrottle, it seemed to run ok, but even at 100% isn't terrible fast. I have the impression the overall RPM at max it's as high as it could be. I assume there's a spec for what that should be?
 
UncleWillie said:
Most mowers run around 3600 rpm.
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just looked it up, this seems to be it. At least thats the RPM its rated at 17hp.
I suspect I should be able to take the cover off and time the fan w/ my IR gun
 
Looks like at half throttle it running ~2400 RPM, at full its about 3200. Now, I haven't checkedt he governor or anything yet, but I'm guesisng whatever the restriction is is keeping it from a full spinup.
 
I have an older john deere 240 Kawasaki,i have been fighting this same issue last year and this year. First it wasn't charging, ended up being loose connection at voltage regulator. fixed this and it ran great for one mow and then was back to surging (after about 10 minutes of start up). Terrible surging on any type of hill until it would eventually die or just run on choke. While cleaning the carb again i noticed the vacuum line on the fuel pump was kinked, fixed that tonight and so far so good. It ran the best tonight that it has since i bought it about 4 years ago.

Mine is a "special" mower supposed to have a 14hp, now it has a 12.5, throttle cable isn't correct.. etc The PO must have took 3 mowers and made one lol thats why i wasn't sure where to start and wasn't even sure if it was the correct carb on the mower.
 
Mid last week I got some seafoam, poured it in carb, let it sit overnight. Next day, it cranked and ran pretty smooth, but again only at full throttle, at half it would still rev then back off, unless I gave just a hair of choke, then would be fine at half throttle.
So I poured a good bit into the tank. Waited a day, dranked it up. Boy it ran even worse then, would oscilate at even full throttle, needed some choke. I figured, damn maybe I put too much seafoam into the tank, actually decreased the gas % too much. Let it run awhile but no improvement. Well crap now I gotta drain all that.
Then Sunday, after sitting several days, I cranked it again. Low and behold, after blowing smoke awhile... it leveled out and ran pretty good! Back to a bit better than before.
So, gotta give @UncleWillie credit - just sitting w/ the SeaFoam for a long time did the trick.

But then I got to thinkin gabout the original problem - buddy said after 30 mins it would just have no power and die.
So, I pulled the plugs.
Turns out, both were pretty fouled (very possibly from the Seafoam treatment) but one was way over spec on gap, the other a little.
Got 2 new plugs, popped in... now it runs liek a champ, no choke needed whatsoever.
I suspect the old gappy plug would expand and when hot and just go past the threshold of working decently.

Now the only remaining thing is, it still idles at ~3240 instead of 3600. Not sure if that is even a problem.

btw @maulcruiser I checked the welch plug, it was still in there pretty tight.
 
20200510_181346.jpg


This certainly didn't help.
 
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