[mshearne]

We have a 2005 Mule - KAF400A which is running badly. We had the carb replaced about 6 months ago and it ran fine for a while. Then it started acting up like it did before. We found gas in the oil several times and ended up getting a new carb for it. I put it together and it started fine. Blew a lot of smoke for a while then seemed to run fine again. Then a day later, after the engine had been running for a few minutes it started running roughly and trying to die. It would restart, but die again, and backfire. Friend told be to clean the spark plug, so I did but didn't get any better performance.
Any suggestions on what I might try. Does the carb need to be adjusted in any way?

 

[Mule055]

Seems like the 610's have problems with the carbs fouling the plugs.... What color was the smoke it blew out?

 

[mshearne]

Smoke is white or a very pale blue that looks white.

 

[Mule055]

if there is water contamination it can blow white smoke... but a blue tint may be oil,.

 

[mshearne]

New development on the UTV. Now it won't start at all. We have installed a fuel cutoff in line and I made sure it was open, but the engine just wont kick off. It seems to me that the starter is not turning very fast. Checked the battery and made sure it was ok. A little low on amperage, but within range on the battery load tester. The fuel pump has been replaced recently because I had this similar problem before.

 

[Mule055]

remove the spark plug or air filter boot from the carburetor, spray some starting fluid, carburetor cleaner, or even a small amount of gas in it,
if you took out the spark plug, reinstall it, then try to start, if it runs then dies, it's a fuel issue. have you check to be sure the pulse tube is connected to the engine block?
or you could also remove the fuel line at the carb and crank the engine over to be sure it's pumping.

 

[mshearne]

Tried the starter spray and no results. Didn’t even try. Just turned and turned. Still think it’s turning too slowly. Hooked up a deep cycle marine battery to it and it will barely turn over.

 

[Mule055]

your starter may be bad if you hooked up a deep cycle battery to it and it still wouldn't turn over faster.

 

[mshearne]

your starter may be bad if you hooked up a deep cycle battery to it and it still wouldn't turn over faster.

The same thought passed my mind also. I was hoping to avoid this but have been replacing starters on most all of the UTVs at the ranch. The Mule, the Ranger and the Gator have all had starter issues. Especially the Gator.

 

[cookie_monster]

u can't clean spark plugs no more replace only

secondly gas in the crankcase doesn't necessarily mean that the carb is bad. The fuel pump is a pulse operated pump, the pulse comes from the crankcase pulsing as the engine is running. If the diaphragm is leaking gas will get into the oil

lastly and frankly the most common cause of gas in crankcase is....normal. Yeah it's normal. For those that don't know all Mules other than the MX and FX/T's are all powered by industrial engines. Industrial engines were designed to start, then run at 3500 rpm (+/-) for hours on end, at full load. Well on a lot of these Mules, they start and idle and shut off then start and idle or go real low speeds, then shut off, restart, same thing. So what happens is.....the lube oil in the crankcase never gets hot. There is normally always going to be some combustion vapors that get into the oil, it is considered normal on any internal combustion piston engine gas diesel or whatever they are not perfectly sealed. Over a period of time which can vary, those vapors build up and the oil level rises, because it has fuel in it. Remember, almost all engines since 1980-ish have a closed crankcase ventilation system, in that on the Mules (most of them) the crankcase vent is plumbed to the carburetor or air intake in a way that any oil or vapors in the crankcase are burned. So on the 610/sx/etc when the oil level gets too high with fuel vapors it pukes the vapors directly into the crankcase vent, which goes to the air intake on these, where it's ingested by the engine and "burnt"....making the engine run RICH, resulting in FOULED SPARK PLUG(S), smoke sometimes, poor running etc.

The cure? If you use it that way (frequent start stops lots of idling and low speed operation), use low gear. It's just another gear in the transmission you won't hurt anything. If you're going to the mail box about 300 foot or so (or whatever), in low gear just throttle up and let it run on the governor once in a while. It's designed to run that way (industrial engine) you won't hurt it and frankly it's probably better for it---and I know, you're gonna say heck no I ain't racing my Mule, I don't want to wear it out. Fine. Deal with gassy crankcase.

 

[mshearne]

Wow! Awesome information. I’ll get a new plug. Explains why I see oily residue everywhere.
Something I noticed yesterday- a black puddle under the muffler and black on the muffler. This thing hasn’t been run extensively for a number of months because of starting issues. The operator of this one usually drives slowly and lets it idle for long periods of time because she is afraid it won’t restart and she will be stuck out in a pasture a mike away from the ranch.
im sure there is more than one problem which makes it harder for a non mechanic.
one thought that ran across my mind was the fact the carb was replaced about a year ago with an aftermarket based on the limited information we had on the bike. Is it possible to come up with the wrong ID for the bike? Like, what if it is something other than a KAF400A? The serial number stamped into the frame is badly worn down.

 

[Mule055]

These are all the 2007 and prior KAF400_____ models, they all use the same 15004-0953 carburetor.

 

[mshearne]

Thanks.