2005 Kawasaki Mule 610... sputters going uphill

[w_r_e 2]

Well, after tinkering on my last project (a 2003 Kawasaki Bayou 300) I ended up putting it on Craigslist and it sold within a day. Then about two weeks after that a 2005 Mule 610 with 40 hours on it popped up, for about 1/3 the cost I usually see them, so... I didn't have much of a choice.

The Mule's first issue was idle, it would die if you didn't keep a light toe on the accelerator. Turns out the idle screw had never been touched, five minutes after I got it off the trailer it idles just fine. 🤦‍♂️

As of today, it runs great on flat land. And it climbs like, well, a mule.

But it has one issue. Sometimes uphill it will suddenly lose power like the fuel isn't getting delivered. It never dies completely, it just sputters and won't go until you let off the gas pedal and let it recover. It tends to do it more with 2 passengers or some cargo and wide open throttle BUT occasionally will do it at only partial throttle and with just me on it. 

I read a lot about how the fuel pumps on these Mule 610's suck, so I put in a new one today and a new fuel filter. It still had the same symptoms immediately after, so that was $40 wasted.

Any ideas? I keep seeing folks saying they replaced the pulse pump with an electric fuel pump. This thread said so, and it gets brought up in this thread and also here. In each case somebody says "12v fuel pump solved my problem!" and then they promptly disappear from ever posting again, lol.

I have some questions for y'all:

1. Do you think fuel delivery is the problem? I have a hunch that it is, given the hill + throttle symptoms.

2. The pulse pump on the Mule is located ABOVE the gas tank. Can an electric fuel pump pull fuel UP in this manner?

3. What would I do with the spare line that goes from the fuel pump to the crankcase? Every electrical pump is just in & out, they don't have that third line...

4. Any idea what kind of flow rate I would need or which pump works for this application?

 

[MarkinAR 123]

Sounds more like carb is dirty or float level is off a bit not allowing quite enough fuel in the bowl.  I'd give the carb a good clean and adjust the float to spec before buying any more parts.  My dad has a Mule and it tends to be a bit cranky with similar symptoms...and his is just a dirty carb.

[w_r_e 2]

@MarkinARthanks, I picked up some carb cleaner this morning and will give it a spray and see if any symptoms change. In the service manual I have for this model it says "float height not adjustable."  

You are right that I jumped ahead of myself with the fuel system parts, but seeing multiple folks saying that they had issues with the fuel pump and switched to electric really got me convinced that that was my problem too. I ordered a cheap electric 12v pump and will have it on hand if the carb cleaning doesn't help...

[MarkinAR 123]

Keep in mind a thorough cleaning means removal and disassembly. Pretty sure a properly cleaned carb will solve your issue. Its fortunate the float isn't adjustable so it can't get out of spec. Honda 300 is the same way and it's great. 

[w_r_e 2]

Yes, that is true. I do need to pull the carb and rebuild it, at some point. I did spray some cleaner in there, and the uphill stall-out was identical to before, for what it's worth. Also, when I put on the new fuel pump yesterday I used a clear line from the filter -> pump, and I see about a 1-inch long bubble in there. I got the bubble out, but once I ran the hill again and it nearly stalled, the bubble was back. To me this says I'm pulling air back into the fuel pump from the crankcase.