KQ stutters and stalls

[northwest Texas]

Hey Josh, since youseem to be the only guy around this forum, I need to pick your brain.

The other night, I was about 100 yards from home when my KQ700 died. At first I thought I was out of gas but was only low. I managed to get it fired back up and limped to the barn where I added a couple gallons.

It was still hard to start and once going, felt like an old carbureted engine that was getting too much gas. It would barely pull itself to 20mph and wasn't any better in low.

My FI light hasn't come on in the dash but I added alittle carb cleaner and ran it but it still hasn't helped. I can start it up cold and it runs about a minute fine and then just dies and is a bear to start after that (since the other night) Try to rev it and I really have to feather the throttle and it will start stuttering and popping out the exhaust.

Flipping through my service manual last night, maybe a vacuum line has come loose?

Until then, other than taking a long time to start cold, she hasn't skipped a beat in the 50 +/- miles I've put on it since I've had it (05 model) and it was just fine the 10+ miles I'd been riding it earlier in the day and that evening.

[firefighterjosh]

How many miles/hours are on it all together?

Have you changed out the stock filter?


I would check a few things. First make sure the air filter is clean. then I would change the plug. Also make sure the boot on the plug wire is making a good connection. When you pull the spark plug boot off make sure there isn't a ton of mud in there. I would also spray it with dielectrical grease.

Have you relocated the gas tank vent tube?

If it still runs like crap and you haven't changed the vent tube you may have gunk in the tank. You can see the vent tube vavle (orange) under the left side fender. (drivers side in a car). You can grab it and pull it out. Make sure it clean. Sometimes it will fill with dirt and let in a bunch of mud. If its not working or is stuck open it might be time to pull the tank and check it out.

Its not really too hard to get off. I had my tank out within 1 hour.

hope this helps

[northwest Texas]

Thanks, I'll give it a check next week hopefully.

What gets me is it was just sudden, just like it run out of gas and it wouldn't start hardly.

I'll check the vent tube as per the manual as well. Hopefully it's just something as simple as that.

The quad has about 4300 miles on it now. Here in this neck of the woods, guys put 10,000+ miles on their quad checking irrigation engines and sprinklers.

[firefighterjosh]

Let me know what you find good luck

[4trax250x81]

I would also check the vent tube for the fuel tank. It sounds to me like thats the problem, that would be my first place to check.

[northwest Texas]

Ok, here's the deal. It fires up just fine initially and will idle fine for a couple minutes before it dies.

What it acts like is if it's not getting fuel to the "carb"

I blew back through the vent tube and it was free of obstructions. So then I thought maybe the gas cap was maybe the problem.

It doesn't matter if the vent line is on or not, nor does it matter if the gas cap is on or off, eventually, it will start coughing and sputtering from what seems like it starving for gas.

So where next? I'm sure the fuel pump is pumping enough fuel initially because after a few minutes, it will fire right back up and rev fine before "starving for fuel"

After it starts "starving for fuel", you must give it several minutes before the symptoms go away and it fires up cleanly.

A couple years ago, I didn't notice I had a kink in my gas cap vent hose on my 400EX and it would run but not great. It'd fire up and run great until there was a vacuum and the carb couldn't get the gas out of the tank. This is almost identical to that, if you understand me now.

[firefighterjosh]

If you took you gas cap and vent tube off that must not be the problem. My guess would be is that it has gunk in the tank.

Its really not too hard to look at.

Just take the rear rack and plastic off and the tank is right there.

You will see (i belive white) screw on lid that would screw right off and take a peak at your fuel pump and bottom of the tank. If theres dirt I would suggest taking it out all the way and cleaning it.

[firefighterjosh]

BTW you can see the lid on top of the gas tank in this pic. It looks like it will srew off.

[northwest Texas]

I already have the rear fenders off and see exactly what you're talking about. It looks like the pump will come right out.

Bad thing is I just poured 2 gallons in there when this all started.

I hope you're right that there's just a bunch of junk plugging the intake preventing sufficient fuel getting to the combustion chamber. You would think though that with all the shaking I've done on the thing some of that might break lose and it would run right, maybe for a quick drive or something.

But a couple years ago, I had some clutch plate start flaking and they would plug up the screen partially on my tractor and the only way to fix it was to drain the transmission, pull the screen and clean it off and get out what I could through the hole and do it again. After about 3 or 4 times of doing that, I haven't had any more trouble (knock on wood)

That might also explain why at 62mph it would start cutting out like it was hitting the rev limiter and it was starving for fuel. It was fine at 61mph but at 62mph it would act up and not go any faster.

I'll try to take a look at it tomorrow.

[firefighterjosh]

While your at it I would relocated that check vavle too. I ran mine on top of my air intake