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Hi Guys, hoping you can help me with a problem I’m having with my 2006 Outlander 400. I’ve read quite a few threads on this forum and others regarding overheating issues with these machines but my situation is a bit different and I haven’t been able to find much pertaining to this so if you can help me out its greatly appreciated.

The problem is that when the machine gets hot, it sputters and dies. I can keep it running if I give it a little choke but eventually I can smell gas (flooding) and it dies out again. If I turn it over with throttle fully open I can restart and through this process I am able to limp it home. When the machine cools down again, it starts and runs perfectly.

Some of you may be thinking this is a carb issue. Well, I have had the carb completely part and it is perfectly clean. I have also replaced the fuel pump fairly recently and checked the valve clearances and all is within spec. The reason I don’t think this is a carb/fuel issue is because when the machine is cooler it runs like a top. It starts perfectly, idles perfectly, runs and pulls strong. In the winter I never have this sputtering problem, only in summer on hot days or on rides where the machine is really run hard and it heats up a lot. I’ve also investigated the idea of a faulty gas cap that does not vent properly thus creating a vapor lock in the tank but this is not the problem. Another example: last week I was riding in +30C weather, the machine starting sputtering, I was able to get to a creek which I parked in for a couple of minutes with the machine off. This cooled the machine enough that it ran perfectly again for another 20 minutes before the same problem started. This furthers my belief that this problem is strictly related to overheating.

As I understand, one of the symptoms of overheating is sputtering and dying, which is my situation. However, none of the other typical overheating symptoms are present. The overheat light never comes on and the fan cycles on and off periodically as it should. The coolant in the rad has never got so hot that it has steamed.
This leads me to wonder if the problem is related to the temp sensor. Would a faulty temp sensor possibly explain this situation? I’m thinking something along the lines of the fan not engaging soon enough or for long enough? Is there a thermostat on this machine? I looked at the parts diagram but don’t see one listed. Would a faulty thermostat prevent the maximum coolant circulation allowing the machine to still run slightly overheated? What about a faulty water pump, this would also prevent the most efficient coolant flow? I know I’m going to have to start testing some of these components but would like some suggestions on what to try first and if you think I’m on the right track with this? Thanks in advance.
 

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If the temp sensor is a BRP original part , I doubt it has lost its calibration somehow. If someone installed one from another vehicle, that may allow it to overheat .
The only thing that comes to mind to correlate the sputtering with overheating is fuel boiling in the bowl .
When I had my little 4 hundo , every fall I used to yank the radiator and soak it in HOT water in my laundry tubs.
Unbelievable how much stuff came out of there even after it was "cleaned".
 

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If your cooling system is functioning as you say, I can't see it contributing to your fuel issue- there's something else going on.

I wonder if your bowl preheater is perhaps stuck on, is it even connected/operational?

Talking about the carburetor, I've read so many guys say the same as you "I've torn it down/cleaned it/rebuilt it", but not everyone is aware of that little last chance screen hiding under the float, have you removed it and verified it isn't gummed over from fuel line deterioration? I wonder if you don't have a little split or tear in the boot that essentially makes up your "intake manifold", or in the vacuum signal from it to the fuel pump, that expands and opens as ambient temps climb....

Again- I wouldn't go changing cooling system components- water pump, tstats, sensors, as that part of the bike appears to be functioning as intended.
 
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Discussion Starter #4
Thanks for your input. Yes, maybe it is a fuel issue but I am all out of ideas when it come to the fuel issue at this point. I know about the screen under the float, it is perfectly clean. Where is the boot your talking about and the vacuum signal and how would I check that? Maybe your onto something there.
 

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So just like there's a connector boot between the airbox and the carb, there's also a boot between the carb and the cylinder head. It's got a little port on it that the fuel pump gets its vacuum signal from, via a short little run of hose. Perhaps somewhere in there, you've got a split/tear, that engine heat exacerbates?

I went back and re-read your initial post, and something jumped out at me: when you choke it to keep it running, that tells me it's sucking in air that it wasn't expecting to, ala an air leak somewhere. Hopefully you sort it out.
 
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OK, so I finally had a chance to investigate your suggestion re: the boot connecting the carb to the engine and the fuel line that runs from that boot to the fuel pump. I took the airbox and carb off and removed the boot to have a look. It appears in perfect condition. I also inspected the hose running to the fuel pump (very short hose), there were no rips/tears and the connections at each end were good. The clamp holding the carb onto the boot itself and the bolts that hold it onto the cylinder head were also all good. Is there anywhere else that an air leak could occur?
 

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Man I'm running out of ideas here......I've run my old 4hundo in triple digits for many hours, and the ambient temp didn't make a difference.....

There is, of course, a delay, between the time that the fuel fills the bowl, and the engine depletes it, just based on throttle/load/etc. That delay could easily account for the time between engine cold and warmed up. Have you tried running it on both "on", and "reserve" on the fuel valve? Just trying to rule it out as contributing, somehow.....
 
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Have you checked compression? Maybe compression is at the min so when it is not completely heat soaked it is enough to run fine but once hot the cylinders expand enough that it decreases. Just a thought
 
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