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2007 Honda 420 Overheating & stalling

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It seems like a gas problem but I've changec, fuel injector, gas cap. I have lots of fuel pressure but after four wheeler has run for 20-30 min I have no power and sometimes stalls and won't start. Any ideas?

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Sounds like a CDI issue, when they start to go, sometimes they only show symptoms after they are warm. Is it excessively hot where you live, when I think of Canada, sweltering heat is not the first thing that comes to mind. If it truly is an overheating issue, first thing to do is make sure that your radiator is not clogged with dirt and mud, make sure that air can flow freely through the radiator. Also, make sure that the cooling fan works. If it doesn't, try hooking it straight to the battery so you can determine whether the fan is broken or it isn't being told to turn on, possibly a sensor or wiring problem. You may want to check for intake air leaks. There is a throttle position sensor on the side of the throttle body, make sure it is plugged in. There is an air tempurature sensor in the airbox, make sure that that is plugged in and clean, also make sure there is not damage to the wires running to it. If the weather is really hot there, you may consider installing an external oil cooler if it doesn't have one already. Running a higher octane fuel will help the engine run slightly cooler. Good luck.

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The radiator is clean, antifreeze is full, there's no air locks in the coolant system and the fan runs but did find a mouse nest in my airbox so will check the sensor in the airbox. Any other ideas?

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Too lean???

Hows that sensor in your airbox? Thats yer iat sensor, tells the computer the temp of the intake air and adjusts jetting accordingly, if thats shot, that will cause a lean condition and overheating. Do you have an idiot light on your dash ? I assume so. When you turn your key on, that light should be on steady and then go off. If it doesnt come on, stays on or blinks, you have a sensor or possibly worse problem.

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When the machine starts acting up, pull the plug and see what the spark looks like, you should have a strong consistent blue spark. If the spark is inconsistent or looks weak, I would suspect a CDI problem, but would test all of the ignition components before you start replacing things. If you have a decent repair manual, there will be directions and specs for direct resistance tests that you can perform on some parts with a multi-meter.

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same problem in fl. overheats, cranks over but will not start, new thermostat, radiator clean ,fan working, air box sensor clean and plugged in computer shuts down fuel pump, will start after 3 or 4 days HELP

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I have similar problems.  My Honda trx 420 starts great and runs until it gets warm (hot).  Then it runs at an idle but when I try to throttle up it bogs out.  If I shut it off and let it cool down (maybe 5 minutes) it will start and run great.  May run 1/2 an hour at 60 degrees and moving at 15 mph.  We have cleaned air filter, changed the oil, washed entire machine especially the CDI unit.  Any suggestions?

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Sounds like you have either a bad thermostat, bad cooling fan or the fuse/wiring going to the fan has a problem  or possibly the sensor that brings he cooling fan on.   

Lastly is the water pump could be bad not circulating the coolant through the engine.  

So what I would do first is if you are good with electrical testing you should locate the fan sensor  it should be on the radiator with two wires going to it. Turn the key on and jump the two wires together and the fan should come on. If so that rules out the fan and the power going to it as far as any problems.   

Next would be the sensor not working properly by reaching temperature. That’s done by taking the sensor out and putting in hot water and testing for continuity on the two metal wire connections on the sensor. You need a thermometer to see what your water temp is (185-190) should close the sensor, a pot of water on the stove works well. If the sensor has no continuity when it’s cold and it does after putting it in hot water then it’s fine. Some people don’t bother with a test and just put a new one in. 


Thermostat: I would order a new one and gasket (most likely your problem)  i always keep one on hand. 

Water pump: usually leaks when it’s bad but agin never know. I always keep one on hand just in case. 

Other then that make sure you have coolant in the system and there was not a leak your unaware of and don’t run the engine any more since the high temps can do damage to the cylinder and head gaskets. 

Double check your oil for any discoloring like coolant or water is in it.

lastly did you happen to see any white smoke coming from the exhaust? This would mean your head gasket is bad. That could have been done from running the engine while it was over heating. 



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