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TRX 400 ex dies when hot...

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I want to thanks those in advance that help me out with this.

Lately I've been having some running issues with this thing. When I first start it up, runs fine with no issues. I'll ride it for up to 5 minutes, and when nice and hot, idle begins to drop and eventually cuts off.

Carb has been taken off a few times now to make sure things are clean, filter was cleaned, valves were adj as they were a little loose (when adj it actually took a bit longer to die). For some reason I can't get to the sparkplug...? What else, oh, petcock was replaced, and made sure fresh has was used. When I try to restart it will only start if I give it gas, and when I try to let it idle, it idles really low then cuts off.

But once I let it cool down long enough, it will start up (off the choke) every time and idle, take it for another ride, and when up to operating temps or higher issue comes back.


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sounds like to me its sucking air when it gets hot the motor parts are shrinking and creating a gap or your coil is dieing off when hot weaking the spark it takes a thin wall 18mm socket to remove it becarefull or youll break it the gap is 24-26mm gap.

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I am thinking you have an ignition problem, some ignition components will start to fail when they get warm. Ride it until it dies then pull the plug wire off and check for spark. If there is none, start checking ignition parts, coil, CDI, stator, pickup, plug wire, and all wires and switches in the ignition circuit.

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It's an 05...but got it figured out.

Here's what was going on, after checking things over and over again. Got it running and hot, put the air box back on, and as I went to put the crankcase vent on, it would start to die. Once removed the idle would pick back up. So this whole time, once the motor got up to temp, the crankcase vent hose would pull air away from the carb...

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If this condition is accompanied by smoking/oil burning, then you probably have leaky intake valve guides or seals. If there is no smoke, then you may have a problem with the crankcase ventilation system, perhaps a clogged filter.

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No smoke at all. What else could be clogged? Filter was cleaned, also has the k&n top box with precharger. It's the only hose coming out of the case to the intake track.

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I'm sorry, I did not mean the air cleaner, there is a second blow by tube on the valvle cover, it may have a filter on it, or it may run into the airbox. Either way, make sure nothing is obstructing it. Also, the lower tube that comes out of the crankcase is connected to a catch tank that attatches to the intake tube, make sure that tank is not clogged either.

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