400 King Quad 2008 4 stroke motor issue

Birdsnest

Birdsnest

Well-Known Member
Well I know that this is pretty far off in left field for this forum but I've witness such miracles as such here before.

I have this 4 stroke motor on this(2008) quad that seemed to stop running when it was running hot. The fan was not coming on. In the meantime I have wired a switch to the fan to just run it during use.

When hot it would not idol or run hardly at all and I would let it sit for a while and off it would go and I would just go fast to have lots of air cooling it.

My first thing was to test the thermal fan switch. In a pan of hot oil i found that it switched on a 200f. From what I found on the net, and I could not find much, this was a bit hot so I put in a new temp switch and i tested it and it switched on at 160f so I thought that was it. Nope.

I idled the motor in the yard with the new thermal fan switch in until it got warm and it started running rough again. At this stage I checked the temp on the rad and the block. Both temps were 132f so the motor is not over heating. FYI the over heat light never came on during any of this. I was going to replace it too. Glad I didn't.

So the question is what is causing this rough running at the not too hot running temp. It coughs and sputters and has no power and backfires. I was told by one professional that it could be a coil failing at the temp of 132f.

Thoughts?
 
That's good advice. Sounds like an intermittent electrical problem. Backfires usually means spark timing, or strength. Could be lean fuel as well, so check fuel line routing so its not touching anything hot. Check spark plug leads.
 
island idiots said:
That's good advice. Sounds like an intermittent electrical problem. Backfires usually means spark timing, or strength. Could be lean fuel as well, so check fuel line routing so its not touching anything hot. Check spark plug leads.
Click to expand...

It only happens when reaches that temperature.
 
I forgot to mention that I did check the wireing for the fan switch by closing the circut with a paper clip as the thermal switch would do. It all was fine. Fan came on no problem there.
 
back probe the temp sensor and see if it shorts at that temperature causing the fuel curve and timing to change, you can test the coil buy grabbing a rag and ice cubes to cool the coil once it starts acting up
 
I'm not sure what "back probing" is. The over heat(light) sensor or the fan sensor?
 
take a paper clip and slide it alongside the weatherpac, to read the voltage return from the sender while leaving the connection together
 
OK but which sensor. There are two. One for the fan and one for the over heat light.

Would the over heat light have a limiting function? The light has never come on during all this.
 
I just had the same issue with my sportsman, took a while to find it but it turned out to be the plug wire itself, would only do it with a warm engine,
And got worse when damp outside,
Try and mist/spray lightly the plug wire and coil area with a water bottle and see if it worsens, or you see the spark jumping, night time or a dark garage is best to see it. From what you've said I don't believe you were overheating at all.
I got a bit lucky as you could see mine arcing when it did it
And the strangest thing was it was arcing onto a rubber rad hose? Which I found hard to believe as rubber is non conductive,
I replaced the plug wire but ran it inside a piece of wire loom this time, and should add the only code in the efi computor was for the crank poistion sensor, which was new and ohmed out perfectly, but code kept coming back, plug wire was the cause
 
Last edited:
ok that changes things as i figured it was efi, you can cool the coil with ice cubes, but likely a cdi or possibly spark plug wire
 
Alrighty then. I will look into these things today. Thanks so much for the help. I'll keep ya posted.
 
Update: I could not find any arcing or could not stop the event by icing the coil.

I was out with the quad doing a 10 km climb into some alpine with the fan running and at about 6km it totally died. No cooling helped the situation. I was lucky to be with a buddy who towed me out.
I took it to a shop where they informed me the coil was fine but the carb was flooding the cylinder chronically. They did n0t know why it would be related to reaching a certain temp. They serviced the carb and put it together and could not duplicate the issue I was having.
I took it out and ran the **** out of it with the factory fan configuration and it did not repeat the original issue. The fan never came on but it may not under those running conditions.
While the issue seems to be resolved I did not get solid info on what exactly was going on. I hope it is fixed. I guess the reality is however far you drive be prepared to walk out.

Thanks for the feed back folks.
 
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