HELP! Nomad Overheating and Backfiring.

[macmac]

I don't know about you Dave, but my days all have numbers and they ain't getting lower.

[Dave]

I know what you mean, Mac. I'm right there, too. :)

[gtucker]

I too have a 99 nomad with a similar problem, It started last year by overheating and every time the temp light comes on the bike seams to cut-out, kind of like it is being limited. I have been told it has something like a safe mode to protect the engine, anyway checked all the usual stuff and in the end I replaced the fan switch and thermostat and it was fine for about a year. Now it has been acting up again and it seems the fan and fan switch is working properly, I wired a manual switch and LED light to it so I could verify when it came on and to be able to turn it on when needed, just in case. Next I bought and replaced the temp sensor, that sets the light, and I thought it was the culprit but after letting it idle and cycle the fan off and on several times, I went for a ride and then it happened again. The temp light came on and the engine stuttered just a little and the light went off and it was back to normal as I quickly went back home. This is been going on for a while and I'm about to give up! Any one have any ideas? Does the bike have an interrupt/limp mode or something that is causing the engine to stutter? One guy posed the idea that the wire to the temp sensor might have a short that grounds out occasionally and assuming when the light goes on the interrupt circuit is activated, if it exist.

[macmac]

gtucker, I have never seen a carb ed Nomad to work on, and so I can only guess. That guess is the harness turns down at cly 2 on the frame, and some wire harness chaff there against the frame. If the nylock tie is still factory it has a release tab on it.

Don't ask how I found that out.

[ringadingh]

Check the wiring harness as Mac suggested, it is a known problem area that has caused all kinds of intermittent electrical problems on some bikes. It usually at the rear cylinder on the LH side at the bottom of the fuel tank, the harness runs along the frame there and sometimes chafes through.
It could also be that your cooling system is plugged up with gunk, anothe rmember had his light coming on all the time, after flushing it numerous times he got the sludge out and his problem went away.

[macmac]

Ring that might be. One way to tell is if a would be hot radiator has cold spots. Colds spots are not exactly cold, but they are colder than hot, and tend to be low on a clogged rad. You can feel this by hand, as un-e ven heat with your hand on a hot rad. Some due caution needs to be applied since this is hot.

[gtucker]

Thanks MacMac and Ringadingh, I will check it out, I did use a digital temp gauge, the gun type you point at it, and it seemed pretty consistent all over and the fluid was very clean, in fact it looked the same as when I put it in last year. Still it could be clogged, and I even wondered if the pump was doing it's job but not sure how to tell? The one thing I can't seem to get an answer on, is if it has some sort of limiter when it thinks it's too hot, as mentioned?

[gtucker]

Thanks MacMac and Ringadingh, I will check it out, I did use a digital temp gauge, the gun type you point at it, and it seemed pretty consistent all over and the fluid was very clean, in fact it looked the same as when I put it in last year. Still it could be clogged, and I even wondered if the pump was doing it's job but not sure how to tell? The one thing I can't seem to get an answer on, is if it has some sort of limiter when it thinks it's too hot, as mentioned?

[macmac]

I am not aware of any some sort of limiters. There is no anti knock sender, no over heat engine skips a beat senders nuthin'.

Do yourself a favor and drain some coolant from the rad drain and look it over. Use a spotless clean drain pan, and clean the rad and the rec/regs so you don't drop in sand from the rec/reg fins. Use a painters paper filter with fine mesh and see what you get.