[Vandever]

For starters it's a 2001 honda 400ex. I have a crack on my exhaust headers right next to flange. Is it possible to weld it while on the atv? Picture posted with thread. The pipe has been welded as one piece all the way through(not 2 pieces with there being a slip on) so getting it

off well be a challenge.

 

[SamUK]

Remove battery terminals before you do anything!

I'd tack (spot weld) in situe then remove the exhaust to fully weld. If it's cracked there's a reason, loose eachaust, over heating... Look into the reason before it causes further issues

 

[Vandever]

Before I got the Honda it had the big gun exhaust installed and who ever put it on didn't jet the carb. It had a few rides before it got jeted properly. Idk if that could make run hot to do that.

 

[SamUK]

Yep, an aftermarket exhaust could cause the motor to run hot for sure as it alters back pressure dramatically.

 

[Nhpatriot]

Looks like an issue with movement to me. motor mounts or the one piece pipe doesn't allow for expansion?
I would think too hot would burn a hole at the elbow.

 

[henrywilson]

Temperature will be a problem, it can result in unpleasant surprises, but I think you can weld it while on the atv, you just need to be careful. Make sure to remove all the rests of oil, to avoid some random ignitions. I would recommend you to have a fire extinguisher at hand for exceptional situations. Also don't forget to protect yourself with the necessary equipment, a good welding apron is must have for safety. Here is a list of reviews of the 10 best 10 Best Welding Apron Reviews 2020 - Beginner’s Guide and you can choose one for yourself if you don't have yet.