Very hot exhaust on Ktm 300

[Wesman07]

Hi,

I just put a 2018 aero 120 on my 07 ktm 300 xcw. The engine never over heated but the exhaust pipe got extremely hot… enough for the silencer to boil snow. I’ve never ridden a snow bike before so it’s hard to explain what’s not normal. It felt like trying to keep a 125 on the pipe… is that normal?

The motor was just rebuilt and is still healthy. Jetting was set by the book and I errored one step richer then the condition and altitude. Plug does not seem too rich or too lean to me. Any ideas?

 

[portgrinder]

That’s normal. You can work a bike way harder on snow than dirt so the pipe will look like that. Silencer prob got that hot because it cooked 10 years of goo out of it.

If you did a proper plug chop those are still really rich. Extra fuel can turn your pipe/muffler hot faster. The extra fuel burns in the pipe.

 

[Wesman07]

That all makes perfect sense. I think it was running on the fat side as it was having a hard time coming on the pipe without really winding it up. That packing was old and saturated too.

Will the power valve timing affect pipe temps? Im wondering if its opening too early and contributing to the problem.

 

[eric82930]

That plug looks way rich. The 300s won't rev when they are to rich. What altitude are you? I ran a 150 at 7k. If yours is a w they come pretty tame/lame with a low comp head and a retarded cdi. You can check to see if the grey wire is plugged in to put the cdi on the high map but it still isn't as good as the sx it xc map. Also check to make sure the stator plate is lined up with the advanced timing mark. Retarded timing makes the exhaust hotter.

 

[Georro]

Looks like others already addressed the plug/rich mixture. My experience running a 300 on snow for three seasons is that you have to really ride the upper rpm’s to hang with the 450’s. Run the red power valve spring about a turn or two in from flush and it gets up on the pipe a lot quicker and doesn’t bog nearly as much.

Running the bike that hard made me concerned about longevity of my summer trail bike so I upgraded to a 450 XC-F two years ago. As for pipe temps on the 300, I actually lit my carbon fiber pipe guard on fire twice. After that I put one of those aluminum guards under the carbon one to give it more stand-off distance and air flow.

 

[Wesman07]

The current main is a 165 and I'm riding 4-6,000 feet. The book calls for a 163. The plug was not new nor did I do a plug chop test.

 

[GlennRMK]

You want the red spring with the adjuster flush on the PV.

Pipe looks normal to me for snowbiking and running it hard.

Riding a 300 on snow is like riding a 125 on the track. You gotta keep it wound up!

 

[CB_Rob]

That’s normal. You can work a bike way harder on snow than dirt so the pipe will look like that. Silencer prob got that hot because it cooked 10 years of goo out of it.

If you did a proper plug chop those are still really rich. Extra fuel can turn your pipe/muffler hot faster. The extra fuel burns in the pipe.

What is a plug chop?

 

[portgrinder]

The only way to look at a plug properly is to hold it at the rpm/load you want for quite awhile and then kill the motor immediately. Then when you look at the plug it will tell you what was going on at that specific point.

Starting with a new plug helps so you can see better wtf is happening