Exhaust popping on stock bike
 

Hello XT forum.

I have a new to me 2013 XT660X that is completely stock and has gone 7800km.

However, the exhaust is popping like crazy especially when slowing down. Is this normal or is it possible that there is something wrong? I dont remember my old KLX250 having this problem.

Thanks :)

My standard 660z pops like corn in the microwave

TADTS :BaseballHat_LNY2EG:

Blocking the AIS pipe reduced the popping on my Tenere, it's worth trying.
http://www.xt660.com/showthread.php?t=5544

Don't close the throttle completely. I think its the unburned fuel escaping.

The popping and backfiring is perfectly normal. It is (as Jaques says) unburnt fuel igniting in the exhaust when the throttle is snapped shut.

On older bikes (with carbs) like your KLX the fuel wouldn't ignite (unless you had a leaky head/downpipe gasket) as it is starved of oxygen and would just pass out into the atmosphere unnoticed. Current emission regs mean that unburnt hydrocarbons in exhaust gases are a big no no, so air is deliberately introduced to the exhaust port downstream of the exhaust valves to make sure any excess fuel is ignited and burnt off.

On the XT this is known as AIS (Air Induction System) and an ECU controlled valve opens to let air into the exhaust from the airbox to burn off excess fuel when the throttle is suddenly closed. It also opens on a cold start to clean things up as the engine runs rich, and also to speed up the warm-up process as the head, exhaust ports and system will get hotter quicker because of the fuel igniting in them.

AIS is important if you have cats fitted (stock exhaust system) as unburnt fuel quickly damages the catalyst.

If you don't like the popping effect of the AIS (and you don't have cats) then you can simply block or clamp the pipe to the AIS valve that runs from the airbox (or remove the whole system altogether). You cannot just unplug the AIS valve under the tank as its default position is 'open' and the bike will pop and bang all the time!

I blocked mine for Dyno testing (messes with the test results) but then unblocked it the other day.

Shotgun!

Sounds awesome!!!! Well at least until you get an aftermarket exhaust... My Barrett single sounded like gunshots going off...fun but a tad disconcerting!

Blocked my AIS port and removed the valve entirely.

Mat

Thanks for the feedback guys. I still have the stock exhaust with the cats, so I will have to live with the popping for now. Maybe I will go aftermarkets later but the only system I really like is the OTR 2-1 Akrapovic and its super expensive, not sure I am willing to fork out the money for it, hehe. :)

Have a read in the linked thread, as you don't have to put up with it despite still being all stock.
You have the choice of blocking the intake air from the air box or you can block the air at the port near the exhaust.
Either way you go, it matters not if you are on stock pipes or aftermarket.
Matt