I just bought a 2007 525 KTM EXC?

Question

It backfires when I decelerate with the clutch not engaged and coming to a stop at medium RPMS. Is this normal

Answer 1

Backfiring when decelerating is due to a lean fuel mixture.
Richen the idle mixture screw a half turn at a time until the problem is solved (counter clockwise).
Count how many turns you make in case you want to turn it back to where you started.
http://www.bikebandit.com/partsbandit/oem-parts-nav.asp
KTM - 2007 - 525 EXC - Carbuetor - #32

Answer 2

Is it sneezing through the carb? Or is it popping out the pipe?

If it's sneezing back through the carb - this is NOT normal, and can be from an air leak, really lean jetting, or incorrect timing - and should be taken to the dealer for evaulation.

If it's doing the popppppPoppppPoppppp through the pipe, it's one of two things:

The KTM uses a pumper carb - if you've got the throttle cracked open about 1/4 throttle and the engine is at low rpm, the pump is squirting fuel when the engine doesn't need it - unburnt fuel goes into the hot pipe and then ignites.

The other thing could be a leak between the engine and the headpipe - it won't damage the engine, but can cause some obnoxious sounds, and could eventually create problems. The fix is easy - tighten the exhaust flange bolts.

All four strokes will sort of make a backfire rumbling noise (kind of like a semi truck jake brake) if you are riding down a steep hill and using the engine braking to slow down - this is normal.

Answer 3

525 Ktm

Answer 4

Yep. They run pretty lean from the factory.