2006 Apex backfires

[Bigdog39]

8,000 miles on Apex. Idle is rough, seems like to much fuel, runs great off idle, but when going over 60 mph Apex will backfire when you let off the throttle and idle down towards 15 mph it will let out loud backfire. I am afraid my muffler will blow out. Seems like unburned fuel is building up in exhaust followed by explosion. Any ideas? Works fine as long as you do not let off throttle for extended period of time coming down from higher speed.

 

[actionjack]

exhaust donusts

 

[thor452]

exhaust donusts

X5

 

[Bigdog39]

Donuts replaced 1000 miles ago.

 

[thor452]

try to stop the motor wit two tennis balls and see if it shuts off like you hit the kill switch then they are fine and you need to look further if it still runs or sputters there is a problem in the exhaust.

 

[theCATman]

Ever change the sparkplugs?

Yea, we have 4 strokes, but they still wear out.

Also, try a can of Seafoam. Could be a dirty injector that's hanging open slightly, or a lazy spray pattern.

 

[Bigdog39]

Called dealer. Probably has sticking valve and valves out of adjustment. I will have valve train adjusted before I blow out muffler.

 

[Bigdog39]

Called dealer. Probably has sticking valve and valves out of adjustment. I will have valve train adjusted before I blow out muffler.

 

[theCATman]

Seriously!??

You're gonna take it to a dealer for BIG $$$ before trying two cheap simple fixes?

Wow....

 

[Bigdog39]

Tried sea foam. Did not help. I will have dealer adjust valves on Wednesday. Mechanic is pretty sharp, has worked on Yamaha's for 15 years. I will post the results of valve adjustment Wednesday evening.

 

[marq]

Donuts replaced 1000 miles ago.

It is possible for the donuts to go bad within 1000 miles. Not the most frequent thing, but I've seen it before.

 

[theCATman]

Tried sea foam. Did not help. I will have dealer adjust valves on Wednesday. Mechanic is pretty sharp, has worked on Yamaha's for 15 years. I will post the results of valve adjustment Wednesday evening.

OK, fair enough there.

Are the sparkplugs original? I'd try that first, but it's your money.

 

[actionjack]

I'm not qualified to refute a certified Yamaha mechanic but it is possible if not likely that somewhere in the flex pipe-donut-flange-header-silencer chain there is a leak even if you changed the donuts 1000 miles ago. You might as well have a peek before busting in to the valve train.

 

[buddah]

Donuts replaced 1000 miles ago.

It is possible for the donuts to go bad within 1000 miles. Not the most frequent thing, but I've seen it before.

10-4.....those clamps are basically junk.........there's a thread on here somewhere about how to grind the edges of the clamps to make them fit tighter......

 

[Murse]

has the rest of the exhaust been inspected? I had my donuts done recently had to weld the back part of my exhaust pipe the stainless steel had cracked and had 2 open gouges plus the ypipes were cracked all over I replaced the Y pipes with OEM stainless ones. So DOnuts changed to copper welded exhaust and ypipes to stainless. Stall test works great now. Try all 3 of these or tell the dealer to do so. Cost me 616$ plus 100$ copper donuts.