pops/backfire then cuts out
 

hi, ive noticed on my 09 660x every now and then when I throttle down to approach junctions etc that my bike pops/backfires then engine cuts out, it starts straight away again, but has done this twice today and a couple of times in the past, bike is factory standard, ive only done a few hundred miles since I bought it second hand, it was one owner from new , mileage is now 9000, full history, untouched un tampered with, previous owner never used it for last year and a halve, in mint condition for age, it passed its first MOT , changed oil, coolant, brake fluid, plug, had it on a few runs with no problems, great miles to gallon, just every now and then it does this, anyone any ideas, unfortunately I am not mechanically minded, but I have a mate who runs a motorcycle garage for repairs etc, but he is away at moment, its not that much of a hassle but done it tonight when let throttle off coming up to a sharp blind bend in built up area , so its not ideal , anyone else experience this problem? thanks for taking time to read this,

Idle speed ???

not sure

Make sure it idles as near as damn it to 1500rpm. Often the idle speed is set too low (as low as 1200 in some cases), which contributes to involuntary stalling and cutting out.

ok I shall get onto that asap, sounds like could be the answer, I defo know that the prev owner who bought it new never messed around with anything just left it way it came from factory/shop, thanks

That's often the problem, dealers often set them too low from new at PDI.

pre delivery inspection ? ok I shall get it checked asap, fingers crossed that will be the answer

As it stood for a while I would also add some STP to the fuel to clean out the injectors and stuff. Good luck!!!

What I believe happens is Yamaha check the bikes as the leave the factory and set the roughly set the idle, roughly being all you can do on a brand new "tight" engine. They then arrive at the dealers, who assemble the bike and should check it again prior to delivery, but again with a tight motor and after a usually very short ride (not ideal). As the engine loosens the idle settles and more often than not the dealer doesn't check and adjust idle properly at services thereafter - don't get the engine warm enough, don't ride it far enough, maybe they can't be bothered to enter diag screen, or probably they just simply check that it idles on the stand with out stalling.

Anyhow here's a thread which explains how to get the rev counter up on the dash and how to adjust the idle...

http://www.xt660.com/showthread.php?t=801

Give it a good thrashing check idle speed after.Get a fuel device so you can give more fuel.It will thank you for it.:blob8: