Hi everyone,

Im new here and so I disnt know where to start so I just thought to post my issue here. 

 

I have a YAMAHA ENDURO 125 DT it all runs good and clean. Uphill no problem. But as soon as I start climbing down the mountain it starts choking and the exhaust starts to pop loudly. I try to give it some gas it wants to go nowhere it just chokes and you hear like a deep muffled sound. Bare in mind this only occurs when going DOWN the mountain and even after I come to a flat area. I tried everything. I cleaned the carburetor, checked the YPVS even thought to leave it open static and not automatically. Still nothing. Tried new spark plugs. Still the same issue persists. All the filters are new. 

 

Bare in mind when I leave the motor to rest for 3-4 hours and try it again it works normally without any issue UNTIL it starts doing it again after that instance I showed you above. 

Hi there",   you say mountain "  what altitude are you.  you may need to drop the needle,[ clip up]   or downjet,  ,sounds like your rich ,  what plug ? ,  a hotter plu,g may  work ,try opening the airscrew a 1/4  turn ,, to see if anythin  improves,  

I go at aprox 2000m altitude. And it happens when I come back downhill. I tried opening up the YPVS, the flap that YPVS opens in the exhaust. Still the same problem.

Thats 6000 feet,   i would drop a main jet size,  ,and open the air mixture screw,  just to see ,  what colour is the plug ,-  blackish ?

Yes the plug is black. 

Ok, your well rich",  drop the needle, [at least 2 groves,]   open the airscrew a 1/2 turn more, [ 2 turns from fully home, ] , then see what you"ve  got for colour & performance, 

mind -  dropping needle is up with the clip,