My exhaust make a PFFFFT !???

[vermi]

When i drive my People 4 stroke and the motor is cold, my exhaust make a PFFFT everytime i slow down!?
It's same of a backfire but no detonation, only a PFFFT.

After 5 minutes of running (when the motor is hot) he stop to make this PFFFT and everything is normal

I check the spark plug, is not lean.

What can make this when the motor is cold???

Thank'S!

[art]

 May need to worm your bike up a little longer,your choke may still be enguaged when you take off,so you may actually be a little ritch in this case.

[wordslinger]

..that would be my guess...

..my pilot jet in my oem A50 card is too big...

..(i drilled it too big during one of my experiments)..

 

..i get the same thing when i slow down..but, all the time...

[vermi]

I put back the original muffle and upjet the pilot jet #35 for the #38.
Everything is ok now!

[art]

 Hey vermi I just re read through your posts again I was thinking you might want to raise your needle jet a little bit and try the other pipe again.