Popping on decel

0

02yz426f

Member

Nov 15, 2006

319

0

• Mar 5, 2007

• #1

What causes the popping on decel if the exhaust header is tight and there are no holes in the pipe? Is it something to do with jetting?

 

oldguy

Always Broken

Dec 26, 1999

9,411

0

• Mar 5, 2007

• #2

Might mean you are running a little lean. try turning the fuel screw out a litle.

 

0

02yz426f

Member

Nov 15, 2006

319

0

• Mar 5, 2007

• Thread starter
• #3

It must be really lean because I don't even need to use the hot start lever to start the bike after it is warmed up.

 

7

76GMC1500

Uhhh...

Oct 19, 2006

2,142

1

• Mar 6, 2007

• #4

Play with the air screw first, then try a new pilot jet. It is normal for a 4-stroke to pop some when coming down from high revs. It doesn't fire on every power stroke during deceleration and some unburnt fuel/air carries over in to the exhaust. When it does fire, the fuel/air in the exhaust burns and makes the pop.

 

S

Spokes574

Member

Apr 27, 2001

171

0

• Mar 9, 2007

• #5

Motocross action wrote an article about this issue.
They indicated to go up 1 size on the pilot jet.

spokes574

 

M

Matt90GT

Member

May 3, 2002

1,517

1

• Mar 9, 2007

• #6

The 426 was such a tough bike! It make you learn about the FCR carb jetting.

Every year Yamaha did a lot of changes to the bike. Learning curve for sure.

Popping on decel usually indicates an air leak or lean pilot circuit. This could also mean the pilot jet is getting clogged up!

Be sure to do the BK mod to that carb. I ran the JD jet kit per the directions with a longer fuel screw and the bike ran great!

 

SFO

LIFETIME SPONSOR

Feb 16, 2001

2,001

1

• Mar 9, 2007

• #7

what is the jetting now?
any other mods?

 

0

02yz426f

Member

Nov 15, 2006

319

0

• Mar 10, 2007

• Thread starter
• #8

Stock jetting, but I put a new pipe on it.