Small Afterfires when throttle released.

[Nathan Rubin]

I have rebored my bike and changed to open exhaust pipe.
After that of course came jetting and tuning.
It rides great, no bugging and pushing real hard.
The one thing still bothering me.
When sudden closing of the throttle after 4k rpm and higher,
it always accompanies with 2 or 3 afterfires.
Loud "backh" "backh" sounds without actual vapor ignition at the end of the pipe.
Any clues, or is it just paranoia :bang: ?

 

[QKENUF4U]

so you took the baffle out of the exhaust can ? if so then just put it back and you wont have the pops/bangs when you let off plus youll be able to hear when your 25yrs old. :bang:

 

[Nathan Rubin]

so you took the baffle out of the exhaust can ? if so then just put it back and you wont have the pops/bangs when you let off plus youll be able to hear when your 25yrs old. :bang:

I am sure that you ain't got the problem DUDE. :coocoo:

 

[nickyd]

sounds to me like your jetting on the main might be a tad lean. we're talking a 4 stroke here right - the rule of thumb is usually to run the fuel screw 2 turns out - see where you are with that - if you are less than 2, you might want to go leaner, if you are more than 2 you might want to bump the main up richer....

 

[QKENUF4U]

no i understand perfectly fine. youve changed the backpressure in the system and have a lean pop on decel. been here done this on all my street bikes. you need to richen the pilot jet up or play with your fuel screw like stated above by nickyd. but truthfully if your just wondering if its hurting things then the answer is NO. its just burning fuel in the pipe after you close the throttle.
if you did actually pull the baffle from the can then you will more than likely NEVER get rid of the popping by just richening up the idle circuit. you would foul plugs all day long if you richen it up that much.

 

[Nathan Rubin]

sounds to me like your jetting on the main might be a tad lean. we're talking a 4 stroke here right - the rule of thumb is usually to run the fuel screw 2 turns out - see where you are with that - if you are less than 2, you might want to go leaner, if you are more than 2 you might want to bump the main up richer....

Yeap man, that is 4-stroke.
I wonder thou, is it main or pilot?
The pilot scerew is 2 1/4 turns out.
The main needle in on the 3-rd groove.

 

[Nathan Rubin]

no i understand perfectly fine. youve changed the backpressure in the system and have a lean pop on decel. been here done this on all my street bikes. you need to richen the pilot jet up or play with your fuel screw like stated above by nickyd. but truthfully if your just wondering if its hurting things then the answer is NO. its just burning fuel in the pipe after you close the throttle.
if you did actually pull the baffle from the can then you will more than likely NEVER get rid of the popping by just richening up the idle circuit. you would foul plugs all day long if you richen it up that much.

Actually the pipe built exactly as weapon silencer.
It has no baffler spark arrester at all,so gases are flowing out almost without backpressure.
So your advice is just let the beast live and ride it, wright?

 

[nickyd]

I'd ride it and not worry..but if you do, grab a pilot and a main and try one and then the other and see if the pop goes away.

 

[Mully]

So I would guess they do not enforce any type of noise ordinance?????????????????? :|

My bikes loud so I know it will go fast, just like I know that wide tires on my car makes it go fast too. :bang:

 

[Nathan Rubin]

I'd ride it and not worry..but if you do, grab a pilot and a main and try one and then the other and see if the pop goes away.

Allrighty.