Mixture question... Is Earlfor out there?

[ToddB3]

Hello everyone,

Just a quick question, I was reading another post of someone asking advice on his bike making popping noises on deceleration, I always thought that this was a fuel rich condition? Others answered saying it was a lean condition, can anyone explain the dynamics of this? I've heard racebikes doing this and a mechanic told me he was running fuel rich so the ram air at high speed wouldnt lean the mixture. Someone please enlighten me

Thanks

[first timer]

in my opinion if it pops like a popcorn popper on decel then it is a lean condition. if it pop a little tiny bit on decel it could be a little rich, the best thing to do is check the plugs, that will tell you exactly what is going on.

-ryan

[Anonymous]

Just like first timer said, do a plug check it will tell you everything you needed to know but were afraid to ask. Yes the popping sound you heard under a lean condition when accelerating and back is exactly that. The fuel mixture is too lean to burn properly in the combustion chamber so when it enters the hot exhaust it ignites there and makes that awful popping sound. Also when you back off on the throttle the engine picks up power as the fuel mixture is enrichened at this time, just some seat of the pants tuning. For more in depth tuning procedures go to www.factorypro.com they can explain things much better than I. Best of luck.

[KEITH KRAUSE]

Like the other guys said, it's a lean condition.
The higher the rpm's are while decelerating, the more "popping" you get.
The way I understand it is this. An engine needs a correct mixture of fuel and air to run correctly. As you ride at a higher rpm, the throttle of course is at a certain open position that's supplying a correct mixture. But as soon as you close the throttle at this higher rpm, the engine's fuel supply is inadequate. The rpm's are still high but with the jet needle fully down, the engine is only receiving fuel through the pilot circuit. The engine is drawing in air through the pilot circuit and the cut-away at a higher rate because of the higher rpm. The pilot circuit is only supplying enough fuel for lower rpm's.
This lean mixture will ignite too easily in the cylinders and burn erratically.
This is the "popping".

[whodatpat]

Thank you Kieth!

[ToddB3]

Thanks guys for the clarification, I've got the carbs set to Haynes manual specs and stock airbox and exhaust but yesterday I noticed a loud ticking on the #4 header (leaking gasket) which I think is causing the popping. I guess its time for new exhaust gaskets!

Thanks again...