Does removing a baffle increase a lean condition?

Hey guys. I just got back from a quick spin on my 81' KZ1000. I was just taking a look at the bike, thinking of what i could do to clean things up and whatnot.. when i saw the head of a screw on the muffler portion of my Kerker 4-1. I removed the screw and the baffle slid out. After pushing the large red button on the righthand side of the handlebars, ive come to the conclusion that the baffle is not going back in But now im wondering.. My bike always kinda rumbles and pops on decel and when im downshifting to slow down. I know this means shes running a tad bit lean (spark plugs actually look normal, not bone white or anything) would removing the baffle only worsen her leanly-ness? I gotta say it sounds MEAN right now

Yes

yes and...

typically you will lose performance except at WOT. You need the back pressure in the exhaust for the engine to scavenge effectively. This results in a 'soft' response when cracking the throttle.

If you plan on carrying passengers, you better lay in a stock of ear-plugs....

This is a short explanation of the effects of backpressure and exhaust scavenging.
It uses a 'garden hose' analogy to explain the effect of de-restricting the exhaust
by removing the baffle.
www.thumpertalk.com/topic/571594-exhaust-backpressure-the-myth/


Here's the easy-to-grasp takeaway. You want the exhaust gases to exit the cylinder FAST, like NOW.
It creates a vacuum behind the exiting exhaust to best 'scavenge' (thoroughly remove exhaust gas from) the cylinder.

In the article it uses a cool garden hose analogy. Turn on your garden hose, open the water spigot to full open, and the water comes out the end of the hose slowly.

Use your finger or thumb to cover part of the end of the hose and the speed of the water jumps bigtime, the water shoots out fast (but less water comes out too).

So you'd think to get the exhaust out of the cylinder *FAST* you'd want to in effect "put your finger partially covering the end of the hose".

But the exhaust is designed to keep the exhaust exit speed FAST without limiting the *amount* of exhaust flow, a tricky balance.

By removing the baffle, that balance is upset. If you remove your thumb from the end of the hose, sure, more water comes out -- but much more slowly.

Removing the exhaust baffle means the exhaust flows more volume but less quickly and you're not 'scavenging' the cylinder as well (not removing the exhaust gas from the cylinder as well).

Have a read of the article, the garden hose analogy is from there:

www.thumpertalk.com/topic/571594-exhaust-backpressure-the-myth/

Kitten Tooth wrote: ...bike always kinda rumbles and pops on decel and when im downshifting to slow down. I know this means shes running a tad bit lean (spark plugs actually look normal, not bone white or anything)....

Would experiment by enrichening the pilot circuit, say 1/2 turn on each pilot adjustment screw.

That would be counter-clockwise on a bottom-located pilot mixture screw.
Or clockwise on a side-located pilot air screw.

Test run for effect. Should reduce or eliminate the popping on deceleration.

Good Fortune!

Consider putting the baffle back in. What sounds cool for 5 miles really becomes tiring after 100+ miles. (Ask how I know this :laugh: )

also if your running pods, dont forget to plug off the emmison ports on the head or take a piece of hose and link the two together. This will also cause pop on decel.

every bit of info these guys have given you is good, something to consider would be making your own baffles. I build custom exhaust on all my bikes and making baffles is easy, take a fender washer (roughly an inch or inch and a half smaller than the pipe)and weld a bot on it. put a nut on the bolt attached to the washer and put it between 6 and 8 inches from the end of the pipe and put a nut on the outside and adjust it by turning the washer and tightening the nuts to hold it in place. it works well for me (when i actually use them ) and helps the lean condition without always having to rejet the carbs while giving you the sound you want. hope it helps


Joe

Powerstroke_fan wrote: also if your running pods, dont forget to plug off the emmison ports on the head or take a piece of hose and link the two together. This will also cause pop on decel.

Will it? That emissions switch has been gone for god knows how long. The hose was pretty rotten and cracked that linked them to ports together on top of the valve cover. I found out when i did the valve clearances so i replaced it.

And i put the baffle back in. It sounded pretty neat but my bike was so loud it was obnoxious. And it made my right ear was singing after i shut the bike off and was in the driveway

Kitten Tooth wrote: And i put the baffle back in. It sounded pretty neat but my bike was so loud it was obnoxious. And it made my right ear was singing after i shut the bike off and was in the driveway

Amen! After a long ride on my BSA my friends would always say "Ed, you are shouting; quiet down a little." My reply was always

"I'M NOT SHOUTING, YOU GUYS ARE WHISPERING"

I didn't realize my hearing was be numbed from the exhaust noise just like the rest of me was from vibration. :laugh: :laugh: :laugh: :laugh: Ed