decel popping

I can't seem to get rid of the popping on decel on my 79 Kz750 twin. Is this normal for the twins?
When I got the bike it came with a two into one exhaust.


Is there supposed to be something else on the end of the can? A baffle maybe or does it have one. There is a screw hole that I maked with the arrow.


Can I repack these cans? Could this be why i'm getting the popping on decel? Where can I get a baffle for it?

Thanks.



Post edited by: kzrider, at: 2006/06/03 10:24

Ummm... I didn't mean to post it twice.:blink: Stien please delete this thread.

Post edited by: cnyl, at: 2006/06/02 17:31

I deleted the dupe post/thread.

As far as your question goes, there are a number of reasons why your noisy aftermarket pipes pop / burble on decel...

1. pilot circuit too lean... could use richer pilot jet (go up one size) and/or adjust idle mix with mixture screw

2. air leak in combustion chamber... could be bad exhaust gaskets, could be cracked vacuum caps, could be bad seal on intake manifolds, could be bad orings on pilot mixture screws, could be cracked intake manifolds

The aftermarket pipes contribute in that the decel popping is louder than it would be with a stock pipe set up but the problem is either too lean or air leak which essentially is also, too lean.

Did you purchase new exhaust gaskets? Aftermarket pipes have flanges that are thinner than the stock stuff. If you just bolt up an aftermarket pipe and aren't careful the exhaust flanges will bottom out before you get any real seal on the gaskets. I've had good luck with two used exhaust gaskets.

You pays your money and takes your chance!

Bill

Thanks for the delete wiredgeorge. I will go through the bike again tomorrow and check everything you advised.
KZCSI, I'm using used gaskets. I don't hear any leaks comming from them.
I'll keep ya posted on what I find.

Thanks

Are they a bunch of small pops or a few big bangs?

I'm not sure if the twins had the air injection systems like the fours did (Steell, do they?), but the air injection systems are notorious on the fours for big backfires on deceleration, if they are malfunctioning.

loudhvx wrote:

Are they a bunch of small pops or a few big bangs?

I'm not sure if the twins had the air injection systems like the fours did (Steell, do they?), but the air injection systems are notorious on the fours for big backfires on deceleration, if they are malfunctioning.

A bunch of sporatic small loud pops. It's driving me crazy.

cnyl wrote:

A bunch of sporatic small loud pops. It's driving me crazy.

George has it spot on. You're too lean!

I can make my bike do that too, by turning the pilot screw in half a turn... The Kaw Service Manual says to screw in the pilot screws to fully seated (gently!), then back out 1 1/2 turns, then fine-tune from there.

Of course make sure your float level is to factory spec.

Also, I have those same mufflers, and yes, you are missing the baffles. Yes, that likely will have an effect on carb performance....

Biquetoast wrote:

cnyl wrote:

A bunch of sporatic small loud pops. It's driving me crazy.

George has it spot on. You're too lean!

I can make my bike do that too, by turning the pilot screw in half a turn... The Kaw Service Manual says to screw in the pilot screws to fully seated (gently!), then back out 1 1/2 turns, then fine-tune from there.

Of course make sure your float level is to factory spec.

Also, I have those same mufflers, and yes, you are missing the baffles. Yes, that likely will have an effect on carb performance....

Do you know where I can get baffles for it?

Thanks

I messed with the pilot screws and now at idle it burps and pops as well as popping on decel.:blush: