Less back pressure pipe = Lean 1150?

[Carter Turk]

I was messin around with my Kerker pipe today (K-2 aluminum can). The way the can mounts to the S bend pipe is pretty hokey. It's always slipping back and the mounting bracket fits at an odd angle to the rear peg mount. So this led me to try a different Kerker pipe I had laying around.

I've already broken two of these pipes (thin gauge aluminum), so I have an old one that I cut down and used a Yosh sleeve with a FZ750 race baffle. The end cap is the same on both,
maybe an 1 1/2'' diameter.

The FZ exhaust baffle is much larger so it feels more free flowin. I rode it today and when I would come to a stop the idle would hang up a bit. No hanging with the other pipe, which led me to believe it might be running leaner. I haven't checked the plug yet and the bike accelerated flawlessly through the rev range. It even seemed smoother at small steady throttle. Any thoughts on this?

[Steve]

Yes, freer-flowing will be a bit leaner. Best to check your plugs before your accidently deposit some aluminum on them.

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[Dave8338]

I was messin around with my Kerker pipe today (K-2 aluminum can). The way the can mounts to the S bend pipe is pretty hokey. It's always slipping back and the mounting bracket fits at an odd angle to the rear peg mount. So this led me to try a different Kerker pipe I had laying around.

I've already broken two of these pipes (thin gauge aluminum), so I have an old one that I cut down and used a Yosh sleeve with a FZ750 race baffle. The end cap is the same on both,
maybe an 1 1/2'' diameter.

The FZ exhaust baffle is much larger so it feels more free flowin. I rode it today and when I would come to a stop the idle would hang up a bit. No hanging with the other pipe, which led me to believe it might be running leaner. I haven't checked the plug yet and the bike accelerated flawlessly through the rev range. It even seemed smoother at small steady throttle. Any thoughts on this?

More air out means more air in. Unless you have the fuel to match "said air out", you will be running lean.
Everything else being equal, the flow path is what counts.
If you have a measured path of, for example 15" and that is changed to 25 inches (baffeling and routing), the exit time per stroke changes, greatly.

In tuning two-stroke engines, this is the primary source of added power. YES, the two are not exactly the same, but they do sahre a common root.

[chef1366]

What are you running for carbs and jetting?

[chef1366]

Yes, freer-flowing will be a bit leaner. Best to check your plugs before your accidently deposit some aluminum on them.

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Amen to that brother!

[rapidray]

Carter, reset the mixture screws & the idle issue will go away. You will need then to see if you have to adjust the needles & mains to compensate there also. Ray.

[Carter Turk]

Chef,
I'm running 90 gsxr 1100 carbs with factory jet kit and K&N pods. Middle clip on needle, 142.5 mains, 32 pilots and floats leaned a bit to keep from fouling plugs due I believe to the 15 degree angle of the carbs on a gsxr versus flat.

[Steve]

Yes, freer-flowing will be a bit leaner. Best to check your plugs before your accidently deposit some aluminum on them.

Amen to that brother!

There's just something about being part of the "BTDT" crowd, isn't there?


I have never deposited aluminum on the plugs, but I did have a valve adjustment problem and did not realize it. It was compensated for with an adjustment to the fuel injection, but that made the mixture so rich that deposits formed on the pistons and valves. The buildup on the pistons eventually bent all six intake valves ever so slightly. Believe me, replacing valves in a Kawasaki 1300 engine is NOT cheap.

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[chef1366]

There's just something about being part of the "BTDT" crowd, isn't there?


I have never deposited aluminum on the plugs, but I did have a valve adjustment problem and did not realize it. It was compensated for with an adjustment to the fuel injection, but that made the mixture so rich that deposits formed on the pistons and valves. The buildup on the pistons eventually bent all six intake valves ever so slightly. Believe me, replacing valves in a Kawasaki 1300 engine is NOT cheap.

.

How about deposited aluminum on the valve seats?

[Steve]

How about deposited aluminum on the valve seats?

Not me. It was just a lot of carbon build-up.

Do you know someone who has deposited aluminum on the valve seats?

.

[Carter Turk]

As Ray said, the mixtures screws solved the hang up, but I first wanted clarify
the larger baffle makes a bike run leaner. This pipe is rather loud, so I might have to revert to the old one.