stutter between 5k-6k?

Here is where I am. Just rebuilt my 79 KZ1000 with 1075 kit, 10.25:1 cr, home ported head with stock valves, K410 cams, degreed at 107*, valves adjusted, spark advance working properly, BS34 carbs from wiredgeorge. The bike has a brief stutter between 5k and 6k rpm when at WOT. Runs clean up to the stutter and pulls strong after it to 11k. I can crack the throttle WOT at 1500 rpm in 5th gear and it pulls strong all the way to redline except the stutter. I put an O2 sensor mixture monitor on and it is 12.5 all the way thru the rpm band. I'm stumped?

Y Y Y you sh sh sh should expect that st st stutter when b b breaking the ssss sound b b b barrier.

Just a shot in the dark here but is there any chance that you have a vapor lock or vacuum leak that is causing that fuel flow problem? I had a similar issue last year that for some reason I couldn't pinpoint.

It would be interesting to hear from some of the veteran Kz owners on their opinions.

Cheers-Colin Firth-Ontario Canada

Are you running Pod Filters? My 81 KZ1000 has pod filters and has a similar stutter, but at a higher RPM. I've heard that this can be caused when you take off the airbox and install pod filters. Supposedly the airbox is engineered to provide the optimum intake air travel length which is shortened when you install the pods. I've also heard that one solution to this is to run velocity stacks, but they have their own drawbacks. Can anybody out there confirm this?

Cheers,

Maverick

Sounds like it's running rich in that range.

I did have the same problem from 4000 to 6500rpm. The needle was a clip to high and apparently giving to much feul. I lowered it and it's now running fine. Might be your problem to.
good luck!

Forgive my ignorance, but I'm just trying to reason through this martijn... So if the clip was too high, then the needle was too low, and lowering the clip would raise the needle and give more gas making a richer mixture. Am I thinking about this backwards? :huh: If you want to lean out the mixture in the mid-range, wouldn't you want to raise the clip, thereby lowering the needle?

Post edited by: Maverick, at: 2007/06/03 23:25

Maverick wrote:

Are you running Pod Filters? My 81 KZ1000 has pod filters and has a similar stutter, but at a higher RPM. I've heard that this can be caused when you take off the airbox and install pod filters. Supposedly the airbox is engineered to provide the optimum intake air travel length which is shortened when you install the pods. I've also heard that one solution to this is to run velocity stacks, but they have their own drawbacks. Can anybody out there confirm this?

Cheers,

Maverick

I always told customers to keep their stock air box. It had a plenum to draw non turbulent air from, and supply to 4 velocity stacks. Pods end up developing the same problems as air box boots eventually and then everything went to pot when the Dyno Jet kits came out.

Maverick wrote:

Forgive my ignorance, but I'm just trying to reason through this martijn... So if the clip was too high, then the needle was too low, and lowering the clip would raise the needle and give more gas making a richer mixture. Am I thinking about this backwards? :huh: If you want to lean out the mixture in the mid-range, wouldn't you want to raise the clip, thereby lowering the needle?<br><br>Post edited by: Maverick, at: 2007/06/03 23:25

Oohps:blush:

You are right... I made a mess of it. Yes the clip was on the lowest therfore the needle in the highest position.
I lowered the needle by raising the clip:woohoo:

Thanks Maverick!!

What style of pod filters do you have. If you have the round ones try to find a set of the bigger oval ones. I have a set of 36mm flatslides on mine and had a similar problem and I changed to the biggest filter area I could get and it got rid of 90% of the problem. The rest was tuned out with needle setting.

Yeah, I'm just running the cheap EMGO round pod filters. Guess if I don't get the needle trick to work I'll start shopping for the real deal and spring for some K&N pods. Are they the only ones that make the bigger oval filters? I've also seen that K&N has some two-boot oval filters - I wonder how they would work. Here's another thought: would increasing the length from the filter to the carb intake with some sort of tube/boot help smooth out the airflow? Where's a computational fluid dynamicist when you need one? Just curious.

Cheers!

Maverick

martijn wrote:

Maverick wrote:

Forgive my ignorance, but I'm just trying to reason through this martijn... So if the clip was too high, then the needle was too low, and lowering the clip would raise the needle and give more gas making a richer mixture. Am I thinking about this backwards? :huh: If you want to lean out the mixture in the mid-range, wouldn't you want to raise the clip, thereby lowering the needle?<br><br>Post edited by: Maverick, at: 2007/06/03 23:25

Oohps:blush:

You are right... I made a mess of it. Yes the clip was on the lowest therfore the needle in the highest position.
I lowered the needle by raising the clip:woohoo:

Thanks Maverick!!

Double post. Please delete.


Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2007/06/05 00:05