FZR400, flatslides, and Roebling

So I have these 33mm Flatslides for my FZR, and I tried to put them on (actually, successfully put them on). Worked great at WOT, but the bike bucked me to death in the corners at part throttle. Anyway, I'm clueless about how to get these things working, but want to learn. Is anyone going to be at Roebling who would be willing to help me understand what I need to do and how to get these things to work? They were on the bike last year before I bought it and they worke fine (according to Speedwerks), so I know its not the carbs themselves.

I'd even buy dinner or something from the brat-guy .

Shawn

 

Been there...the flatslides are not set up just right. I had the same problem on my old FZR400. Huge top end power, but bucking and stuttering on part throttle under load, mid corner.

We dynoed it at Speedwerks, but never quite got it right before I sold them.

I am not sure, but it could be too much fuel in the bowls...fuel level set too high. Start there.

Keep us posted!
Ed

 

You rang?

Yeah, someone help him do up his flatsides and I'll give ya a couple brats. Free, even! Just 'cause a good deed should never go unpunis, er, unrewarded!

 

Ed,

While I appreciate the pointer, I can't say I even know how to do that. I read a whole "how to tune your flatslides tutorial" I found, but I'm too inexperienced to understand half of what its talking about. I need someone who can show me what to do.

Shawn

 

33's on a 400? A little big in my opinion but what the hell. WHat state of tune is your motor in? What are the size of the main jets? What number needles are you using? And what notch are the needles set to? Give me more info and I'll try to help. But please note that carb tuning is SWAG tuning.

 

Tracee,

The 33's are what Speedwerks put on it. The guy that had the bike before me ran with them on, but since I had heard that they take a bit of tuning, I decided to have stock carbs put back on until I at least learned how to ride.

Lets see...is a 1mm over superbike motor with megacycle cams and hindle full exhaust. You really expect me to be able to give you answers to all those other questions?

Shawn

 

Yup....

Typical Carb tuning session:

Change something one way.
Did that make it better?
Nope.
Change it back the other way.
Did that help?
No, made it worse.
DoH! WTF!?!?
Ok, change this over here.
How 'bout that?
Shouldn't have, but Yeah, much better!
Go figure...

 

Ok. Shawn please ckeck main jet size. They like to be lean for part throttle applications. They are not that hard to tune. I got mine close and haven't messed with them since. I bet the mains they have in there are huge. Try something around 110 in size. And lean the needles all the way out.

 

Is MTK around here somewhere? He was always jetting his flatsides to get maximum power

Fuel level is not hard to adjust and is often overlooked when tuning carbs.
It is just a metal tab that the floats are attached to.

 

Shawn,

If you're in the Orlando area, you could put it on the dyno at Full Spectrum (Longwood). If you have your own tools and a selection of jets, you'd be able to make the changes yourself between runs. That's how I got my SV set up, but I know the owner (Dick Suarez) pretty well. I'm just guessing that he'd let you do the same.

 

One more thought... With the bike on a stand, running in neutral, if you rev it to 4000 rpm and try to hold the throttle steady - do the revs try to rise or fall?

 

Mine would always rev fine with no lean or load on the motor. When I stuck different carbs on it, it was perfect. I really think it is the pesky float hights.

 

> great at WOT, but the bike bucked me to
> death in the corners at part throttle

Your description sounds exactly how my (SpeedWerks-tuned) 400 with flatslides operates. When I explained my (your) exact "problem" to Steve Long and Brian Kcraget one race day, I was told "pussy, shaddup and ride that bitch".

Not that I have much experience, but I’ve found (and I’ve been told by the aforementioned experts...) that flatslides are much like a light-switch; if they come "on circuit" mid corner, the bike surges a bit. This can feel a lot like “bucking me to death” if you are used to a CV-type throttle response. Maybe you don’t have a problem and just need to get used to racing flatslides?

Switching back to your CVs is always an option... the few HP you pick up on a standard 1mm over 400 with flatslides gains you little ground versus the SVs anyway.

Unless you're just out there to really put a waxing on the one or two remaining Hawks

 

They shouldn't be bucking. They can be tuned so that there is no bucking at all, just like mine.

 

Bring it on beeeeeeyotch!!!

 

I use Patrick Burns' FCR Tuning Guide myself. And a barometer, digital thermometer, and electronic relative humidity gauge. And my trusty HP-48GX Scientific Calculator to crunch the numbers. And that's only to make main jet adjustments for local weather conditions. Getting them initially dialed in involves a dyno, lots of fuel, plenty of swearing, and some fresh chicken blood for good measure.

If Mr. Burns' guide is too complex as-is, I don't think my methods are going to help clear the issue. Besides, he knows WAY more about these than I do. I know just enough to know that I'd REALLY like a bike with EFI.

 

Another simple thing you might want to make sure you check before ditching the FCRs is throttle cable play.
If you have any slop in them that could cause the mid-throttle choppyness you describled to.

 

The Burns guide that Mike points out is really good. Print a copy and put it under your pillow
You'll also need to pay attention to the throtle position you are at when you are having the problem. Is it happening at 1/4, 1/2, 3/4 or WOT. These carbs are more sensitive to throtle position and not so much to engine speed.
Don't forget that these are a pumper style carb, and if you are just whacking it wide open (like you can do all day long with the CV's) it could be flooding the engine.
Another trick is to turn the idle up to 4k --- less engine braking on corner entry and you'll also eliminate the low speed circuit as a culprit.

Don

 

"Patrick Burns' FCR Tuning Guide" = http://www.factorypro.com/tech/carbkei.html

 

I just took the 33's on my 400 apart for a cleaning. It's been sitting WAAAY to long. They have 112mj & #42pilot. I raced it almost 3 seasons and never touched the jetting and ran pump gas. Different altitudes and temps never seemed to affect them. They do run a little rough between 4-8k but on track you should never be that low anyway. The key to flatslides is to be smooth. Get them in the ballpark and learn their character and I promise you'll love 'em!!! <homer>mmmmm..flatsides