Aftermarket flatslides with no choke?

Have any of you old school racers had aftermarket flat slide carbs without a choke set up on an inline 4 cylinder bike?
What issues have you encountered and how did you solve them?
Cold starting...how...couple throttle turns then start? Etc?

I'm working on putting a fresh rebuilt set of Keihin 39mm FCR's on my zx7 and they don't have a choke set up machined into the carbs.

I don't have them on the bike yet...so I have no idea whether or not I will have a problem or not...just trying to get some background info first.

Any insight would be appreciated...I'm carb ignorant.

Regards,
Chad

 

Mine do not have a choke. IIRC, I would give one quick twist of throttle so the accelerator pump would dump a squirt of fuel. Then I hit the start button. I don't recall starting ever being an issue with or without the shot of twist.

One thing you should do is determine your air/fuel ratio. Dyno is a good way to go.
On mine, the "as delivered from Sudco" jetting wasn't optimal but it ran. They were rich out of the box and I went down about 12 whole main jet sizes to get closer to a good A/F ratio. It still needs tweaking around 3500rpm where it kinda stumbles, but that's also the area where my engine starts to "come onto the cam". It's a touchy area where, ideally, I would have various needles to play with along with a whole kit full of jets. I'm wasn't riding around near 3500rpm so, it's not a big deal. The main jets, however, are a big deal. I gained 16hp before I ran out of jets.
If not a dyno, a drag strip works, too...the clocks don't lie.

You'll love 'em. Makes any aftermarket "Stage kit" for vacuum carbs look like a gimmick. Don't know what you'll hafta do about the ram air if you keep the stock airbox. I'm running individual velocity stacks, unfiltered.

At the time, I didn't know about adjusting the accelerator pump for the amount of squirt. I'll be delving into that whenever I put the bike ('95 FZR1000) back into service...it's been winterized for last twenty+ years...sleeping beast.

 

Thank you fastfreddie!

That is exactly the type of information I was looking for!!!

I'll be running without the airbox...but I'll be trying individual pod filters...not open stacks as of yet.

Regards,
Chad

 

On my FZR, if a couple twists of the throttle to work the accel pump didn't get the job done I'd 'hand' choke it by partially covering the velocity stack of problem cylinders with my hand.

 

run an airbox. and if 93 up, you def need the ram air. one of the best parts of the fcr is the stacks, blue for bottom red for top end( long = bottem end) you loose that with pods. better off with no filters at all. and get the accel pump gap correct. 1.3mm iirc and yes cold start a few pumps on throttle, just like dads old buick. lol and then some nursing till it is steady.

 

It's a 1991-92 with no ram air...yet...I know the Airtech ram air conversions are available.

Regards,
Chad

 

What @fastfreddie said.

 

Mine does not have a choke or airbox, will start at the hit of the starter button with no throttle twist and idle just fine.

 

It's been a Loooong time.
But my 89 FZR1000 had them, and I don't remember ever having a start issue, none at all. I never used a choke (Calif ?) Truthfully, I honestly don't remember if I had a choke or not?
I had a full race Yoshimura duplex pipe on that thing plus the flatslide carbs,as well as a big bore kit.
I'll tell ya what..that machine had HUGE power for it's day ..w the 5 sp the midrange pull was unreal.

The power combo like mentioned above was massive between the stock carb setup..
however...

I actually got faster 1/4 mile times with the stock header, EXUP valve and rejetted carbs.... The flatslide & racepipe...was just instant violent power ..it was uncontrollable from a dragrace start .. I could never launch it anywhere as fast from a standstill vs the EXUP equipped set up. It would just stand up almost instantly
But once going..it was just a MAD machine...I miss that bike. I wish they never changed the 89/90 design.
My GSXR /SRAD pales in comparison in brute performance... That FZR a decade older would beat bikes 10-15 years newer
The carbs really woke her up and always functioned perfect

 

All this talk about these high horsepower FZR 1000's make me feel inadequate with my 100hp zx750...

Regards,
Chad

 

Those ZX750s...just sitting on a stand look like a 200 mph machines....

 

One of my 400'2 had 32's I Believe? 2 blips of the throttle,and let it idle up to temp.I did fight with temperatures.If it ran well in the morning,it ran like shit come race time,and vice/versa.It was most likely me,but I did keep notes eventually for tracks and temps.Nothing sounds better than flatslides on a 400

 

I'll refrain from disseminating the details of my "10hp short of grenading in 10 hours" build.

 

Get ahold of Vic Fasola. He's forgot more about tuning green stuff with FCR's then most people have ever known.

I can't remember the Sudco needles he told me to get for mine back in the mid 90's but I installed them after I got home from Tally and the bike never ran better. I had put a Factory kit in them and never had a chance to test before we went to tally and the bike was un-ridable. Vic walked up, told me to yank the carbs, toss the kit in the trash, install the stock stuff and order these needles and set the clips at this height. Fixed all the fuel issues instantly.

Thanks Vic!!

 

What bike and what would be easier, you yanking your carbs to get the needle # and clip position or me trying to get ahold of Vic?