bs34's have a slight miss on hard throttle

I have a 78 kz1000 with 4into1 vance and hines open exhaust pipe and pod filters. The carbs are bs34's with 140/42.5 jets. When tou slowly open throttle all the way it runs great.When you hit the throttle hard it has a very slight miss all through the rpms. my screws are turned out three turns. What is causing the miss? thanks

your fuel screws major effect is on the idle or low speed circuits the needle position controls the midrange the symptoms you lead me to believe that the needle position is too lean try raising it up a position or two if you can. that should get rid of most of your problem. if that doesn't help you will need a richer needle like what comes in the dynojet kit.

not that I know anything, but might the mains be too rich? With pods and exhaust on my 82kz1000 I have DJ138 mains, they run but are a bit too lean, so I am putting in mikuni 135's which should be perfect, I would think 2 more sizes up would be too fat...no?

The mains will not come into play until about the last 15-20 percent of the throttle opening. I have a 1150 with a .420 lift cam and a head that flows well over 110CFM and I am running STOCK (37.5) pilot jets and 142.5 mains. My screws are only 1 3/4 turns out, I am still way too rich at every level and my needles are as far down as they can go. If he has stock needles they are non adjustable. If these carbs came from anything els than a KZ1000/1100 the needles will be improper for the bike unless they were changed. Also if he is running pods than the slides will not react correctly without machining. The BS34s can be as good as 31mm smoothbores, but they require a bit of work and a bit of knowledge.

9am53 wrote:

not that I know anything, but might the mains be too rich? With pods and exhaust on my 82kz1000 I have DJ138 mains, they run but are a bit too lean, so I am putting in mikuni 135's which should be perfect, I would think 2 more sizes up would be too fat...no?

Too fat, or too thin! :laugh:
Depends on what the engine wants.

otakar wrote: The mains will not come into play until about the last 15-20 percent of the throttle opening. I have a 1150 with a .420 lift cam and a head that flows well over 110CFM and I am running STOCK (37.5) pilot jets and 142.5 mains. My screws are only 1 3/4 turns out, I am still way too rich at every level and my needles are as far down as they can go. If he has stock needles they are non adjustable. If these carbs came from anything els than a KZ1000/1100 the needles will be improper for the bike unless they were changed. Also if he is running pods than the slides will not react correctly without machining. The BS34s can be as good as 31mm smoothbores, but they require a bit of work and a bit of knowledge.

Whenever the mains come in.... the pilot fuel adds to that...

If you have an idle and midrange problem with bs34's take it up with the pilot screws first.

Don't change the main untill you have the low speed fuel screws set.

If it's too lean it will idle up and down,
hang up at high rpms (2000),
pop on deccel,
be flat and soggy on take off,
wide open throttle will not be eventful.

People that run the screws at 1 3/4 turns out?

By george for some reason they have a 140 main jet too!

And they wonder why...

Ok guys throw in a 42 pilot, hurry! HOly snikes turn in the those mix screws!

BACK up everybody! I'm one rich mofo now...

And then you have stories to tell.

LIke I'm rich everywhere...

STILL!

:laugh:

I gave up along time ago on the old sayings. Any carb I ever messed with
got more gas throughout all ranges if even if only one was changed.

And don't be messing with the dog gone needle.

Dyna jet tried that and look what happened...:woohoo:

You won't have a good midrange (enough gas) if the pilot screws are not open enough.

Leave that poor pilot jet alone. It has done nothing but wait for the screws to open.

Example: My pilot screws are at one turn and I have size 500 mains, should I shim the needle?

For sure! it can't hurt! go for it man! Your almost there!

What to do?

Go for popcorn and take video. Learn something.

Someday you might meet the great mark22 even. He might take you to a bug race!

bs34's

Darn good reason to wake in the morning....

It's mid morning at calf n aww racing,...
Larry sets in his office chair holding a giant mug of coffee, his pale complextion with ever receding hairline, and now an offer by NADS INTERNATIONAL....
The last 6 monthes have been hard, leaving him with the look of a withered turd

KEI HIN's face appears on the clear glass testical on his desk.

He's furious, demanding to know when the shipment of bs34's is due at nad's international.

Angry at Larry for the attempted hijack of bs34's turning out to be an empty dummy boat he

spews out foul language.

Larry's dog covers his eyes with his paws.

Nad's is in his penthouse sweet smoking a cuban cigar, putts another ball into the gold plated bs34's on the floor. With a gleam in his eye and a warm smile, he knows it's just a matter of time....




he stares out the window with what once was a pair of eyes that could see clearly.

the bs uprising has brought the need for armed assistance throughout the compound.

nads.com wrote:

otakar wrote: The mains will not come into play until about the last 15-20 percent of the throttle opening. I have a 1150 with a .420 lift cam and a head that flows well over 110CFM and I am running STOCK (37.5) pilot jets and 142.5 mains. My screws are only 1 3/4 turns out, I am still way too rich at every level and my needles are as far down as they can go. If he has stock needles they are non adjustable. If these carbs came from anything els than a KZ1000/1100 the needles will be improper for the bike unless they were changed. Also if he is running pods than the slides will not react correctly without machining. The BS34s can be as good as 31mm smoothbores, but they require a bit of work and a bit of knowledge.

Whenever the mains come in.... the pilot fuel adds to that...

If you have an idle and midrange problem with bs34's take it up with the pilot screws first.

Don't change the main untill you have the low speed fuel screws set.

If it's too lean it will idle up and down,
hang up at high rpms (2000),
pop on deccel,
be flat and soggy on take off,
wide open throttle will not be eventful.

People that run the screws at 1 3/4 turns out?

By george for some reason they have a 140 main jet too!

And they wonder why...

Ok guys throw in a 42 pilot, hurry! HOly snikes turn in the those mix screws!

BACK up everybody! I'm one rich mofo now...

And then you have stories to tell.

LIke I'm rich everywhere...

STILL!

:laugh:

I gave up along time ago on the old sayings. Any carb I ever messed with
got more gas throughout all ranges if even if only one was changed.

And don't be messing with the dog gone needle.

Dyna jet tried that and look what happened...:woohoo:

You won't have a good midrange (enough gas) if the pilot screws are not open enough.

Leave that poor pilot jet alone. It has done nothing but wait for the screws to open.

Example: My pilot screws are at one turn and I have size 500 mains, should I shim the needle?

For sure! it can't hurt! go for it man! Your almost there!

What to do?

Go for popcorn and take video. Learn something.

Someday you might meet the great mark22 even. He might take you to a bug race!

bs34's

Darn good reason to wake in the morning....

It's mid morning at calf n aww racing,...
Larry sets in his office chair holding a giant mug of coffee, his pale complextion with ever receding hairline, and now an offer by NADS INTERNATIONAL....
The last 6 monthes have been hard, leaving him with the look of a withered turd

KEI HIN's face appears on the clear glass testical on his desk.

He's furious, demanding to know when the shipment of bs34's is due at nad's international.

Angry at Larry for the attempted hijack of bs34's turning out to be an empty dummy boat he

spews out foul language.

Larry's dog covers his eyes with his paws.

Nad's is in his penthouse sweet smoking a cuban cigar, putts another ball into the gold plated bs34's on the floor. With a gleam in his eye and a warm smile, he knows it's just a matter of time....




he stares out the window with what once was a pair of eyes that could see clearly.

the bs uprising has brought the need for armed assistance throughout the compound.

....and the colored girls go doot da doot do do doot do do doot....