SUZUKI GSXR750 Carbs Mikuni

[MAXIMAN]

Ok...well it worked!

I took particular notice to the bottom end of the power curve.

From idle out to about 2500 Zilla was a little sluggish and would surge on a couple spots of that rpm range. Once he hit 3000 or 3500 then it was like being shot out of a canno. But up to that point it wasn't perfectly right.

So I took a 3/16 machine screw and cut about 1/4 inch off it. Then I drilled a 3/64 hole through that piece of screw. That's the smallest bit I had. Then I inserted that in the vaccum hose between the boost sensor and the intake boot nipple.

WOW...big improvement. I think I'll try it again tomorrow with a smaller bit.

[79XS11F]

Originally posted by MAXIMAN


What? Why would it matter if the vacuum advance line were attached to the carb or the intake boot? Both are sensing engine vaccum. Bounce back and forth?

I just installed 36mm Mikunis from an FJ1200 on my Maxim. There is no vacuum tap on the carbs so we hooked it to a intake boot. The advance seems to work fine...but then?

because if you attach directly to the boot the vaccume is TOO much for the unit and it will just bounce on and off. The vac line at #2 carb is very much restricted as has been pointed out.
Rob

[79XS11F]

Originally posted by mro


Pressure/Vacuum stays the same, regardless of hole (orifice) size.

Making it small just dampens pulses.


mro

It has more to do with the volume of aie being moved at any given vac setting.
Rob

[mro]

you read what I typed, not what I ment

quote:
--------------------------------------------------------------------------------
Originally posted by mro


Pressure/Vacuum stays the same, regardless of hole (orifice) size.

Making it small just dampens pulses.


mro
--------------------------------------------------------------------------------
Oringinally posted by 79XS11F

It has more to do with the volume of aie being moved at any given vac setting.
Rob
__________________________________________________

Size of hole vacuum advance hose hooked to will not change Pressure/Vacuum going into head. Small hole size does dampen the pulses. I use a vac gauge to sync carbs, with out a restriction in the hose the gauge is almost unreadable as it jumps around. Steady's out nicely with restriction. Does same for advance/retard unit.


mro

[underdog57]

vacuum gage sync

Would be neat to Sync the carbs with four vacuum gages . Put the
orifice in each , might be just as easy as the plenum method ...

Bob

[Ken Talbot]

Yup, that's exactly how the mercury sync sticks work. You have a small plug in each hose with a wee drilled orifice to dampen the pulses. Then the four columns are lined up next to each other so you get an immediate visual on the balance. I can't for the life of me think why you would want to try this with four round gauges. By the time you looked at one, checked its reading, then looked over at another one to check its reading, then back to the first to see if it has changed, then back to the second, you'd need to stop for a beer. Even with the restricting orifices, the mercury columns still bob up and down a bit, and I'm assuming dial gauges would do the same.

[79XS11F]

I have 4 gauge setup and the collars at the gauges turn to restrict the air flow so the needles can be set to move smoothly. Their great gauges.
Rob

[xschop]

anxiously waiting

I hope you guys figure it out, and I hope it adds at least 15 or so horses....

[xschop]

CARB DATA

Anyone figured out some newer style carb setups with real world results?....I need an inside project ....it's nasty outside....

[pggg]

Can't give ya 'official' dyno printouts but can guarantee you'll feel the extra kick in the pants from a good set of modern CV carbs, if chasing sheer performance only, forget CV's and hook into some beasty flatslides heh-heh ask MRO about the kick from those mothers..

[xschop]

your setup

I am building a 1200cc for my project and want to know what would be the best set to get....I just got offered a set of 2001gsxr TB, But I don't want to try and fuel inject yet....

[pggg]

The stock 36mm carbs from the ZRX11- 12's are real good, fit the XS with some small tweaks, Alan from Scotland says his 36mm Gixxer carbs fitted the XS manifolds too, there's sure to be others that'll come close to the XS's 79-83-79 spacing, CV's are a bit tricky to re-size coz of the fixed butterfly shaft(can be done tho) Direct link flatslide types are relatively easy to re-space, FI's outta my league - the domain of the electronic wizards..

[AlanB]

Hi Guys,

Here are my "Slingshot" carbs fitted to my SG;



These are 36mm; later bikes apparently have 38s, which have a much bigger body and are identified by having the brass link tube on one side, and a rubber one on the other.

Final option are 40mm, they are also huge, and don't have the rubber link hose. The 38s and 40s don't fit under the XS tank.

The bad news for you guys is that- as far as I can find out- The "slingshot" suzukis sold in the USA did not have these carbs, but a more conventional CV carb.

We flogged the bike on the dyno a few times, and power went from around 70bhp to touching 95. The shop replaced a lot of '80s CVs with these, with similar results.

More details http://www.benefiscal.co.uk/forum/in...sg5964#msg5964 ; Hope some of this helps!

AlanB

[underdog57]

orifice for non stock carbs

I finally put these carbs on .
took a used pilot jet and shoved it down the vacuum line .
it seems to work ...for the vacuum advance ...

I need to jet these and get them dialed in ....
noticed the jet needle is a the top slot .
has 124 main jets .
It runs , but not right yet ...
Idle screws were 3 turns out ....
will try to get some tuning imfo , I see Sudco has an good book on this ....

I think it needs to have a bigger main jet( no guts past 7k) and the needle jet give the bawaaa sound . Lean ??
And the idle mix seems to be too far out ....black #2 and #3 plugs
Might be worn jet needles , but they all look the same .

For some reason I can sync 1 to 2 and 3 to 4 , but 2 to 3 was out beyond the screw limit . might have not had the idle speed screw
set right ??or idle mix screw set too far out ??
I need to get help from a book or something ...

will play with it wednessday when I can
Bob
Picutres and details forthcoming ....

[AlanB]

Hi Underdog,

Good job!

Keep in touch!

AlanB