RS34 or RS36?

I've been asking myself the following question for the last six months: What makes a set of Mikuni RS36 TOO-BIG for my 82 KZ1100A-2 stock engine, considering it has an 84 bath tub head with 84 GPZ cams bolted to it?

The thought has made me crazie, considering the performance enhancement with the 36's has been nothing less than incredible.
I kept the air box as part of the intake system until one-day I decided to try out an old set of K&N PODS. Now there's no air box, since that experiment seemed to eliminate all possible restraints.

Now I suppose anyone reading this is wondering as much as I am, why try something different if it works the way it is...
It may just a simple thing, like an insatiable appetite for speed...with a tight budget. :lol:

The RS34's will be here in a couple days, and I'm wondering where to start. Thinking I'll immediately pull the bowls and check float heights, followed with verifying fuel levels with the clear-tube jigamabob.
I wonder if the smaller diameter carb flanges will fit properly into the intake manifolds, since they were stretched-out by the 36's.
Perhaps the jetting will need to be leaned-out, given the bore diameter will be smaller?

What to expect

I suspect the 34's will run cleaner in the low end.
Steve

interesting stuff.
I will put in my worthless 2 cents.
I think you will find what Sweat said but it will have a lot to do with how deftly you apply the throttle. The smaller carbs will respond better to more " hamfisted" operation than the larger.
You may need to compare based on throttle position and see if it feels stronger at particular throttle positions and if it achieves a higher rpm at particular throttle positions.
The question I am wondering is the top end….Do the 36's provide better upper mid and high rpm throttle response and HP then the 34's
How much is too much carb is going to depend on cams and porting, everything runs out of breath eventually.
Everything I have ever read is use the smallest carb that will allow max hp to be reached at the defined rpm you are trying to reach, That being said BIG carbs are the only way to make BIG power if all else works with them, but they do sacrifice street manners down low and tuning can be a real pain in that area, and I know that from trying :ohmy: And a street bike with no street manners gets old fast if one lives in high traffic areas.
Good luck and have fun!

The larger the carbs will have a weaker vacuum signal and thus the jetting sensitivity is greater. All sort of variables come into play which can be mind boggling, which is why I just leave my vintage bikes STOCK!

Good luck and sorry, I don't have much to add. I do know that the Suzuki GS1100 hotrod guys, big displacement 16V engines, tend to like the 36's. A 2V 1100 should be served perfectly well by those 34's.

I have RS34s on my '81 GPz1100. K&Ns, Kerker w/ comp. baffle, 83 cams, milled LTD head [9.9/1]
Mine was very sensitive on the idle circuit. 4/5 turns out w/ stock pilots or almost closed with the next size up.
I went with richer needles and Sudco was out of stock on needles at the time also.
On a side note I usually calculate CV carbs as having 85% of the comparable size slide carb.
34mm cv = 29mm slide. 34 X .85 = 28.9.


.

Beautiful replies, and I hope to be able to get more in-depth with this. Seems info on these RS Flat slide carbs is a bit mysterious, considering their popularity. As Ed suggests "All sort of variables come into play which can be mind boggling...".

My new/lightly used 34's arrived today :woohoo:, and they look really (really) good from the outside. But its the inside that counts, and I'll be going-thru later today to check em out.

Should I start with the same jets as in the 36's, to fire them up and sync?

See what's in them now. They might be set up right.
Steve

Nebr_Rex wrote: I have RS34s on my '81 GPz1100. K&Ns, Kerker w/ comp. baffle, 83 cams, milled LTD head [9.9/1]
Mine was very sensitive on the idle circuit. 4/5 turns out w/ stock pilots or almost closed with the next size up.
I went with richer needles and Sudco was out of stock on needles at the time also.
On a side note I usually calculate CV carbs as having 85% of the comparable size slide carb.
34mm cv = 29mm slide. 34 X .85 = 28.9.


.

Why the 85%?? I know CV carbs flow less, is that the standard formula? Seems like a lot, I though it was always taught 2 sizes down
34 cv's = to 32mm flats ?
But I can only parrot what I read or hear, math eludes me.... no engineer here :laugh:

JOE MKII wrote:

Nebr_Rex wrote: I have RS34s on my '81 GPz1100. K&Ns, Kerker w/ comp. baffle, 83 cams, milled LTD head [9.9/1]
Mine was very sensitive on the idle circuit. 4/5 turns out w/ stock pilots or almost closed with the next size up.
I went with richer needles and Sudco was out of stock on needles at the time also.
On a side note I usually calculate CV carbs as having 85% of the comparable size slide carb.
34mm cv = 29mm slide. 34 X .85 = 28.9.


.

Why the 85%?? I know CV carbs flow less, is that the standard formula? Seems like a lot, I though it was always taught 2 sizes down
34 cv's = to 32mm flats ?
But I can only parrot what I read or hear, math eludes me.... no engineer here :laugh:

Taught by whom?
It's a rule of thumb I go by. I compared the cross section of the ventri between various CV34,BS34 and VM series carbs.



.


.

swest wrote: See what's in them now. They might be set up right.
Steve

RS34's came with:
117.5 Pilot Fuel Jets
0.8 Pilot Air Jets
127 Main Jets
Needle raised one groove.

Changed to:
132.5 Main Jets
Lowered needle to 3rd. groove

I have yet to install them on the bike. Spent the evening checking them over good and cleaning them up.
Back to it in the morning.
_________________________


RS36's (on the bike):
117.5 Pilot Fuel Jets
0.7 Pilot Air Jets
135 Main Jets

Are the needle jet and needles the same also from the 34 to the 36's?


Nebr_Rex, I was taught that by a few old school drag guys I used to hang out with back in the late 80's, and it was reinforced by some testing in an old (cycle world??) motorcycle magazine doing air flow testing but only at wide open throttle, But I really don't know, like I said just repeating what I "leaned" .

Part throttle flow and atomization is what the good flat slides, smoothbores do better than anything, makes the signal so strong, really wakes up the motor, and the pilot circuit and the needle jet and/or starting needle taper become very critical in the jetting process.

JOE MKII wrote: Are the needle jet and needles the same also from the 34 to the 36's?


Nebr_Rex, I was taught that by a few old school drag guys I used to hang out with back in the late 80's, and it was reinforced by some testing in an old (cycle world??) motorcycle magazine doing air flow testing but only at wide open throttle, But I really don't know, like I said just repeating what I "leaned" .

Part throttle flow and atomization is what the good flat slides, smoothbores do better than anything, makes the signal so strong, really wakes up the motor, and the pilot circuit and the needle jet and/or starting needle taper become very critical in the jetting process.

Application chart from the Mikuni Owner's Manual below. Note emphasis:



Tuning information from same. Note Pilot Fuel Screw adjustment range: