38mm cv's on 1150

[Joe H]

Ive been playing with the jetting on my 1150 which runs 38mm cv's from a 92 gixer 750.
The carbs are very close now and it runs very well BUT I have encountered a stumble at 7500 rpm or there about that clears up at 8000 rpm.
Im running factory pro jet kit specifically made for 38's on an 1150 they use standard mikuni jets, I'm at 150 mains with the stumble but she pulled like crazy with 150's above 8000rpm.
Moving to the 145 mains the stumble goes away but it doesn't pull quite as hard above 8000 rpm (a little bit less top speed shifting into 5th and a bit less acceleration)
I asked Facroty pro and they said main air jet, change it to one .2mm smaller and run 145 or 147.5 mains.

So my question is seeing these have a power jet, has anyone tried to use a power jet circuit with a set up like this? Adding a bit of fuel at the very top RPM might help.
I don't think power jets run with pods (which I have) but has anyone tried it?
I may try it for fun but I thought if I asked first maybe I could learn something or gather some more info.

Thanks

 

[Joe H]

Well I don't think anybody here really needs this info but I thought I post it anyway.
Power jets in those carbs with my set up will not work at all according to the experts. It needs the pressure difference of the air box to atmospheric pressure to work properly, so they say, and I'm not in the mood to find out.

So I went back to 145 main jets, I'm on the lowest (leanest setting) on the needles and 32 pilots and 1 3/4 turns out on the screws.
Runs great , Very good idle and part throttle operation and very good low speed low rpm operation. Great acceleration to way past redline. Great roll ons, great steady running. Fuel mileage has improved from 28 to 34 miles per gallon, it could be more if I could contain my love for high speed operation.

So to sum it up;
1260 pistons
web 370 cams (short duration)
1mm over intake valves
epoxied intake runners (supposedly to achieve higher intake velocity, thats a whole different subject)
38mm cv carbs off gixer 750
factory pro jet kit for 38mm carbs on 1100/1150 motor
"franken freak" Mac & Hines exhaust 4 into 2 into 1 exhaust.
Dyna 2000 ignition set at 10,500 redline and #4 curve.

Like I said runs great, pulls strong. Probably could be faster with different carbs and exhaust and proper porting but over all the years and the couple of different set ups Ive tried Im pretty happy with the overall performance combo.
Would like to get it dynoed again to see how much Ive lost or gained from the last time, but no money and time maybe next spring!

 

[gearhead13]

Did you have to respace the carbs to fit the port spacing on your head?
What pods are you running?

 

[Joe H]

No re-spacing necessary, all the air cooled Gixer carbs fit, as should any Bandit carb. The standard Gs boots fit also though they are TIGHT.
The pods are K&N made for those carbs, One filter for two carbs, don't know the part # offhand.

I had 36rs smoothbores before these carbs and regret getting rid of them and often think of going back to some RS's or even some lectrons.
The CV's defiantly work better for all around riding/drivability much smoother at steady speeds and low speed thru town stuff.
I do believe I split the difference between the power of 36 rs's and the better drivability of 38mm CV's they might not produce the last bit of power but they are easier on the rider, smoothing out jerky throttle transitions, and around town they are smoother at low rpm, but those rs's are something for all out acceleration! And when tuned properly work great also.
I did a bunch of stuff besides switching carbs over time with this bike just to see if my ideas would do what I thought they would and they did, but there are most likely better ways to go for all out power and drivability.

 

[GS1150Pilot]

I'm going to be running RS36 carbs when my 1229 is done. Do you think 38s are a bit much for a stock motor?

 

[Joe H]

I'm going to be running RS36 carbs when my 1229 is done. Do you think 38s are a bit much for a stock motor?

There are guys here who could answer better than me.
It really is all about the head and the cams, IMHO, when it comes to carbs. More head work, longer duration cams, higher lift, more RMP's will want more carb.
Where do you want your power is the question.
The 36 rs I had where great carbs and I do regret letting them go, when I had them on I had 1229 kit with drop in cams, Worked great.

Long story to say the 36" are probably perfect, great carb!

At the time the talk was 2mm increase in CV's = to smoothbores. So my thinking was 38MM CV same cfm as 36mm smoothbore and better all around drivability.
Is this true???? I don't know it still makes great power on top wit the CV's and it is more drivable BUT the RS's had some serious acceleration and may have been better. They did behave badly at low rpm, You have to have a bit more wrist control with smoothbores over CV's again this is just my opinion!

 

[gearhead13]

I thought that the '92 gsxr 750 was watercooled and therefore had different carb spacing than the air/oil and air cooled models.

 

[Guest]

try lowering the needle one notch with the 150 main

 

[Guest]

I thought that the '92 gsxr 750 was watercooled and therefore had different carb spacing than the air/oil and air cooled models.

Yes the 1992 GSXR750WN is a water cooled.
The 38mm C/V slingshot carbs were on the 1990 GSXR750M and the 40mm C/V carbs were on the 1989 GSXR750R. The 1991 GSXR750M got the shim/rocker head. I think. it also had the 38mm carbs with the correct spacing but I am not sure

 

[Joe H]

try lowering the needle one notch with the 150 main

I would but I'm at the lowest needle setting now, I was told to put .2mm smaller air jets in then go to 147.5 or 150. And I might do that but its running really well now so first I need to work on the starter clutch and some electrical issues. Maybe this winter if I find time.
Im also trying to finish top a H2 750 triple which is in my main work spot right now! Too much??. But fun!

And you could be right about them being from a '90 750, Id have to check my notes I have it all written down somewhere its been along time since I put the carbs on.