SXR Dual 44 SXR jetting.

12kistlerc

12kistlerc

Location
Clearwater, FL
Custom x-2 build...need some help on where to start with jetting... i understand this can be a tough one to answer but i just need a starting point. hoping to find someone who has built something similar.

750 big pin bottom end (stock)

sxr 800 cylinders (pretty much...#24 small pin casting with sxr sleeves. casting ported to match sleeve ports)

bored out to 83mm

kawasaki "b" head (29cc)

sxr factory wet pipe

dual 44 mikuni carbs

i plan on doing whatever decking/gasket mods to get to 180-200 compression...nothing is assembled yet.

93 octane (if that matters)

95 sxi ignition. (stock)


any suggestions on where to start with jetting? didn't have much luck surfing the interweb for people who run dual 44s on their SXR 800
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
I can check my notes next week. I have dual mikuni sbn oem carbs on my x2 with a 750bp and a mix and match superjet fpp. I THINK my carb is 120 pilots and 142/147 mains with a popoff at like 20. Not sure why my rear cylinder wanted more fuel. Maybe because i was so overpropped. I never finished tuning it but i think i was pretty close. Been busy so its just been sitting. I have it written down in my notepad bjt i think those numbers are right.
 
12kistlerc

12kistlerc

Location
Clearwater, FL
kinda stupid question, but if i went off the stock sxr 40 mm dual jetting but bumped it up one or two sizes for the dual 44's, pipe, and bore would that be an okay start? or will it be totally different from the stock sxr 40's?
 
12kistlerc

12kistlerc

Location
Clearwater, FL
Vumad said:
I can check my notes next week. I have dual mikuni sbn oem carbs on my x2 with a 750bp and a mix and match superjet fpp. I THINK my carb is 120 pilots and 142/147 mains with a popoff at like 20. Not sure why my rear cylinder wanted more fuel. Maybe because i was so overpropped. I never finished tuning it but i think i was pretty close. Been busy so its just been sitting. I have it written down in my notepad bjt i think those numbers are right.
Click to expand...
dual 44's?
 
12kistlerc

12kistlerc

Location
Clearwater, FL
MTRHEAD said:
800 uses 46i's different SBN - short and two long bolts

760 motor uses 3 hole 44 sbn/s - original style SBN
Click to expand...

here are some pictures of the carbs. i got them mailed to me from a salvage yard.
i had requested dual 44s so i assumed that's what got.
Top of the throat measures 46... throttle plate measures a little less than that. They were linked together when i got them...as you can see i cleaned the one already.

carb2.jpg carb1.jpg carb3.jpg carb4.jpg carb5.jpg
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
its the holes in the carb throat that lets fuel pass into them. OEM (Yamaha) will be 3 hole. AM SBN will be 4 hole.

How are you going to connect the linkages? Planning to replace throttle plates and shafts?
 
12kistlerc

12kistlerc

Location
Clearwater, FL
Big Kahuna said:
its the holes in the carb throat that lets fuel pass into them. OEM (Yamaha) will be 3 hole. AM SBN will be 4 hole.

How are you going to connect the linkages? Planning to replace throttle plates and shafts?
Click to expand...

The stock linkage looks like it will work just fine... they were a linked pair when i got them. when i put them on my kawie manifold with the rhaas adapter plate the are spaced apart about the same as the oem yamaha mounting plate. Am i gonna run into something i need to know about? worst case ill just buy what i need...
 
12kistlerc

12kistlerc

Location
Clearwater, FL
Big Kahuna said:
ok, cannot see the contector side of the crusty carb. Please spend some time cleaning that up!!!!!!!!!!!!
Click to expand...

....nah, I think ill just clean the one and leave the other one like poop....it adds character *sarcasm

They are getting the works man...this will be show quality when done. expensive paint too.

its for watercraft superstore 2018 magazine catalog stay tuned
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
12kistlerc said:
thank you
Click to expand...

Back home with my notes. My last post was incorrect on my highs and etc. Here's what I have written down.

My X2 setup as of last running. Its been sitting a while. It was pretty close I think but the prop was too steep and I didn't want to order a new prop.

750BP, ADA head 180 psi, OEM SBN 44 mikunis with modified XL760 airbox 2 screens per carb, Frakenpipe (westcoast 650 manifold, kawi 750 FPP head pipe, SJ FPP limited chamber), custom made 2" waterbox and 2" piping out, lightened stock flywheel, stock electronics, hooker 10/16 prop, OEM pump/nozzle/cone.

Prop was too steep for my 750 but might be okay with an 800 motor. My specs will probably get you a starting point but I'm no expert so I'd suggest going a little richer and being cautious. I am just some random guy on the internet after all.

Front carb
High 1/2 turn
low 2 turns
pilot 120
main 122.5
needle 2.0
spring
popoff 18 psi

rear
high 1-1/8 turn
low 2 turns
pilot 120
main 127.5 (yes, richer than the front, I suspect related to my prop but who knows)
needle 2.0
spring
popoff 18

again, disclaimer that I could be way off base. I could never get it to where I was happy. It hit hard at about 3500 RPM but was real lazy until then. It didn't bog or stall, just real lazy, and when I got a tach it was 7200 RPM and Xmetal said I needed to let my kawi motor turn to 7800 RPM. Plugs were nice delicious marshmellow brown, but the rear plug got light when I hard the same jet as the front carb.

Hope that helps.

PS. Am willing to sell the prop. It has about 2 hours on it in a pump with a rebuilt liner. I'd like a 9/15 hooker.
 
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