Carb question going from 38s to 44s

[tshank123]

I've searched and I can't find a post similar to this. The question is, generally speaking, all other things being equal, when going from 38s to 44s, what would you expect your jetting changes to be? I'm guessing lower popoff for starters.

thanks.

 

[tshank123]

Nobody?

I'm just asking if you would expect leaner or richer on the jets going from 38s to 44s. Just a general question.

thanks

 

[Frosty]

You'll find that there are different jetting specs for different set ups, and everyone does something a little different

here's my jetting specs:
Main Jet 120
Pilot Jet 122.5
High speed screw 1 turn out
Low speed screw 1 turn out
Needle/Seat 2.0
Spring (grams) 95
Pop off 30

My motor setup:
Ported 61x cyl. 82mm pistons
stock 62t cases
ada head - 33cc domes
lightened flywheel
MSD enhancer
b-pipe, mod chamber with team scream head pipe/exhaust mani opened up
riva reed spacer
v-force carbon reeds

 

[Matt_E]

I've searched and I can't find a post similar to this. The question is, generally speaking, all other things being equal, when going from 38s to 44s, what would you expect your jetting changes to be? I'm guessing lower popoff for starters.

thanks.

Jetting between dual 38's and dual 44's is not comparable.
Check out the carb jetting database.

 

[tshank123]

I realize that every setup is different. Put it this way, lets say you had a setup that was pretty good but you felt like you could go with bigger carbs. First time out tuning, how would you jet? Would you expect to be running leaner on the jets compared to your smaller carbs? Lower popoff?

I've checked the database. I'm not really finding anything close to mine, probably because its a stock motor. Seems like everyone on the database is running a modified motor.

thanks guys.

 

[Matt_E]

Your dual 38 jetting is NOT a starting point for the 44's.

Dual 38's typically run 30-50 psi popoff, 70-80 pilots, 135-140 mains.
Dual 44's usually run 18-25psi popoff, 110-120 pilots, 120-130 mains.

What is your motor setup?

http://www.x-h2o.com/threads/19403

 

[tshank123]

Hey Matt, thanks, thats basically the answer I was looking for. My setup right now on the 38s is close to that.

Its a limited blaster. I just bought some 44s for it and it was jetted with 120P/130M. Couldn't tell what the n/s was but the popoff was around 34 with a shiny silver spring. If I look at the chart it suggests that its 1.5 n/s. The popoff seems a little high compared to what I've seen in the database, but he was running dual stock F/As, so makes sense to me.

I guess I'll try lowering the popoff and start with the jetting thats already in there.

 

[Mark44]

why are you changing have you done some new port work?

Mark44

 

[tshank123]

Sottie Mac suggested I go with bigger carbs. Nuff said.

 

[kevbo]

Then let him tune your carbs.

 

[tshank123]

^^^Thats a good suggestion but I'd prefer to just tune on them myself with a little direction from the experts.

 

[Matt_E]

What experts? :lmao:

 

[Crab]

Then let him tune your carbs.

Let his brother tune them.......