jetting

[chriselmore_1]

what would be the best jets for a mikuni sbn 44 (6r7) w/ a 61x, 180 psi head, coffmans sizzla pipe, pump cone, msd enhancer, solas 13/17

 

[Roo]

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

read through this first.

 

[chriselmore_1]

it was a GREAT thread but i didnt see anything with my specs. anyone got info?

 

[WRX Dave]

I looked through there for a similar setup and couldn't find what I needed. Almost all of the Yamaha setups in there are twin carbs.

 

[jetx]

I would start with the factory pipe jetting specs for the b pipe oin the 61x motor and than adjust from there. You may have to drop the main but it will get you in the ball park.

 

[Matt_E]

I looked through there for a similar setup and couldn't find what I needed. Almost all of the Yamaha setups in there are twin carbs.

There are 22 dual carb setups in there and 12 single setups. FYI.

 

[ryan]

I would start with the factory pipe jetting specs for the b pipe oin the 61x motor and than adjust from there. You may have to drop the main but it will get you in the ball park.

what he said. should be close.

 

[chriselmore_1]

yea i saw one setup pretty close to mine but the guy had aftermarket reeds. that should make quite a bit of difference over stock reeds right? is the coffmans sizzler pipe pretty similar to the b pipe? i hear its the next best thing.

 

[ATS_Aaron]

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

read through this first.

There has to be a cleaner way to organize this information, right? How about an excel file?

Yama/Kawi Displacement Dual/Single Brand/Model Pipe Then jetting specs

Aaron

 

[Matt_E]

yea i saw one setup pretty close to mine but the guy had aftermarket reeds. that should make quite a bit of difference over stock reeds right?

Not dramatically.

is the coffmans sizzler pipe pretty similar to the b pipe? i hear its the next best thing.

Similar enough.

 

[chriselmore_1]

matt so these jetting specs would work with my set up?( in first post)
Brand =-------Mikuni
Model =-------SBN
Size =---------44
Quantity =-----1
Main Jet =-----145
Pilot Jet =-----120
Needle/Seat =- 2.0
Spring =------ 65 gram
Pilot screw = --1.25 turns
Main Screw =--2.25 turns
- - - - - -
Gas Octane = -----------------------------91
Altitude = --------------------------------SeaLevel
Main type of riding =-----------------------Freestyle
Would it pass the 10 second WOT test = ---Yes
Powerband =-----------------Smooth, bottom mid and top best of all worlds.

 

[Matt_E]

They would certainly be a good starting point.

Popoff might be a little low.

 

[orangefinger]

N/S 1.5
95 G Spring
120 Low
130-135 High

Screw low 1.25
Screw High 1

With sea level altitude most likely N/S 2.0

 

[chriselmore_1]

so what would you recomend matt? how do i change the popoff

 

[Matt_E]

I recommend that you read this first.
It should answer most of your remaining questions.

You change popoff by changing Needle & Seat, or by changing the spring weight, or by bending the float arm, or by altering the spring. There are a few ways to do this.
In your case, I'd go with different springs - AFTER you try the lower popoff first and see how it runs.

 

[chriselmore_1]

matt thanks for the link

 

[WRX Dave]

I'm the first to admit I'm a total newbie when it comes to rejetting and messing with popoff on 2-stroke carbs. The previous owner of my 61x Blaster set it up with 35cc domes, a B-pipe, and a Riva f/a. He set it up with this:

Brand =-------Mikuni
Model =-------SBN
Size =---------44
Quantity =-----1
Main Jet =-----145
Pilot Jet =-----120
Needle/Seat =- 2.3
Spring =------ 95 gram

It runs great, but I might try a 2.0 N/S with an 80 gram spring on the 61x SJ to get a similar popoff with a smaller N/S. It runs well right now with the b-pipe and stock f/a (already installed and tuned for when I got it), but with the ADA head I'm installing with 35cc domes I figure I should just redo everything so I know what's actually in there.

 

[Mark44]

Look in the tech section for how to tune carbs.

Mark44

 

[chriselmore_1]

i pulled apart a single 44 laying around and this is what it had
n/s 2.3
high 150
low 120
95 gram spring
how does that sound on my setup? (first post)

 

[Matt_E]

Popoff might be a bit low.
Try it out.