91 SN Home Port 701 Tunning Help

[bassman215]

Ok I have done a bunch of searching but would still like some opinions from those more experienced in tunning than myself.

Here's my setup....

61X/61X std bore
stock reeds
Single 44 carb OP Vortex FA
Home port job using sport port new FS templates
Coffman's Sizzler pipe
Weastcoast head - unknown dome size
- I am getting 167psi on each cylinder with a cheapo AutoZone gauge
- I imagine this might get a little better as the new rings seat etc...?

Based off my searching my starting point for carb tunning is...
2.0 NS
140 High Jet
120 Low Jet
95 gr spring
Current pop measured 30psi.
I'll have to check but I think I have my low screw set at about 1 turn out and the high screw set at 2 turns out right now

I am not really good at tunning, just don't have a lot of experience with it. I am trying to learn and get better, but would prefer not too cook my engine while learning!

I have read the mikuni manual over and over so I have a basic understanding how the circuits work together.

I just have a hard time determining lean/rich.
My plugs look pretty rich right now. I will be doing a little playing with the ski today so I thought I would ask for some help getting this thing tuned in.

Just wanted to know what you guys think about my current pop off, jetting, etc... for a starting point and any recommendations you might make. Thanks for the help. This site is the stuff!

 

[Mouthfulloflake]

im running 120/145 2.0/95gr on a very similar engine ( minus porting) and its running really well.

 

[bassman215]

Mouth, I think it was one of your old posts where I came up with those spec's. I think I ordered the 140 jet by mistake, but it's what I had so I thought I would give it a shot.

How much difference does porting usually make on tunning? Would I most likely need to step up the jet a size or two?

I just have a hard time with distinguishing rich or lean conditions. Any tips there would be helpful also.

 

[Mouthfulloflake]

how much porting changes it is over my head bassman...
Im thinking it changes it ALOT, and I would assume since the idea of porting is to flow more air, you will have to jet larger than a cylinder with stock ports.

I ran the 140 for a while and it sure seemed fine, but the 145 actually gained some rpms up top, I guess it was lean with the 140

the mikuni sbn tuning manual is your best bet for determining rich or lean.

o ahead and turn those screws a bit too and take note if your moving in the right direction or not.

the hardest thing about jetting to ME, is trying to have the same varriables each time you tune and ride... temp, water, and all that stuff figures in so its hard for me at least, to have the exact same conditions duplicated EACH time I make a change, since my garage isnt 12 seconds from the water.

 

[bassman215]

I guess the cool thing is that my folks live right on the water at the lake I live at. It's at a canyon, my wife and I are on top of the canyon, and my parents on the water in the bottom. They are about a whole minute away. It's a cool little lake, www.buffalospringslake.net. I just need to wake my butt up really early in the morning while the water is nice and smooth and do some tinkering!