Altitude tune factory pipe 08+ SJ

[Hookah_b]

All,

Just moved from Phoenix to Denver. Engine is stock with Blowsion Tornado air filters, its an 08+... only handling mods. Has the t-handle adjusters as well. Ripped in AZ. Rode once in CO and could feel the cylinders getting loaded up in stock form (fat on fuel, I know... had to get on water before tinkering).

FINALLY got the Factory b-pipe limited. Anyone have a recommendation of where to start? Blowsion said to keep the stock settings and bolt on b-pipe first... will probably still be fat on fuel, then adjust from there. I hate the completely blind guessing game.

Main Jet:
Low Speed Jet:
Pop-off spring:
High Speed adj:
Low Speed adj:

@JetManiac

 

[fastgtfairlane]

Start with 75p, 135m,1.5n/s. 80g spring 30-35psi with the open style flame arrestor. Start with high and low screws at 1 turn each and go from there. Should be pretty close. I'd get a 65g spring and a 2.0 n/s as well to get your pop off dialed. Might end with a 65g spring with the 1.5 or the stock 115g spring with a 2.0 n/s. Just have to play with it and see what the engine likes best

 

[Hookah_b]

Start with 75p, 135m,1.5n/s. 80g spring 30-35psi with the open style flame arrestor. Start with high and low screws at 1 turn each and go from there. Should be pretty close. I'd get a 65g spring and a 2.0 n/s as well to get your pop off dialed. Might end with a 65g spring with the 1.5 or the stock 115g spring with a 2.0 n/s. Just have to play with it and see what the engine likes best

Thank you so much. The blowsion method works if I don't have a starting point. This should be much easier to get me to having fun!!!

 

[JetManiac]

Start with 75p, 135m,1.5n/s. 80g spring 30-35psi with the open style flame arrestor. Start with high and low screws at 1 turn each and go from there. Should be pretty close. I'd get a 65g spring and a 2.0 n/s as well to get your pop off dialed. Might end with a 65g spring with the 1.5 or the stock 115g spring with a 2.0 n/s. Just have to play with it and see what the engine likes best

He is in Denver which is called the mile high city because elevation is over 5000ft. This jetting will to too large and rich at that elevation.

 

[Hookah_b]

He is in Denver which is called the mile high city because elevation is over 5000ft. This jetting will to too large and rich at that elevation.

Any recommendations from you?

I've combed through as much archives as I could on this forum. Tons of variations of engines, not many at altitude. Just looking for a better starting point than what blowsion said

 

[Hookah_b]

Use the Mikuni Slide Rule to zero in on the Jets....

View attachment 426424

This is soo huge. Thanks a ton. Takes out a bit of the guess work

 

[Hookah_b]

Use the Mikuni Slide Rule to zero in on the Jets....

View attachment 426424

Looks like a 140 main jet (5-6k ft 60 degrees).

I'm not understanding the pilot though. Can you help me understand?

I plan to apply some logic for the pipe

 

[Hookah_b]

This is soo huge. Thanks a ton. Takes out a bit of the guess work

Nevermind. I need to buy one of those. Thanks

 

[Hookah_b]

No need to change the Pilot Jets, only the Main Jets.

You can see the change in Jet Sizes by comparing the Altitude changes.

Find the Altitude in Arizona Area this Ski was rode/tuned in. Somewhere around 1000 ft.

The Altitude Delta (change) is about 8000ft - 1000ft = 7000ft

Example: For a 7000ft change, the reduction is -10, so reduce the Main Jet Sizes by 10 points.

So if your Main Jet is a #135, then install a #125 Main Jet.

Then tune from there with a Tachometer and adjusting the High Speed Screws.

But if your Temp changes from 100F to 60F then, yes, you'll need the Pocket Tuner. It gets a little more complicated if both Altitude and Temperature change substantially.

Thanks. Big help. The most I've seen on here