Tuning for elevation changes?

Quinc

Quinc

Buy a Superjet
Location
California
Is there rule of thumb when it comes to mikunis and elevation change? I am currently tuned for 200 ft above sea level and am curious what I should do for riding 4500 - 5100 ft above sea level. At what point do i go down a jet size or is it better to keep the jet sizes the same and go up a seat or spring size to raise pop off?
 
S

shadowrider

Location
UTAH
http://www.jetsrus.com/FAQs/FAQ_rejet_elevation_and_temperature.htm

Drop the main and pilot 5 is what I found. I bought a ski from sea level and went from a 137.5 main 75 pilot to a 132.5 main to a 70 pilot and I am at 5000'. Also had to go from 95 to 115 spring. I had multiple other problems so take this with a grain of salt as I am not sure how it ran before I got it. But according to the chart I attached it also recommended dropping 5. Good luck!
 
Quinc

Quinc

Buy a Superjet
Location
California
shadowrider said:
http://www.jetsrus.com/FAQs/FAQ_rejet_elevation_and_temperature.htm

Drop the main and pilot 5 is what I found. I bought a ski from sea level and went from a 137.5 main 75 pilot to a 132.5 main to a 70 pilot and I am at 5000'. Also had to go from 95 to 115 spring. I had multiple other problems so take this with a grain of salt as I am not sure how it ran before I got it. But according to the chart I attached it also recommended dropping 5. Good luck!
Click to expand...


According to this chart I need to go down from a 170 to a 165ish on the high. Does the same go for the low? 125 to 120?

Thanks for the link! =)
 
Quinc

Quinc

Buy a Superjet
Location
California
CARBONX2 said:
Adjusting screws will be good enough
Click to expand...

Tried that but couldn't keep it from loading up after idling. Bottom end hit was gone as well. Going from 200ft to 5100ft for a family camping trip. I am going to go down one jet size and adjust from there.
 
S

shadowrider

Location
UTAH
Turning the screws won't help with that big of altitude swing. In the chart, one is for the pilot jet, one is for the main jet. (N102/221) (N100.604) But if you look at it they are both the same number. So I would drop 5 on the high and 5 on the low. Leave your screws exactly where you have them. The only thing you may need to adjust is your idle screw a bit. That way when you go back home you can change it back to where you had it and you shouldn't have to do any tuning. No offense to the sea level guys, but they just don't realize how big effect the altitude has. This should help it from loading up, but the bottom end, and topend for that matter, is going to feel weak. Welcome to the mountains!
 
NVJAY775

NVJAY775

My home away from home.
Location
Gardnerville, Nevada, United States
I'm also at 5,000' and it sucks the ponies right out your motor. It may also depend on your carbs. I can easily dial my FS 48's from here to 200' just by adjusting the screws. It might not be spot on, but it's so darned close. They take adjustments nicely. I can't remember what the reason was that Ed from Fast Carbs said, but it's important not to run your low screws more that 1 turn out. Hopefully someone can chime in on that?
 
Philip Clemmons

Philip Clemmons

Owner, P&P Performance
Location
Richmond, Va
Eds suggestions are for his mods, not everyone else's stuff. He prefers the accuracy of jetting vs inconsistent tapered screws that vary significantly among each other.
 
amitchell

amitchell

Location
Victoria BC
Not to discount your answer, but I seem to remember seeing somewhere(I know, I know) that 1 turn was equivalent to a full jet size (5pts).

However, my high and low screws have a different pitch, one is coarse the other fine. So one turn on the high does not equal the same 1 turn change on the low. I am not sure that "turns out to jet change equivalent" will hold true between the low screw/pilot jet and high screw/main jet. This info is like trying to search for a unicorn it seems.

Just tune the boat with the watcon guide and don't over think it. http://www.x-h2o.com/index.php?threads/tuning-tips-for-rookies.39846/
 
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