PSI Big Air Carb Tuning

[bisonboy02]

I bought a set of used 46mm series 6 Big Air carbs and looking to install them on a Polaris 660 mod snowmobile motor. I have not used these carbs before, but I'm told they perform very well. I was wondering if anyone has any tuning instruction that you could email me?
I tried emailing PSI, no luck
Any help would be great.

 

[alsled]

I tried emailing PSI, no luck
Any help would be great.

46mm on a 660?,, That just seems like there will be low velocity through the carb???????????

This is not bashing, just the truth.

From my previous expeirence with big airs, and tuning.

Throw them in the garbage.

Edit, they do perform well, at 1 throttle position you tune them to, the rest will always be off.

 

[Scott]

I know people who have had fantastic luck with their big airs...and swear by them.

I also know turbotater can talk Big Airs...PM him.

Alsled is right though....seems like a big carb for a small engine.

 

[Eli]

glhperformance here on the forums may be of some help, too. I have had 7 years of good luck with the Big Airs. VERY crisp. The key is to get the right needles.

 

[bisonboy02]

It is a 660 mod motor built by Larry Rugland.

 

[alsled]

The key is to get the right needles.

That's the whole story!!!!!!!!!!!!!!!!!!!!!!

And the problem, that's why I said you can tune the carb to do 1 thing right,

I went crazy dealing with Bruce trying to get a needle to work right at low elevation. I'd tune the carb at a certain throttle position, but it wouldn't work anyplace else.

Going back to 46mm on a 660. That's just not right in my mind even for a sled at low elevation. There will be no velocity through the carb at high elevation, no throttle responce. In my mind the only thing a 46mm carb on a 660 will ever do right is run at wot, with little throttle responce.

Next problem is finding the right needles, and calling psi and getting info, well death and tax's are things you can be sure of.

 

[alsled]

It is a 660 mod motor built by Larry Rugland.

I'm not a elevation tuner, but if at the most, if you can get rack 40's on the engine I'd do that.

Personally I use 40 mm carbs at low elevation, what I would loose in throttle responce and the small gain at wot I won't think of a bigger carb on a 800 poo engine.

 

[glhperformance]

alsled, he pmd me and i said about the exact same thing you just said. 42mm max on that 660 if you are at all going to do more than wot. And the needle deal is like poking in the dark! You in todays world with trying to find the right needle from bruce is like being a bill collector for a business dealing with PSI. good luck. lol.

 

[Turbotater]

The float assemblies are just as important as the needles.
Gotta jerk the float rods out, solder the floats to the float arms, then grind em down a bit so they clear the bowl. Once this is done then you can start looking for or experimenting with having the right needles made. The float trick also eliminates the need for the big float bowls.
I also agree with the above, 46mm too big for small motor.
Good luck

 

[Scott]

The upshot is that the 660 just won't be big enough to vibrate the hell out of things to keep the floats from settling up and down the slides properly.

LOL

 

[Eli]

glhperformance here on the forums may be of some help, too. I have had 7 years of good luck with the Big Airs. VERY crisp. The key is to get the right needles.

I have the carb sheets from good ol Bruce and for 65-83mm pistons he recommends GA-144-094 thru GA-144-106. The -094 being richest on the Wfo and the -106 being the leanest on wfo.

 

[bisonboy02]

Guess I'll keep my 40's on there, as they seem to work well.
I listed the PSI carbs in the swap meet, may sell for the right price.
If not I'll keep them for something else.
Thanks for all the info guys.

 

[suitcase]

Find yourself a good machine shop and have you 40's bored. Bump them up just a bit, have had it done with great success. If I remember right we went to 42.

Just my two penny's

 

[M7BOONDOCKIN]

Find yourself a good machine shop and have you 40's bored. Bump them up just a bit, have had it done with great success. If I remember right we went to 42.

Just my two penny's

Just wondering if suitcase is still a member on here?

 

[slash]

I had 46s on a 925 and hated them WOT they were great , I tried several sets of needles . Couldn't make them work great everywhere .
My 660 with Tatersporting works great but its a EFI motor think @ 155 hp with the clutching Im using.