Carls 910 in IQ need help with tuning - Please

[DragonSlayer1]

Having a hard time makeing carb adjustments to get my sled running at peak performance. It has EGT's, which are running above 1100 at full throttle, so I believe the jetting is close, but my bottom end is running really rich... which screws do i adjust and how far do i turn them???
The air box covers the carbs so I have to pull everything out making it really difficult to do "on the hill" adjustments.
Sled specs... 07 600 IQ chassis 159" 2.4 track - It has twin pipes, compression is 170+, big air kit with all the vents you can get. Currently running 380-390 jets, needle jets set at position 2, trying to tune for about 7500 ft + Running 66 polaris weights in drive clutch, planning to move down to 62's
Any and all tuning and adjustment advice is welcome... thanks

 

[sled_guy]

Are those SLP twins? Do you have the richer needles in the carbs?

Describe what you mean by running rich... Does it gurgle at part throttle, does it bog, does it pop? What happens if you are sitting and an idle and wack the throttle wide open?

There are both fuel and air screws on the stock carbs, which I assume are bored? The screws with the white plastic nobs are the fuel screws. You turn them in to take fuel out, open them to put fuel in. In my experience, 1/4 turn is enough to make a difference.

380-390, assuming the richer needles, is about right, maybe a bit lean for 7500, but fine for above that.

sled_guy

 

[Scott]

Don't go by your EGTS unless you know what the plug burn and piston wash are doing at those EGTs. You should set up the tuning so the plugs and piston wash are dialed and go with whatever EGTS it says at that set-up.

What year are the carbs and needles?

On my 1155 twin with 2001 Mikuno TM40 rack carbs (bored to 41.6mm), I had my needle in the 3rd and 4th clips, depending on winter or spring season.

I always ran 430-450 jets running from 4500 to 8500 feet and I could lean it down with my variflow during higher elevation rides or warm spring riding days.

380-390...you might be a little lean there.

As for the screws...if you have more than one (fuel AND and air screw), then your carbs came out in 2002 or newer, right? Mine only had an air screw because when I close it down, it leans out my bottom end.

For yours, if you have TWO, one of the screws is on the airbox side, and one is on the reed side of your carb right?

If I'm not mistaken, the one on the airbox side is the air screw and the one on the reed side is the fuel screw.
Opening it gives it more...closing it gives it less.


Am I wrong about which is which?

 

[DragonSlayer1]

Are those SLP twins? Do you have the richer needles in the carbs?
I'm not sure if they are SLP twins, I'm not sure which needles they are either, I just picked up the sled few weeks ago.
Describe what you mean by running rich... Does it gurgle at part throttle, does it bog, does it pop? What happens if you are sitting and an idle and wack the throttle wide open?
More boggy, if i open throttle fast it loads up and takes a minute to open up.

 

[DragonSlayer1]

What year are the carbs and needles?
Its an 03 motor set up, done by carls... carbs are bored

They told me when i called carls to use around 420 jets... with the fuel screw at 1 3/4 turn and the air screw at 1/2 turn. I may have turned the wrong ones, they were way different when I went to adust them so I wasn't sure. I've changed jets, but i've never messed with the carb screws before. I've been trying to get it to run better before i focus on the burn out on my plugs, or at least make sure i know what i am doing.

 

[INDEEP]

I believe the fuel screw is the small brass one closest to the motor. Screw it all the way in and then back it out a half turn. The air screw is white plastic, closest to the air box. Screw it all the way in and then back it out 1 and 3/4 turns. 02 needle is part number J8-9DGJ03-57. Email Chris at Carl's and see which one they suggest and what jetting. I think all their stuff is based on the 03 needle. They have tons of time on that motor and will get you very close right off the bat.

 

[sled_guy]

If it was setup by Carl's it has the newer needles in it. You should check just to make sure, but they did it on all the ones I know of that they setup themselves.

The 910 will handle over rich mains just fine and run well... actually the 800 big block does the same. The numbers they gave you are what I'm running but I'm running mine in an Edge chassis.

sled_guy

 

[skippy]

I believe the fuel screw is the small brass one closest to the motor. Screw it all the way in and then back it out a half turn. The air screw is white plastic, closest to the air box. Screw it all the way in and then back it out 1 and 3/4 turns. 02 needle is part number J8-9DGJ03-57. Email Chris at Carl's and see which one they suggest and what jetting. I think all their stuff is based on the 03 needle. They have tons of time on that motor and will get you very close right off the bat.

I think you might have it backwards! The fuel screws is the white and the air is the brass...

I run 400/410 mains in my 910 IQ at 7000' plus
I have my air screw(brass) backed out 1/2 turn. I would make sure yours is a 1/2 turn out and leave it there during tuning. I would then turn your fuel screws out 1 3/4, then drive it, if it's acting fat like mine was you just start turning the fuel screw in a quarter turn at a time until it wakes up. I think I ended up around one turn out when it was all said and done. Make sure your compression is where it needs to be too or you will be chasing your tail... Them 910's need new rings and pistons about every 1500 miles or less.. I rebuilt mine last year for maintenance only and once the rings seated I couldn't believe the difference it made. Are you running a stock airbox or filters?

 

[sled_guy]

Them 910's need new rings and pistons about every 1500 miles or less.. I rebuilt mine last year for maintenance only and once the rings seated I couldn't believe the difference it made. Are you running a stock airbox or filters?

Skippy, what oil do you use in your 910?

sled_guy

 

[raptobob]

White plastic knob is fuel...small straight blade screw is air.

 

[skippy]

Skippy, what oil do you use in your 910?

sled_guy

Redline oil! The 1500 mile rebuild recommendation was coming straight from Chris at Carl's... I thought it seemed low for miles too, but took his advice and did it anyways... I would rather spend the time and money now instead of 20 miles deep in the bush. LOL

 

[sled_guy]

That's interesting... I have had my 910 for 5 years now. I ride it a lot and love it. I have put new pistons and rings in it once. I use Polaris blue oil. I ran it late this season against a fresh 910 and they were neck and neck. I had a base gasket leak this year so lifted the cylinders and the pistons and rings looked brand new so I just put it back together.

Hmmm... now you have me thinking...

sled_guy