680 Ultra Fuel Questions??

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phoenixcattleco

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Jan 28, 2009

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• Feb 5, 2009

• #1

I've got a 680 ultra basically stock other than slp pipes and a gutted air box, can't get the sled to quite running super rich, almost all wet plugs right up to 7,000 rpm then dry to 9. Tried adjusting needles but didn't gain much, wondering what kind of jetting I should look at, running mostly 2-4,000 feet.

 

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Throttle Junkie

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Aug 21, 2001

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• Feb 5, 2009

• #2

What main jets you running? What needles?? SLP actually made needles for these as none of the Mikuni ones would work good.

 

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theultrarider

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Nov 26, 2007

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Soldotna Alaska

• Feb 5, 2009

• #3

Make sure your have the slp needles. Slp actually makes two sets of needles for those, 1 for low elevation and one for high. Even at your elevation, make sure to run the high elevation needles. I ran mine from 0-5000' Even it 0 it ran way better on the high needles. The stock needles were pig fat even on a stock sled as were the pilot jets, thus earning them the nickname of ultra shovels around here. Go down to 30 pilots and the high elevation needles and see how it runs. I forget what I ran for mains, but it was way lower than slp's jet chart. Make sure to watch your plugs and forget about the chart.

 

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allblowdup

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Nov 26, 2007

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• Feb 6, 2009

• #4

Is it a RMK. Ultra's with pipes need a few changes to run good. The instalation manual says to back the timing off to like 10 or 12 deg @ 8000 rpm. If you do this it will run like crap. It should be set at 14 deg@8000. If it is a rmk then you should put sks or short track heads on it or just take .010 out of the squish, then it will run on 91 octane without blowing up. yes the slp high alt needles seem to be the best with 30 pilots as mentioned. Also if it is a RMK it has 1.5 cuataways on the slides , they should be cut to 2.5. If you have a sks or shorttrack they are already 2.0 so they might work ok. Jetting that worked at 2000' was 370.350.370 with P6 brass (you can use the p4's but just need to careful) It will always have a lean area at 1/2 to 3/4 throttle but that is the nature of the beast. All these specs are for the low rpm pipe that run around 8400.

 

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phoenixcattleco

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Jan 28, 2009

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• Feb 6, 2009

• #5

I am running 280 main jets, as for the needles I am not sure, is there any way I can tell what they are???

 

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phoenixcattleco

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Jan 28, 2009

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• Feb 6, 2009

• #6

The pipes are high rpm pipes cause it'll run right up to 9 grand, they are slp, they have had a fair bit of repair done to them so I am looking at a set of dyno ports to put on. I am running on high octane right now and no problems with that. It's frustrating cause it just guzzles fuel like crazy and it's not leaking anywhere. Thanks for the help,

 

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phoenixcattleco

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Jan 28, 2009

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• Feb 6, 2009

• #7

I'm also running a 162 attack 20 turned around and geared down, sled's got lots of high end but it runs like crap below 6,000 rpm

 

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allblowdup

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• Feb 6, 2009

• #8

280's are way lean. To lean to melt. Is your carb vents plugged into the air box. If the pipes are the high rpm pipes thats fine but without the other changes it will still run like crap. Fuel economy comes from your midrange not the top end. your main jets will effect everything below it (slides,brass,needle,pilots) but changing the pilots or needles or brass does bery little to the top end jetting. You need to get the main jetting right first then get your part throttle stuff worked for better economy and running. I have seen guys run 280's and they did not make enough heat to melt.

 

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j.c.higgins

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Nov 26, 2007

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St. Albert, Alberta

• Feb 6, 2009

• #9

SLP still has the setup sheets for those pipes on their wesite under Technical information. Best to rip the carbs down and find out exactly what you're running for main jet, needle jet, needles, pilots. Make sure they're sychronized also. There was a fellow recently selling a set of hi-alt needles on here. PM if needing his name. Higgins.

 

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Throttle Junkie

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• Feb 6, 2009

• #10

I would say you have 380's. 280's are LEEAAAANNN. You need the SLP needles or else it will never run.

My 800 Ultra I run around 410's, SLP needles dropped all the way with P6's. UFO and 15 pilots.

 

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phoenixcattleco

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• Feb 11, 2009

• #11

Well I tore into the carbs and I've got 280 mains, yes that is 280, P4 brass, and 40 pilots. I am in the process of going to 20 pilots. The sled is running nice on the top end, a little bog on the bottom but the smaller pilots should fix that. I'm having trouble finding any aftermarket needles. I found one set but would like another for my other sled if anyone knows of some around. THanks

 

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phoenixcattleco

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Jan 28, 2009

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• Feb 11, 2009

• #12

Also needles are all the way down, waiting on slp needles to get here.

 

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allblowdup

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• Feb 11, 2009

• #13

Here is a good question for you. What clutching are you running? If I remember we were running 10al's with the stock secondary and primary springs. I have seen guys run 280's and not blow up because they are on the wrong side of the bell curve. Only difference is they didn't make any hp. 280's is what came stock in the ultras with p4's and 40 pilots. if yours is runnig right with that jetting then it is one really weird sled. ARe vent lines attached to the airbox?
Judt found the jetting specs for the SLP pipes and there recomendation is 390,370,390 for 0-3000 ft I used to run 370,350,370 and it was nice a crisp. They don't even recomend 280's at all until 9-12000 ft. Also found my 800 bb ultra dynosheet and we ran 360's without the vents plugged into the airbox at 170 hp@8500 on Splitsencond's dyno.

 

Last edited: Feb 11, 2009

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phoenixcattleco

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Jan 28, 2009

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• Feb 11, 2009

• #14

yes the vents are plugged in from the carbs. The clutching is something I am trying to figure out but don't know yet. It was set up for the sled when I bought it. I also put another thread on here cause I have another primary clutch that I want to rebuild and am trying to find some input on weights, springs, helixes and what not. The clutch I am currently running has a purple spring. My other question is why are my plugs running dark?? The only one running remotely close to a light brown is the middle cylinder. The other two are both dark. I still haven't got the slp needles so that may change alot when I get them in.

 

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Dale Hastings

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Mar 29, 2008

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• Feb 12, 2009

• #15

Carbs: 40 pilots, p8 needle jets(nozzles), Q0 below 2000 feet,3.0 cut away on slides (I ground 2.5 to match 3.0),6DH8 needles, clip in the center, 340 mains. clutching: Drive clutch 57 gram weights, square almond spring ( make sure its not in backwords or just use a spring thats about a 150 340 rate) Driven clutch team clutch red black spring,straight 36 helix button clutch silver blue spring (set in 2 hole) straight 34 helix Gear to 2.15 ratio. 3.0 pitch track 162" 2.25 power claw is sweet (used to run 2.52 pitch 2" chalenger 9 tooth extravert drivers) Retard rmk timing a little, leave sks timing alone. I ride mostly the mountains of priest lake idaho, 2500' to 6500'. nearly 15,000 miles on this set up with 2 rebuilds. Runs very well. Slp heads

 

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Dale Hastings

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Mar 29, 2008

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• Feb 12, 2009

• #16

I forgot to mention I run dyno port pipes