40 mm mikuni rack carbs on a '98 700

[Jay]

I'm trying to put a set of 40mm mikunis from a '01 800 xc onto my '98 700 and I need some help. The 800s have an oil pump with 4 outlets, 2 to the crank and 1 to each carb, the 700 has 3, 2 to the crank and 1 to the fuel pump, can I plug the injectors on the mikuni carbs and run the 700 setup or should I get an 800 pump and run the oil to the carbs? Question #2 the fuel pump for the 800 has 1 outlet to the rack carbs, the 700 has 2 fuel lines, 1 to each carb, should I "T" the 2 fuel lines from the 700 setup into 1 and hook that to the rack mikunis or should I get a fuel pump from an 800 and run the single line? If I run an 800 fuel pump then I would also have to get an 800 oil pump because the 700 oil pump puts the oil into the 700 fuel pump. I think if I run the '01 800 carb boots and the '01 airbox boots the rack carbs will fit, the mikunis are shorter than the kiehens but the mikuni boots should make up the difference. Have also heard that there will be interference between the steering shaft and the r.h. mikuni carb? Also in the intake throat of the mikuni carb there is I believe an air jet, its a 0.8 on the xc and a 0.9 on the rmks, any ideas what I should run for this at 5000' to 6000'? is .9 leaner or richer than .8? Has anyone out there got any info on this swap they can share? or any jetting, general carb setup tips for the mikunis on an ET770 running PSI end dump twins? Sorry about the long winded post but it would be a lot easier if someone has done this or something similar and could help me out. thanks for any help. Jay

 

[snow whiz]

carb help

hey jay the set up will work there is no interfeance with the colume. the jet set up you want to use is from a 01 700 rmk we run the flats on a couple 97 98 700 and they work real good, better than the kiehin u can t in the 2 fuel lines into one. drop the air jet to a 9. you can run the oil line to the fuel pump. cap off the oil spouts on the carb. we dont change anything else to run them on a 700 if you would like call me 406 572 3385 rick

 

[BCDan]

I did the rack on a 97 700, and the water trap line on the mag side carb did hit the steering column. I reduced the hose to zero length, it still hit every once in a while. Make sure the carbs are clamped tight so you don't dislodge them from the adapter and create a lean spot. I ran the 2001 oil pump and plugged one outlet on the fuel pump. It was a bit of a hassle to get set up, but I liked it a lot better than the Keihin carbs...

 

[Jay]

Thanks guys, appreciate the help. What did you guys use for carb boots and air box boots? Jay

 

[99rmk700]

Got em on my 99, not sure how different it is from the 98, but I went with the stock 99 700 carb boots, and the stock airbox boots, just turned the airbox boots around to gain a little extra length. This is also with a SLP gutted airbox, so I can reach inside to help seat the carbs to the box. Was going to try the newer, longer carb boots, but they are offset to the clutch side a bit.

Seems to work good so far, had to move the box ahead slightly, going to make a spacer of some sort to fit between the box and fuel tank to get rid of any "wiggle".

 

[785RMK]

I have a set on a 00 700"785". I can't remember what they came off of but just based the jetting off of the '01 700. Really wakes the sled up. used the stock carb boots on the motor and the air box. T'd the fuel line. Changed the cables. Must of plugged the oil inlet on the carbs (Don't recall).

 

[Jay]

BCDan so one fuel line from the 700 fuel pump flows enough fuel for the rack 40mm's?

 

[785RMK]

Stock fuel pump works.

 

[BCDan]

Like 785RMK said. That sled ran like a scalded dog with the stock pump.

 

[jsledder]

TTT. Looking at doing this on 2 97 motors myself.

 

[jsledder]

Just talked to a fella that's done a couple of these retro's. He said to be sure and get a stator and CDI with 14 degree timing and that these "older" ones came with 18 degree timing. He also said that Pro X carb boots will move the carbs closer to the engine to eliminate the steering post hitting the carbs. Make any sense to any of yous.?

How can I tell what CDI I have as far as timing, as well as the stator, without tearing everything apart?

 

[99rmk700]

Why would timing make a difference for a carb swap??????

 

[Jay]

Jsleddar, DANG I like your avatar. I just spent the afternoon fitting these mikunis onto my engine and here is what I have figured out. I used the carb boots from an '00/'01 800 rmk and the stock '98 700 rmk airbox boots. I cut 8.5" off the pto carb fuel line and 2.5" off the mag carb fuel line then I "T'd" the 2 lines into 1 using a 5/16 brass "T" The stock fuel lines are 1/4" but the line to the mikunis needs to be 5/16" so I just forced the 5/16 fitting into the 1/4" line. If you could find a "T" with 2 1/4" ends and 1 5/16" end so much the better. The T ends up right under the center of the carbs and I haven't fit a piece of 5/16" fuel line from the T to the carbs yet but it should be less than 12" I used my stock '98 700 airbox but I had to move the vent nipples up slightly higher on the airbox (about 1/2") so the carbs would clear them. The float bowl water traps will clear but the mag side is very close to the steering shaft. I think I will run them but if you don't want to take the chance use Arctic Cat part #6506-032 float bowl caps, they have no water trap nipples and the clearance issue is gone. You also need to cap the oil injection nipples on the intake side of the mikuni carbs, the stock 700 oil pump feeds oil to the fuel pump. Everything fits really nice IMHO and going this route you can run your stock oil pump and fuel pump. As for jetting your on your own, I'm running a ET 770 Big bore and I'm still working on that myself. If I can help let me know. Jay

 

[jsledder]

I used the carb boots from an '00/'01 800 rmk and the stock '98 700 rmk airbox boots.

This seems to be my hangup right now, the carbs I have right now are 3-1/4" apart and that's about 1/2" too much for the stock 97 boots, are those boots your using offset? I'd only like to order these once cause it takes about 3-4 days to get and I'm 90 miles from the nearest stealer, and they are no help on things like this so it's order the parts and see if they fit.

 

[Jay]

I'm using stock polaris 2001 XC 40mm rack mikunis, on the engine side they are 3 5/8" between the edges and on the airbox side they are 2 7/8" The airbox boots are stock '98 700 RMK, they dont look offset to me, they look exactly like the '00 800 boots except they are about 1/4" shorter. The '00 800 boots are 7/8" deep and the '98 700 boots are 5/8" deep. The '00 800 carb boots are about 1/4" longer than the 700 boots, same angle. I was going to use the 800 carb boots and airbox boots but that put the airbox to far back towards the gas tank and it wouldn't fit on the aluminum edge that holds the bottom of the airbox (it is a plate thats riveted to the top of the tunnel and has the front airbox holdown strap coming up through it at the front) So the 800 carb boots and the 700 airbox boots fits perfect front to back. Side to side fits perfect as well.

Edit: I have a buddys 2000 800 RMK tore down in my shop right now ( the crank snapped in half, go figure) so I have the luxury of using parts off each machine to see what fits best.

 

[jsledder]

The set I have are 38's, spose they'll work or do I need to find 40's.?