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98 RMK 600 jetting help

T
Nov 23, 2013
52
19
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just picked up a 98 rmk 600. guy used to ride it in colorado, brought it to Maine four years ago and ended up putting 50 miles on in those four years.

When i bought it he told me he adjusted the clutch for the altitude change but i never thought to ask if the carbs got adjusted.

I found info in the service manual about factory jetting, which i assume is for higher elevation than i will find in Maine. I havent pulled the carbs apart to see what the jetting looks like, just looking for a starting point for when we get snow.

Factory jetting is 160 mains and 45 pilots with the jet needle in the #2 position.

Now looking at the xc 600 factory jetting, 185 mains and 45 pilots with the jet needle in the #3 position. Should i just use this as a baseline to start with once snow flies and adjust accordingly? or does anybody who has more experience with this engine have a better suggestion?

Im not a professional mechanic by any means but i do understand the concept of jetting, kind of just want to know where to begin
 

Reg2view

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Feb 1, 2010
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Get a OEM jetting and clutching chart for that year/model, it will clearly state what your baseline should be by elevation. If the rest of the motor is stock, you should be golden. Different models can have different jetting specs, based on specific carbs, exhaust, etc., so just a same year/cc could be different. You want to crack the carbs, too, and verify the main, pilot, and needle, and needle position, all of them, and set the air/fuel screws, and any slides, to spec, too. Pretty easy, but, important to avoid issues. FWIW. Good luck.
 
T
Nov 23, 2013
52
19
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Thanks I must have overlooked that the first time looking in the service manual. Got a baseline all set, just waiting on the snow to fly in a few months now
 
T
Nov 23, 2013
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19
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So we got some snow and ive had a chance to try out the sled. Once warmed up the sled runs excellent, idles at about 1600 or 1700. The issue I'm having is before its warm.

Sled starts up 2nd or 3rd pull its hard to keep running for the first minute or so, most carb'd sleds ive owned will stay running by just giving half choke a few times if it sounds like its going to die, but this one i need to keep giving it throttle and it just doesn't sound right. A few times its died and then backfires when i pull the cord again.

Is it normal for this engine or do i need to adjust something?
 

retiredpop

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Jul 3, 2001
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The keihin carbs are notorious for being a bit weak on the fuel enrichment circuit. In 1999 they added a primer to aid cold starting because of that although you say yours starts in a couple of pulls. I used to start it and leave it on full choke until it started to run really rich and then to 1/2 choke after that for a while. You could turn the air screw in from recommended setting to see if that helps or go up one size on the pilot jets.
 
T
Nov 23, 2013
52
19
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Didn't get a chance to jet the pilot up as i only have one other set of pilot jets and they are lower. I did start the sled this morning and it took 8-10 pulls instead of the usual 3, once it started i kept it on full choke for about 30 seconds while continually blipping the throttle to keep it from dying.

Sled seems to be running only one cylinder at the time, and at about the 45 second mark of running sled pops a little and sounds like its running on 2 now and starts idling by itself no problem.

What would cause the sled to run on one cylinder for a minute then jump to two. It seems to do it every time from a cold start. Once warm it runs good
 
T
Nov 23, 2013
52
19
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let it sit a few hours and tried again, this time with the air box off. this confirmed running on one cylinder for a few seconds, the pto side was firing mag was not, then the mag starts firing all of a sudden.
 

retiredpop

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Are the plug caps on the wire securely and the metal part of the cap that contacts the sparkplug in good condition? I've seen a misfire when cold when the plug cap was not securely screwed into the wire.
 
Last edited:
T
Nov 23, 2013
52
19
8
Are the plug caps on the wire securely and the metal part of the cap that contacts the sparkplug in good condition? I've seen a misfire when cold when the plug cap was not securely screwed into the wire.

Earlier today i unscrewed the caps and cut a little bit off the wires and reinstalled, and made sure to screw back in tightly
 
T
Nov 23, 2013
52
19
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Went out this morning, took a plug cap off my 2016 rmk and tried it, same problem, mag side not firing, Switched plug wires and didn't change anything, mag side still not firing.
 

retiredpop

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Jul 3, 2001
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Calgary
Okay, that pretty much eliminates the CDI and plug wires. Have you ruled out the spark plug as well by putting in fresh plugs or switching them?
 
T
Nov 23, 2013
52
19
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Okay, that pretty much eliminates the CDI and plug wires. Have you ruled out the spark plug as well by putting in fresh plugs or switching them?

99% sure I've figured it out. Said screw it and pulled carbs back off, started with double checking choke plungers were adjusted correctly and found the plunger on mag side wasn't moving at all, must be a broken cable or something. Have a spare set of carbs with throttle and choke cables so put new cable on. Let the sled sit for about 3 hrs and tried it and started on both cylinders. Ill double check tomorrow after work once its nice and cold to make sure.

now on to my voltage regulator. checked and the new one is definitely defective, didn't rev it past engagement but was already reading 18 volts. and like 15 at idle. I reinstalled the old one, which was causing a dim light situation, and that one was only reading about 3 or 4 volts no matter the rpm. makes sense to why the lights were dim. Now to figure out which one to buy, heard even oem Polaris ones aren't that great. and for 70 bucks i don't really want to chance it. Heard the arctic cat 2 wire ones are way better, but is this only oem cat ones? Theres an SPI cat one on ebay right now for like $20
 

SixtySevenGT

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Mar 25, 2008
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Middleton, Idaho
Pilot Jets

Make sure the Pilot jets are very clean. If not replace them. If this sled has sat so much chances are they are plugged.

This will cause a hugh bog all thru the range.

I own 2 1998 600 XC's I drag race them in 600 stock class
 
T
Nov 23, 2013
52
19
8
Make sure the Pilot jets are very clean. If not replace them. If this sled has sat so much chances are they are plugged.

This will cause a hugh bog all thru the range.

I own 2 1998 600 XC's I drag race them in 600 stock class

Thanks, i cleaned them the best i could. It starts first or second pull now everytime since i figured out the choke issue. I also got a new voltage regulator and my light issue is all set for now.

One more question if anybody has input. The 7 digit vin number stamped on my tunnel is 3321409. Does this seem right? Everywhere ive looked says the 2nd and 3rd digit should be the year of manufacturing. But im pretty sure my sleds not a 1932.

I know im looking at the right spot, it has VIN *3321409* stamped into the tunnel
 

sno*jet

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Dec 13, 2007
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^did you check the other side? and remember if youre going by that on a sled to figure out the year, the stamp is from the year produced, so its usually the next year's model. should be a 97 in there in your case, if its a '98.
 
T
Nov 23, 2013
52
19
8
^did you check the other side? and remember if youre going by that on a sled to figure out the year, the stamp is from the year produced, so its usually the next year's model. should be a 97 in there in your case, if its a '98.

Think I figured it out. I believe the model number is the one that has the year in it. Which is on a sticker above the vin but it's mostly scratched off. No worries, I know the year and model, just making sure I was taking the correct number to the town office to register it.
 
T
Nov 23, 2013
52
19
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Just an update. Sled has been running great but I'm having one small issue. Just about every time on a cold start the sled slightly backfires once. It always starts 3rd pull and runs and idles perfectly fine.

I heard it's kinda normal with these carbs but just don't want to ruin anything. Some suggest turning fuel off after I'm done riding. And esp while trailering.

I don't believe it's a lean pop because I'm a little rich if anything at low rpm and perfect through mid and high rpm according to the plugs.
 
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