Consequences of not clutching for altitude

Don't know about every situation but Doo's in general come jetted rich, and it's easy to check and re-jet yourself if you are at all handy with wrenches. First do a little bit of reading on jetting snowmobiles, google or search here or on Dootalk dot com about jetting, doing a throttle chop test, reading plugs, and reading piston wash. You won't need all of that to do a simple eval and re-jet but it's good to read about if you are going to look into this at all yourself. Anyway figuring out if you are at least close on your jetting is fairly simple, go for a ride and do a throttle chop test and check you plugs according to this chart,

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html .

Doing a throttle chop tet is simple, ride around a bit until your sled is good and warmed up, find some long straight run where you can pin the throttle to he bar for 1/4 mile or more (100 yards at least), make a full speed run at your speedway 2 to 3 times to flow allot of fuel/oil mix over your pistons and then make your final diagnostic run at full throttle, and I mean pin it to the bar and hold it there for as long as you have room for, now before letting off the throttle at all hit the kill button and while continuing to hold the throttle to the bar ride your sled to a stop, now pull your plugs and "read" them according to the chart above. If you have a digital camera, or a camera in your phone go e=head and take a pic of your plugs and compare it once you get home. If you are rich, start jetting down, it's probubly safe to go down in 2 jet size increments until you are close, then one size at a time until you have it dialed. If you are going to do this then it's also probably easiest to just throw a real spark plug socket and wratchet in your seat bag for a couple of rides just to make things easier on yourself and so your buddies won't get to frustrated while you fuss with your tools.

Get your jetting right first then look at the clutching the clutching.

Oh, and elevations help us help you better than locations ie, don't know where Breck is, and where in MN ?

Welcome Newbmike,

I have the answers you are looking for...I live in Colorado, have two 07 800r's that are pretty dialed in, and ride Breck and the surroundings areas.

1. You most likely did not hurt your engine running you MN settings in CO, no doubt you sled probably performed like crap out here, with about a 30% horsepower loss. If you think your sled felt broken since you last rode and you rode here, thats why. Truth is you were running rich, and not in the powerband due to clutching. Typically you run rich to break in a new motor, so you should be fine.

2. I jet my stock 800r at 470, you should order a set as well. My RKtek 14.6 comp head runs nice at 450.

Now for clutching.
Option 1. Your stock sled probably has 415 ramps. You can pick up a set of +1 oversize rollers to compensate for the altitude. These roller run about $70-80 and will add 2.5g to your pin weight, I ran 11g pin with these for a total of 13.5g

Option 2. (a better option) change your ramps to 417. and around a 16g pin weight. This ramp is better at altitude.

When you are out here. Don't ride alone, ride with a beacon, probe, and shovel; if you have a spare day, do avy training! Keep in mind in doesn't take more than 30 degrees to slide. I have already had one friend buried and recovered this year.

Good Luck.

newbmike said:

Thanks, that was one of the most helpfull instructive things ive read on this forum. As for the elevations MN is Minnesota and its around 800 ft and Breck is Brekenridge Co and its between 10,000 and 12,500 ft. The clutch cover says it comes stock tuned for 2000 to 8000 and says it could damge the motor if i ride above or below that range. So far ive done both. ive put about 100 miles in Mn and 50 in breck. I live in Minnesota so i almost have to get it clutched before i jet it. Could i have done any major damage to the engine?

Click to expand...

Sounds like she was running pretty rich, and flooding out. If you don't have any problems running trails in MN, then that is where I would look. I know if I don't dip in the pow every now and then on the trails I tend to overheat, and it can be difficult to start. Sounds like some 470 jets and you will be in the ballpark.

As a rule we set-up for low elevation with solid pins, and when we go west (young man?) we swap in hollow pins. This is good for the 10K+ areas.

If your riding in between (6000') you may need to git some threaded pins that you can insert various lengths of set screws into to git the desired RPM. But if you ride at 1000, and 10,000, generally solids at home and hollows on top is a good bet.

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Hey OX,

How much did it cost you to get all those lost reps back? :focus:

BCB

Ski-Kitty: Nothing monetary. Just gotta cozy up to a funny lookin' cat. :face-icon-small-coo


Mike:

Changing the jets will have the same effect on your sled at any altitude. I don't know what yours has/had, but for example, my '02 came with 520N's. It is a safe jet that will likely never be too lean. Trouble is that it is normally way too fat and drinks lotsa gas.

The DPM will adjust for temps as well as altitude changes, but it would always be the same amount fat.

When you lean it out, it will be that much leaner at any time/place/height/temp, theoretically the same amount. Now DPM has it's limits. It can only lean out so much. +40*F and 12K' I think are the numbers used, but I am not sure if those are cumulative values or how that works. ???

Either way - if the DPM doesn't doo it;s job sometime, it will most always be too fat. Never heard of one messing up and being too lean.

I believe that the stock 800 in 02 was considered safe to drop to 480's. There was also a needle change as well. But as I am not familier with the '07 I will not tell you what is safe for that. Just use my post as an understanding as to what they are telling you to doo.


DPM delete is a whole nother deal. If you delete the DPM altogether, then you will hafta jet for the altitude and temps that you generally ride in. Or rather - what you will be riding in today. And some guys will even change them mid ride if things change too much. I hate smelling like gas (when I'm playing) almost as much as I hate wrenching when I should be playing, and I would rather let the DPM doo it for me if it works.

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