Losing RPM... and I want it back!

backcountryislife · Apr 24, 2013

13 XM, about 400 miles, 20ish hours. 146 with a skid set up to transfer well.

I'm starting climbs at 8k, but losing rpm, often dropping to 7700, 7600... even as low as 7500.

I adjusted clickers to 5 a few weeks back, which helped my initial rpm, on the flats, and for small pokes, but I'm still falling off badly imo.

I talked to my dealer & didn't get a lot of useful info aside from bumping to clicker 6, but everyone else around here is running 4 on the exact same setup. Also, being a 146, I should be spinning more RPM if anything due to less load on the sled.

Any ideas?

Wyorever · Apr 24, 2013

How's your belt look? Maybe give it a bath and clean your clutches?

backcountryislife · Apr 24, 2013

Wyorever said:
How's your belt look? Maybe give it a bath and clean your clutches?

Just put a new one on other one was a bit slickery, but a slippery belt should equal MORE rpm not less I'd think.

Blk88GT · Apr 24, 2013

Was the issue before or after the new belt?

How's the deflection of the new belt vs old one?

RKT · Apr 24, 2013

backcountryislife said:
13 XM, about 400 miles, 20ish hours. 146 with a skid set up to transfer well.

I'm starting climbs at 8k, but losing rpm, often dropping to 7700, 7600... even as low as 7500.

I adjusted clickers to 5 a few weeks back, which helped my initial rpm, on the flats, and for small pokes, but I'm still falling off badly imo.

I talked to my dealer & didn't get a lot of useful info aside from bumping to clicker 6, but everyone else around here is running 4 on the exact same setup. Also, being a 146, I should be spinning more RPM if anything due to less load on the sled.

Any ideas?

If you are riding the heavy and wet snow, the stock clutching will struggle a bit.. If you are riding powder and have this rpm issue, then you have something else wrong.
We are also finding that the fuel compensation at the higher temps are a bit aggressive (ie too lean) Nothing crazy, but over compensating a tad...

winter brew · Apr 24, 2013

First clean the sheaves, blow out the primary and secondary, make sure you don't have a broken secondary roller....make sure track and chain aren't too tight or too loose.
Then try a different belt....have seen some belts act goofy after several hundred miles of abuse and a fresh (broken in) belt brings back the RPM.
Are the temps outside dramatically warmer? Snow heavier? Any other changes to the sled like a silencer or clutch tower brace?

snengineer · Apr 24, 2013

Do what winterbrew said. If still a prob then take out a little pin weight, do whatever you have to to be running clicker 2-3 in most cases, 4 in extreme altitude or snow condtions. These etecs like 7900 max, other motors like 200-300 more for a max. More then likely it needs a good cleaning, that's always good for 200 rpm:face-icon-small-coo

*clutch cleaning is a religion all by itself, search it on snowest you will see.

....

backcountryislife · Apr 24, 2013

Strange, folks say 7900, but every dyno I've seen says 8000.

This has been in deep, SLIGHTLY wetter snow (keep in mind, this is 11-12k, so my slightly wet is still pretty light)... with both belts.

Only mod is a riser... and the windshield has been removed which adds about 4.75 HP in itself.

I'll do some housekeeping though... never hurts.

This has been on a 10 degree day, and on a 30-35 degree day as well... so temp doesn't seem to be a factor, though the loss is a little less on the colder day, where the snow would have been a bit lighter. I'd say I was at 7700-7750 with clickers on 4 that day, with less loss as the pull got longer.

I hit a chute that day and right as I turned out I saw 7730... down 170 from ideal, taking a quick look at a topo, where I turned out was about 11,700.

It is spring, so if that's just the norm for these sleds when it gets a bit warmer, not a big deal. I've been on a boosted shorty so long I'm just not used to losing RPM.

Could this be a matter of me just not loading the motor enough with the shorter track & higher clicker #?

backcountryislife · Apr 24, 2013

a few I've been looking at

I have yet to find a single dyno or piece of actual data that points to 7900 as the peak on this motor.

scottbilt95 · Apr 24, 2013

xm clutching

let's start with some basics (you may already know all of this. if you do, i'm not trying to insult your intelligence as i prefer to do that when i see you in person :face-icon-small-coo:

under what circumstances would you click?

-going up significantly (1,000 feet or more) in elevation for an extended period of time (less air for combustion at altitude)
-adding more weight to your sled or yourself than usual (creating more load)
-heavier/wetter snow (creating more load; may be your problem)
-clutch springs taking a set allowing for easier/faster upshifting. this is putting too much load too fast on the engine (as new as your sled is, highly doubtful).
-engine making less power (semi-fouled plugs due to engine break-in phase?)
-track rubbing on the sides of your tunnel (maybe has stretched a bit?)

assuming your clutching was reasonably good at some earlier point, i would try eliminate as many of these possibilities and go from there. a phenomenal clutch setup should compensate (backshift) for more load without clicking. for the most part, the only time we click is when we experience over-revving. under normal conditions, we try to stay on clicker #3 or #4 so there is room for some adjustment.

if it's not something obvious like now you are rolling with a 100 pound backpack instead of your normal 50 pounder, i would either try new plugs or bring it to the dealer and have them put it on the scanner and see if it shows anything out of the ordinary. without actually riding it, i am thinking it's down a little on engine power for some reason. stock clutching is not the most efficient but most get away with it because of the ability to click. if clicking up isn't gaining you around 200 rpms consistently, i don't think the issue is load related.

btw, if you feel the problem is you are already in clicker #6 and you simply can't go any higher, i would hope your dealer would offer some assistance (based on their cluctching preferences) to get you back into to clicker #3 or #4.

backcountryislife · Apr 24, 2013

Jeff... You're gonna have to try way harder to insult MY intelligence...

The other day I was riding with 3 of the exact same sleds except for length, with the same clutching setups from the same dealer.
As you can see this was one of the wetter, 30-35 degree days... we were SOAKED by lunch.

While Dan on the left isn't that aware of his settings (perhaps why he's been through a few 1000 top ends lately :face-icon-small-ton)
Jeremy is, and if anything he's getting more load them me from the 154... They're both in clicker 4, and I'm now in #5, losing more rpm.

Clicking up gained me about 200ish in the flats, or at the bottom of the climb... but it seems I'm losing MORE rpm with it higher.

you know though Jeff... it might be that 120 lb pack I started carrying...

You missed out this weekend sucka... shoulda come, it was disgusting up high, just a friggin BLAST.

scottbilt95 · Apr 24, 2013

xm clutching

you are correct. if the 154 guy has the same clutching as yours, you should be clicked lower as you have less engine load. could be a mechanical issue in the primary but in the past, most of these caused over-revving due to binding. this was a huge problem on the 2007 xrs due to a poor quality sheave bushing. pretty easy to open up a primary for roller inspection if you have a puller and holder. if you don't, you might want to invest in them because it is a good idea to routinely inspect the rollers and also keep the clutches clean in general. we try to keep these engines between 8000 and 8100 rpms for best performance. the peak powerband may be a little wider but not much.

backcountryislife · Apr 24, 2013

Is it possible that not loading the motor ENOUGH could cause this though?

On an m1000 if you run too light it will do the same thing, opposite of what you'd think. Will this motor do that at all, or will it generally just spin up?

Btw... Jeremy has a nice downhill hip hit built on the property right now... waiting for saturday... you know that house isn't going anywhere, you should probably just come ride

scottbilt95 · Apr 24, 2013

not enough load

i hear ya on the m1000's. chased our tails on dylan's old sled figuring that one out. don't think that's the case. if it was underloaded (if that's a word) on the flats and the base of the hill, you would think going up the hill would load it enough to get back in the powerband unless it's way out of whack. easy enough to check, keep clicking down and see if the rpms start going up.

trying to get out this weekend. was seriously depressed about not getting out anywhere last weekend.

IQRIDR · Apr 24, 2013

We change a lot of sliding sheave bushings and spring cups on ETEC 800 clutches that have less than 500 miles...a lot of the clutches are so far out of balance that they are just bushing monsters. I bet if you pull your sliding half and check your bushings they are a little on the loose side..replace the spring cup ($37) and the bushing ($22) and get it balanced and I would bet dollars you will see more RPM and tighter RPM delivery in the steep and deep. The wet snow is especially tough on the clutches and the problem is more apparent in the late season.

I also highly reccomend the 160/380 primary spring

DITCHBANGER · Apr 24, 2013

you could be having rave problems,check valves...solinoids...caps could be unscrewed a few turns from tight...?

IQRIDR · Apr 24, 2013

DITCHBANGER said:
you could be having rave problems,check valves...solinoids...caps could be unscrewed a few turns from tight...?

I was just about to post that too, check the rave valve operation very closely, we see a lot of sleds with an issue there be it a torn bellow or a loose cap.

snowmobiler · Apr 25, 2013

Riding with Parking brake on will lower rpms

backcountryislife · Apr 25, 2013

snowmobiler said:
Riding with Parking brake on will lower rpms

Biler, I need you to come along with me for a ride to monitor this possibly serious situation:face-icon-small-ton

I'll check that too...

EDIT & Update on the situation...

I found that my problem was RIGHT at about... engagement, and I've got an hourglass shaped notch worn in my belts, and smoke coming from my clutches when I try to drive.

Do you think I should adjust my clickers????

tukernater · Apr 25, 2013

maybe you could trade primary with one of your buddies and see if it's better?

Losing RPM... and I want it back!

Well-known member

Well-known member

Well-known member

Westbound and down

Well-known member

Premium Member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Similar threads