You guys on here know your stuff, so here it goes. I have a '05 RMK 900 159" w/1500 miles, slp pipe and can, new vForce 3 reeds and intake sockets, timbersled intake. Compression is right at 120 each side. I Ride usually 9-12k feet. The sled runs good but i think it could run better! WOT 7550 rpm, i am currently running 10-68 polaris weights, MTX Blue/Pink spring, stock setup secondary, 19/39 gearing. Seems like it needs a little bit more power for hills. Local dealers/performance shops seem to always say, "wow, a 900 that still runs", not the answers i am looking for! My questions are: 1- What should the WOT be for this beast? 2-What point do you do a top end? 3-What set up would you guys run? I have been reading the previous threads on the 900's but am stuck. Top end time or not?
Where to look next? Top end or Not?
- Thread starter krolhead
- Start date
you need more RPMs for sure.
you should be hitting around 7800 rpm...
10-70 weights are for 8000-10000ft, but 68s should still hit that rpm.
is your primary spring old? (like older then 1-2 seasons) might be sacked out spring not getting full shift out.
have you had your primary serivced lately...check buttons, weight bushings, clean clutches very good, rollers in your secondary worn out.
i would do a clutch rebuild if you havent done any of above..
also i would change your secondary setup and use the red/pink spring and 66/44.46 or close to helix.
hope that helps.
you should be hitting around 7800 rpm...
10-70 weights are for 8000-10000ft, but 68s should still hit that rpm.
is your primary spring old? (like older then 1-2 seasons) might be sacked out spring not getting full shift out.
have you had your primary serivced lately...check buttons, weight bushings, clean clutches very good, rollers in your secondary worn out.
i would do a clutch rebuild if you havent done any of above..
also i would change your secondary setup and use the red/pink spring and 66/44.46 or close to helix.
hope that helps.
I just had the clutch redone the later part of season last year. New buttons, rollers, weights, and spring. Would dirty exhaust valves steal 250-300 rpm?
Might not directly help your rpm issue, but another thing you can do is to gear down - make better use of the power you have. On the 05; 18/40 is very popular, I run 18/39 and am happy, or if you want to get a bigger chain you can do 19/42. Might help get you a little more track speed and better utilize the 111 lb ft of torque.
Last edited:
M
miller tools
Well-known member
weights
i had the same problem on my 900 with 10-68s went to 10-70s got rpms back i think the weights are a little light its something to try worked for me
i had the same problem on my 900 with 10-68s went to 10-70s got rpms back i think the weights are a little light its something to try worked for me
By "stock setup secondary" do you mean the stock helix?
That was a major problem with these sleds.
Hmmm..
The clutching has been pretty much worked out on theses sleds by trial and error.
Motor mounts, belt life and a lot of other concerns are things that will benefit from changing out the clutching/gearing
What I'm reading you have
You did not indicate the belt that you were using, but I would ONLY recommend 3211115 from Polaris as there are no aftermarket belts that come up to the std of this belt from Mitsuboshi (not misubishi).
One of the most common setups for your sled at your altitude would be
Primary spring Polaris Almond (AKA Black-3342 pn 7043342)
Primary weights for your altitude 10-68
Secondary helix 66-44/42 run in the 44 position.
Secondary Spring Red/pink 140-260 (The stock red black 140-240 will work ok for some too)
Change out the gearing to 19-42 and make sure you use good quality chaincase oil and that the chain has proper tension.
Make sure that the belt, pn 321115 has been washed with super hot water, scrub with a stiff brush on both sides (do a good job), rinse well with hot water and hang to dry.
Now... here is a detail not to be taken lightly... The belt side-clearance from the factory was not set for the width of the 3211115 belt. This must be reset and most people don't have the tools to do this with. I suggest that you send in the clutch for re-balance and clean up... this is THE primary connection from your motor to the sled make sure it is as spot-on as possible.
Once installed, the belt deflection can be set easily, take your time to do it correctly. (in your Owners manual)
New springs every season.
If you have a high mile clutch... Definately have it serviced.
The clutching system is the heart of your sled and its performance...This is the one area NOT to cut costs on.
Also, most 2005 900's that I've worked on have broken motor mounts that also affect the performance...unfortunately, you cant service these or even check them without pulling the motor...
That was a major problem with these sleds.
Hmmm..
The clutching has been pretty much worked out on theses sleds by trial and error.
Motor mounts, belt life and a lot of other concerns are things that will benefit from changing out the clutching/gearing
What I'm reading you have
You did not indicate the belt that you were using, but I would ONLY recommend 3211115 from Polaris as there are no aftermarket belts that come up to the std of this belt from Mitsuboshi (not misubishi).
One of the most common setups for your sled at your altitude would be
Primary spring Polaris Almond (AKA Black-3342 pn 7043342)
Primary weights for your altitude 10-68
Secondary helix 66-44/42 run in the 44 position.
Secondary Spring Red/pink 140-260 (The stock red black 140-240 will work ok for some too)
Change out the gearing to 19-42 and make sure you use good quality chaincase oil and that the chain has proper tension.
Make sure that the belt, pn 321115 has been washed with super hot water, scrub with a stiff brush on both sides (do a good job), rinse well with hot water and hang to dry.
Now... here is a detail not to be taken lightly... The belt side-clearance from the factory was not set for the width of the 3211115 belt. This must be reset and most people don't have the tools to do this with. I suggest that you send in the clutch for re-balance and clean up... this is THE primary connection from your motor to the sled make sure it is as spot-on as possible.
Once installed, the belt deflection can be set easily, take your time to do it correctly. (in your Owners manual)
New springs every season.
If you have a high mile clutch... Definately have it serviced.
The clutching system is the heart of your sled and its performance...This is the one area NOT to cut costs on.
Also, most 2005 900's that I've worked on have broken motor mounts that also affect the performance...unfortunately, you cant service these or even check them without pulling the motor...
Do a good job with your clutches and then look elsewhere.
Mountainhorse, I am still running my secondary the way it came and using MTX weights and the blue pink spring and it has been working great. This is the way the guys at SLP told me to run this sled.
What improvement would changing to your recommended helix and spring give me?
Also where is a good place to buy these?
Are they Polaris parts and if so do you know the part numbers?
What improvement would changing to your recommended helix and spring give me?
Also where is a good place to buy these?
Are they Polaris parts and if so do you know the part numbers?
M
MacDawg productions
Well-known member
Interesting post. So do you guys think hitting 8000 rpm is too high? I thought these motors where suppose to hit 81-8200rpm. I'd like to think that my machine is running top notch after the coin and maintenance time I have sunk into her. I believe I was running about 7800 last year, but I just did a top end/cylinder, vforce reeds, Fire n ice air box and Mbrp can, new 321115 belt. Is it possible to pick up a couple of hundred rpms? She's running beauty!! Snappy like a crocodile in heat!!
slp dyno charts show 7800 rpm is peak hp. if your runing 8000 rpm your at about stock hp. these engines do not like high rpm at all. stock 05 900 peak hp is 7450. higher rpm doesnt mean higher hp. hope that helps.
Just thought I would clarify something on my post. Mine holds between 7400 and 7500 while you are accelerating but if you hold it wide open long enough it spools up to 7800. Once in a great while it will hit as High as 8100 if you have it pointed down hill and pin it.
Zane..
the stock helix is junk, it creates belt heat, slowly backshift and is not a proper match to the P-85...you should be using the red/pink spring and the 66/44.46 or similar like 64/42.46, 66/44.42 (you wont hardly notice he difference between these) and use 3 derlin washers.
i know where a few of the helix's are, so i will send you the links...their like $50 used usually..
mac, your hitting too high on your RPMs...like triple said...the max perf from the 900 is 7800 rpm..so you wanna set it up to hit that...you will not believe the about of pull it can as that rpm...use the MTX weights so you can tune it closer..they rock!
Anyone have a clutch laying around they want to sell?
Primary or secondary? There are a couple guys who have primary clutches for sale.