Did you end up weighing the 800 motor before you put it in?
Polaris RMK 800 snowbike
- Thread starter Brett Kobernik
- Start date
No I dont. Maybe once I get serious about it ill start to document it and do a build thread. Funny tho the second I put a belly pan on it nobody is interested because its a "snowhawk".
Do you get the gyro effect from the clutches with these builds?
Tell those boys to put a CVTech clutch on , get rid of those big honking drag clutches . Makes a noticeable difference in the gyro and throttle response .
Totally over looked clutches used in applications of many many manufactures .
It's what makes a sleeper
Totally over looked clutches used in applications of many many manufactures .
It's what makes a sleeper
No, but I took it out today to finish welding the frame. I'm calling it 83lbs with the primary, throttle bodies and a few other misc things on it.
Well, their loss, Hawks are cool. Lightweight dirt bike powered snowbikes are cool also until you get a foot of new snow and can barely go anywhere.
I think the Unicorn is perhaps the best machine to give an honest answer. I rode it for years (since 2012) with a KTM 520 RFS engine. Last spring, I stuffed the Arctic Cat (Suzuki) 580 in it without changing anything else. Same exact suspension. I didn't notice anything different except all of a sudden I was climbing crazy lines that nobody could follow. If anything it handled better because of being able to spool up the track so fast when in tight cornering. I've heard the gyro argument in the past. I'm not buying it. I suspect that a lot of people form an opinion about something without actually doing a real honest comparison.
I gotta research your suggestion. Never heard of those.
The clutch threw out it's range keeps the weights/pucks to the center of the clutch instead of flinging them outwards . If your accustomed to your machine and switch to this clutch it'll even catch you off balance because your accustomed to some riding characteristics that you don't realize compensating for the gyro . Throttle response is much quicker also . I posted a short clip somewhere on here , 800 CC engagement 2850 and no bog or belt slipping . Big benefit is finessing difficult situations .
The Yamaha 4 stroke sled guys really like them and their running 200 ponies with a ton of low end .
Polaris even uses it in their 550 sled probably because thier traditional primary is like throwing sledge hammers for that little guy .
Wheelers and side by sides of many manufactures use them so they have extensive knowledge .
Very easy to tune
The Yamaha 4 stroke sled guys really like them and their running 200 ponies with a ton of low end .
Polaris even uses it in their 550 sled probably because thier traditional primary is like throwing sledge hammers for that little guy .
Wheelers and side by sides of many manufactures use them so they have extensive knowledge .
Very easy to tune
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I pulled the machine apart to finish welding and painting the frame. 27lbs. Gonna have to live with that for this build. I’m pretty sure I went way overkill because of worries about it breaking somewhere. I’m already brainstorming about the next lighter weight build, if indeed this one works out as good as I hope.
My coach wasn’t impressed with the weight of the frame. His response was “start drilling holes”. This prompted me to take an abrasive cut-off saw to it and remove unnecessary metal. Ditched almost 4 lbs. Should’ve looked more critically at this earlier on.
Closing in on it now. I had it running yesterday. My initial impression was it’s a little louder than stock but WAY quieter than the Unicorn. Should be on the snow next week.
Finished the oil tank. Kawasaki jet ski filler neck and cap clamped to a piece of rubber fuel filler hose which gets hose clamped to the fitting on top of the tank. Smaller buna-n hose comes off the front of the tank and acts as a sump.
Got the engine back in, routed the fuel lines to the tank and finished all the wiring. I was able to use the stock wiring harness without any changes. I had to lengthen wires up to components on the bars but otherwise, all the stock wire lengths work for reaching all the components under the hood. For now, I taped and zip-tied the throttle safety switch so it’s “on” and tucked it under the hood. I’ll be running a tether on this beast, no question.
Finished up routing the coolant lines. Finished the prototype airbox. Still need to finalize the jackshaft mounting, mount the brake, secure the coolant reservoir and finish up the plastic covers and a few other small things.
Closing in on it now. I had it running yesterday. My initial impression was it’s a little louder than stock but WAY quieter than the Unicorn. Should be on the snow next week.
Finished the oil tank. Kawasaki jet ski filler neck and cap clamped to a piece of rubber fuel filler hose which gets hose clamped to the fitting on top of the tank. Smaller buna-n hose comes off the front of the tank and acts as a sump.
Got the engine back in, routed the fuel lines to the tank and finished all the wiring. I was able to use the stock wiring harness without any changes. I had to lengthen wires up to components on the bars but otherwise, all the stock wire lengths work for reaching all the components under the hood. For now, I taped and zip-tied the throttle safety switch so it’s “on” and tucked it under the hood. I’ll be running a tether on this beast, no question.
Finished up routing the coolant lines. Finished the prototype airbox. Still need to finalize the jackshaft mounting, mount the brake, secure the coolant reservoir and finish up the plastic covers and a few other small things.
First test went well. Just enough snow in the backyard to spin a few circles. Gonna try to get it into the high country tomorrow.
I love the flat foot seat height!
Had a slight hiccup. Engine wasn’t running right, low idle, no snap when pulling the throttle. Tried a few things then swapped out the ECU. Freaking thing wheelies from a dead stop now. Hopefully hit the hills with it the next few days.
Money.
Now that is cowboy!
I am so pleased with how this machine turned out. The initial test rides have been great. Still a bunch of fine tuning to do.
I’m only getting 7100rpm out of the engine right now. Should be around 8200 wide open. I’m fiddling with intake, exhaust and clutching to try and figure out what needs to be tweaked. Trial and error methods. I’m sure I’ll get it dialed.
My buddies came up with me for a day and we brought out the Unicorn and the Yamalaris so we could switch off and get a feel for them both. We all decided that the Unicorn has a better rider position mainly due to the seat being too low on the Yamalaris. The Unicorn has an aggressive feel when sitting. The Yamalaris feels too much like a chopper.
So, I took my old seat with a torn cover apart and layered in some more foam. Walmart “deluxe” camping pads are easy to work with along with some spray on adhesive. I brought it up to the same height that the seat is on the Unicorn. This seat now also has a little turn up at the front of it which should help hold the rider from sliding forward while descending slopes. Still have some trimming and sanding to do.
The other thing that needed attention was the pegs. The pegs I originally mounted were only for testing. They were an inch lower than the pegs on the Unicorn. So, I installed these aluminum pegs on some aluminum mounting brackets. They are the same height as the pegs on the unicorn now. I lost 2.5lbs switching from the metal test pegs to the aluminum. Every little bit helps!
Now, the rider position should be damn close to the same as the Unicorn. Got some seat cover material coming in a few days.
My buddies came up with me for a day and we brought out the Unicorn and the Yamalaris so we could switch off and get a feel for them both. We all decided that the Unicorn has a better rider position mainly due to the seat being too low on the Yamalaris. The Unicorn has an aggressive feel when sitting. The Yamalaris feels too much like a chopper.
So, I took my old seat with a torn cover apart and layered in some more foam. Walmart “deluxe” camping pads are easy to work with along with some spray on adhesive. I brought it up to the same height that the seat is on the Unicorn. This seat now also has a little turn up at the front of it which should help hold the rider from sliding forward while descending slopes. Still have some trimming and sanding to do.
The other thing that needed attention was the pegs. The pegs I originally mounted were only for testing. They were an inch lower than the pegs on the Unicorn. So, I installed these aluminum pegs on some aluminum mounting brackets. They are the same height as the pegs on the unicorn now. I lost 2.5lbs switching from the metal test pegs to the aluminum. Every little bit helps!
Now, the rider position should be damn close to the same as the Unicorn. Got some seat cover material coming in a few days.
My suspicion is that the airbox is
part of your culprit for low rpm.
do some searching on “gutted airbox” on pro rmk sleds. (Most guys lost low end power and peak rpm when the air horns / shelf was removed)
The pipe also changes the “powerband” when modified. You need to account for the material lost in the cutting/ fitting process. I added a 7/16” ring into the fattest part of my skidoo pipe i modded to fit my home built snowbike.
having a different powerband can also be partially compensated for with clutching and gearing. Pro rmk sleds are high geared to begin with stock and i had great luck gearing them down 20% even though i ride close to sea level.
drop your primary clutch weight 4 grams and gear it down a bit should transform your performance.
(all this is assuming your engine internally is performing correctly)
a bad exhaust valve solenoid can be diagnosed by plugging the line going to it and seeing if the peak rpms raise.
Wow did it run right before the project? losing over 1000 rpms on a cvt would mean you lost well over 20hp! that's more than half the power a 450 even makes at 10000 feet!
I Doubt the pipe or intake could make that big a change by them selves unless you drastically screwed up the pipe angles. Check the power valves for sure. If you cant tell that they are getting 100 percent open see if there is a way to jam them manually open for a test.
Also check the clutch aligment and all the rollers and bushings in the clutches.
I Doubt the pipe or intake could make that big a change by them selves unless you drastically screwed up the pipe angles. Check the power valves for sure. If you cant tell that they are getting 100 percent open see if there is a way to jam them manually open for a test.
Also check the clutch aligment and all the rollers and bushings in the clutches.
A pipe could make all the difference. I tried a set of twins on a 2007 ski doo rev that were made for an 800ho not an 800r and I lost huge amounts of rpm at elevation. But without a dyno to adjust things its anyone's guess what's going on.
You might have to try a fuel controller to get it dialed.
You might have to try a fuel controller to get it dialed.
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