2010 AK sled projects

[sonds]

Slow and steady wins the race right?

Which MCX kit are you runnin. Killer build will be keeping an eye on this one

 

[hugger70mtnmax]

I run the 162 Cat skid in mine. Last year I started out with the track fairly loose. This year I am adjusting per the Nytro instructions, or in other words pretty tight. The vibration issues that I was dealing with last year seem to be gone. I have also not noticed any issues with the track slapping around like it seemed to before. So it very well may be better on the longer track models. I am only running about 130 in the rear shock and the front shock is preloaded about two thirds of the way so those settings are not super agressive.

How do you like the polaris skis on your sled. I have been trying to think of any ways possible to remove weight from the front of this thing and I have heard that these skis are lighter. I am not prepared to save weight and lose performance however. Is there much modification required to mount them?

 

[Off Trail Mike]

It's just pre-filter material, it does work extremely well. You use to be able to get 18"x18" pieces at Ski-Doo dealerships for about $30.

I lowered the front arm of the cat skid another inch last night which was a PIA. I had to holesaw through my tunnel brace so the bolt would be against the flat of the tunnel. This was the only way to keep the back of the skid low for exhaust clearance and still have it sit completely flat. I only have 16.5" shocks up front too. I'm not sure how the guys with 17.5" shocks are running the front arm so high in the tunnel without there being a ton of preload on the rear shock. If I lift the back of the sled and lower it to the ground the skid sits perfectly flat and both shocks preload about the same(instead of most of it being on the rear). I'm hoping that will mean an improvement in bump absorption and ride quality.

I do wish these skids would maintain track tension. I have to keep the back of the skid mounted low enough that the track doesn't slap the header when the it's compressed. My Expert-X always maintained perfect track tension. Maybe the 153/162 suspensions are better?

I don't quite get why the 141 is so different. If I get a chance I'll lay it out in CAD to see why, as I have 141 rails too.

The 153 AC geometry is really quite different, and it is partially to do with AC M's super low angle of approach & Yami's 7 tooth drivers vs AC's 8's. When you go from yami 153 to AC 153, you loose an inch of ground clearance and the track is about an inch higher in the tunnel. Here's what the 153 AC looks like in my sled...finally installed.

Like your's, when I lower my suspension slowly, it touches down pretty much flat front to back and I can see weight coming off the front suspension which is good.

I'm with you on the 16.5" shocks, because they should be the right choice. If you lower the skid's ground clearance by an inch, you need to do the same with the skis to maintain balanced front/back pressure, although I am suprised ...... the 17.5's look like they will work. I'll try the 16.5's too.

My biggest concern is with the track being higher in the tunnel by an inch. I have 4.5" between the track and the top of the tunnel. I plan to put an undertunnel that is 2.25 - 2.375" thick, which gives me about 2.25" for the track to baloon at speed. Not sure if its enough, because if it isn't, I'm screwed as I can't easily lower the front mount like you did as I have no room to move the skid backwards, so moving the skid down screws your approach angle.

Final step is the undertunnel....now to find time to finish the damn thing.

OTM

 

[HYFLYR]

Sonds, its the 290hp kit. Dont think it will stay there long though. Probably going to run it a touch more than that.

 

[rlcofmn]

It's just pre-filter material, it does work extremely well. You use to be able to get 18"x18" pieces at Ski-Doo dealerships for about $30.

I lowered the front arm of the cat skid another inch last night which was a PIA. I had to holesaw through my tunnel brace so the bolt would be against the flat of the tunnel. This was the only way to keep the back of the skid low for exhaust clearance and still have it sit completely flat. I only have 16.5" shocks up front too. I'm not sure how the guys with 17.5" shocks are running the front arm so high in the tunnel without there being a ton of preload on the rear shock. If I lift the back of the sled and lower it to the ground the skid sits perfectly flat and both shocks preload about the same(instead of most of it being on the rear). I'm hoping that will mean an improvement in bump absorption and ride quality.

I do wish these skids would maintain track tension. I have to keep the back of the skid mounted low enough that the track doesn't slap the header when the it's compressed. My Expert-X always maintained perfect track tension. Maybe the 153/162 suspensions are better?

I don't quite get why the 141 is so different. If I get a chance I'll lay it out in CAD to see why, as I have 141 rails too.

The 153 AC geometry is really quite different, and it is partially to do with AC M's super low angle of approach & Yami's 7 tooth drivers vs AC's 8's. When you go from yami 153 to AC 153, you loose an inch of ground clearance and the track is about an inch higher in the tunnel. Here's what the 153 AC looks like in my sled...finally installed.

Like your's, when I lower my suspension slowly, it touches down pretty much flat front to back and I can see weight coming off the front suspension which is good.

I'm with you on the 16.5" shocks, because they should be the right choice. If you lower the skid's ground clearance by an inch, you need to do the same with the skis to maintain balanced front/back pressure, although I am suprised ...... the 17.5's look like they will work. I'll try the 16.5's too.

My biggest concern is with the track being higher in the tunnel by an inch. I have 4.5" between the track and the top of the tunnel. I plan to put an undertunnel that is 2.25 - 2.375" thick, which gives me about 2.25" for the track to baloon at speed. Not sure if its enough, because if it isn't, I'm screwed as I can't easily lower the front mount like you did as I have no room to move the skid backwards, so moving the skid down screws your approach angle.

Final step is the undertunnel....now to find time to finish the damn thing.

OTM

Keep this in mind when you figure your undertunnel... How much I fought exhaust clearance and the ill effects of changing your skid to clear exhaust is why that chassis is in a snowbank for a death bed.

I should reincarnate that sled since I won't be fighting exhaust with the turbo then I'll have a long sled for all the deep days we seem to be getting this year. Or get my tubie done :exc:

 

[Off Trail Mike]

Thanks for the heads up Rlcofmn, I saw those pic's on the original build and never forgot them....makes me wonder if an undertunnel will ever work.

I'm using a Vector header which moves the silencer forward as far as practical, unless you butcher the header...not prepared for that just yet. At least the Vector header adapts to 2" exhaust tubing, and not 2.25 like the nytro, so I can keep the silencer thinner

I am thinking of fabricating a 16" x 8 x 2.25" slilencer with 2" inlet and an oval outlet in the back....maybe 4" wide x 1" thick. The plan is to taper the rear of the silencer up to meet the oval outlet, kinda like the outlet of a yoshi RS5 but a much longer taper. So if (when) a lug does catch it, both the muffler and the paddle will receive a glancing blow.

Hopefully this will keep the entire muffler forward of the upper idler wheels by 4 or 5 inches, so I am hoping its enough, otherwise I'll be building a new block off plate with a raised section for a silencer...and that would be a royal PITA.

OTM

On second thought, I think I'll drain the air out of the rear float and collapse the skid to see what's in there for room, but I'll bet you I don't have 2-1/2" in the back!

 

[Nikolai]

How do you like the polaris skis on your sled. I have been trying to think of any ways possible to remove weight from the front of this thing and I have heard that these skis are lighter. I am not prepared to save weight and lose performance however. Is there much modification required to mount them?

They're not the best skis, but I do feel they're an upgrade from the oem MTX skis. They definitely track straighter and don't catch edges like the oem skis do. For the cost I think it's worth it. I got mine brand new for about $200 with carbides and it's almost a 5 lb weight savings. Only thing needed to mount them was narrowing the spindle bushing and I used the Polaris rubbers. MTX rubbers would probably work if you narrowed them though. Oh yeah, the traction nubs on top are awesome, all skis should have them.


My issue wasn't ballooning. My track was smacking the header/exhaust when the skid would collapse and no longer had track tension. I hadn't done damage yet but it was only a matter of time. I don't have an M sled to measure but they have to sit at least a couple inches lower at the belly pan.

 

[Nikolai]

Our setups look identical to me except your front arm is a little higher. Other wise the rear scissor, lower shock linkage angle, ect. all look the same. Before I took my picture I sat on the sled and then hopped off. I assume you did the same thing? What do you weight? I'm about 185 lbs dressed. One thing I would like to try is a longer front track shock. I think a +1" shock would allow the front arm to move back up but still keep some pressure on the front of the rails. Someone on Snowest used a longer Firecat shock and was happy with the results.

 

[Off Trail Mike]

Caleb:

Yep, I got on and off the sled...and I'm 205 lbs dressed.

You're running the 12-1/2" XF shock and not the 11-1/4" M front shock right? Thought I'd throw it out there, as this would make a really big difference, but I don't even think the 11-1/4" will fit the 141 rails. It would be worth trying the longer shock up front, should help put more pressure on the front of the skid too.

So here's the pick of the 141 rails up to the 153, and their identical except for difference. The approach angle is steeper on the 141 by maybe 5-7 degrees. Its not too noticable in the picture but look just back of the antistab. With a steeper approach, your front holes should be lower in your tunnel and slightly ahead.

Are you finding that you have too much weight on the skis or just an issue of track tension?

 

[Nikolai]

The only issue I've had is track tension. My skid should have the 11 1/4" shock but I'll double check after after work tonight.

 

[beeze455]

The below picture is my skid setup with the shaft out waiting for extros. With my standard drivers it ratcheted on throttle. I put the extros on and it stopped ratcheting, but made a noise when slowing down. Rode it and it started ratcheting when I hit a hard bump and pushed the throttle. Then it started to do it when I climbed hills.

said screw it and tightened it up on the side of the trail. Gotta see how tight it is, but it is tight. No more noise on slow down or ratcheting.

 

[hugger70mtnmax]

My issues I was having with the track loosening was when the rear suspension would compress a lot. The worst times were when cresting a hill with a bump at the top where I could feel the skid compress. I have not had the same issues with the track tighter.

It would be interesting to poke around on the cat forums a little to see if they have this problem at all.

 

[Nikolai]

So what are you guys running for track tension? I think it would be interesting to compare with so many of us running AC Float skids.

Please state:
- skid length
- track length
- tension and how it was measured

I will measure mine as soon as I get a chance.

 

[hugger70mtnmax]

I am running mine so that there is just barely enough droop so that the nubs on the track are just below the hyfax in the very center. This is not pulling on the track but just allowing it to hang. My setup is a 162.

 

[Off Trail Mike]

153 and if I measure like huggermax in the middle, maybe 1/4 of gap between the lug and the hyfax at rest (or 3/4" between steel track clips and hyfax)

Also, Caleb pretty sure you should be running the 12.5" shock up front for a stock CF suspension stock set up. When I bought my suspension, I got a complete 141 CF suspension which came with a 12.5. I bought the 153 rails and 11.25 shock separately. I have a Fox Zero Pro 12.5 if you want to try it out. The springs are the same length and rate as best I can tell.

OTM