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2003.5 Arctic Cat Mountain Cat 900 powder bog

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    2003.5 Arctic Cat Mountain Cat 900 powder bog

    Just bought a Mountain Cat. Previous owner said he pulled off some crazy airbox setup and went back to stock. It had 370 main jets, I tried switching to 360 and then 350 mains and it runs a little crisper and plugs look better. Problem is that it still bogs anywhere but flat trails. If I go up a steep hill or lay it over to carve left or right, it bogs out and runs at like 60% power. It seems to bog faster when carving to the right side where the exhaust is. It has an SLP single pipe and can. It's not sealed to the belly pan like some people say that you should do. It does seem to get some snow in the right side, either from the exhaust outlet in the belly pan or the right side intake. I've heard of a variety of fixes that don't fully fix the problem. Most people, from what I've read on arcticchat and other forums are just trying random stuff with a variety of success or lack thereof. I'm wondering about doing individual filter pods right on the carbs themselves so I can't be pulling powder through the stock airbox and its ****ty prefilters. I have a hard time believing that the powder plugs the exhaust enough to kill the power. Also, the power doesn't come back immediately once the exhaust is clear. I've been able to carve circles around to the left with the exhaust totally clear of the snow and it still bogs.

    Carb float height--it seems waaaaay too high compared to my dirtbike carbs. The floats look like one solid piece of plastic and the height isn't adjustable. It seems that with the float level so high it would flood out when I rock it over or climb a steep hill. Seems to match the symptoms. If the floats aren't adjustable, then WTF? Also, if the floats were set way too high, wouldn't there by symptoms when riding flat land too?


    The sled flat out rips on the trails. It starts and idles just fine too.
    Trevor

    Fully addicted moto-junkie

    #2
    Sandman has owned one of the cats. I'm sure he would know.

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      #3
      Taped off the intake hole right behind the brake. When snow hits the pipe I think a blast of steam goes right into the airbox making it run rich. Many places in other forums I saw suggestions to tape off this hole.

      The bedliner I cut up for ski glides just keeps on giving. I found a part of the side wall that should make a decent exhaust deflector. Will it hold up to the heat? I don't know.


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      Trevor

      Fully addicted moto-junkie

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        #4
        Click image for larger version

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        Riveted and JB Kwik Weld
        Trevor

        Fully addicted moto-junkie

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          #5
          Punched out my running board holes too while I was working on the sled. They're pretty aggressive now.

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          Trevor

          Fully addicted moto-junkie

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            #6
            I'd take a holesaw and cut them out and add a couple more, then use some sheet metal screws with 5/16's heads for traction. That's Cheap or for a little money buy a set of feethookers and install them. If the bedliner melts a piece of sheet metal will do the trick. 2 or 3 inch bar riser will make it a lot more comfortable to stand up on. I always ran my front shocks super loose to help it roll easier. When it gets below 20 those motors get to be very hard to pull over when they are cold, went through a few recoils until I finally spent the 30 bucks for a block heater, splices right into the coolant bottle hose and just plug it in for 20 minutes and it pulls over first time. Be careful putting your knee too far back on the seat, those seats break down in the rear above the storage compartment pretty quick. If the driveshaft bearings haven't been changed recently I'd make that priority one on your list, I'd do it every 1000-1500 miles. If your speedometer quits working that's a sure sign the bearing's are totally shot.

            If your fixes don't help your bog you might check the smart valves/fuel lines in your tank. Need a little more info on exactly what it's doing to help more. Might check the slack in your throttle cable and make sure its not a tors problem.
            Last edited by 89sandman; 12-24-15, 12:34 AM.

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              #7
              Absolutely perfect conditions today. Couldn't ride in the powder for more than a few seconds until it bogged down and definitely couldn't carve to the right.

              I've done some more reading and it appears the only fix is to get the exhaust to exit out the shock tower like the '06 King Cat.

              **** thing rips on the trails or in just a few inches of powder. As soon as you punch in deep it starts to bog. What a stupid design.

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              Trevor

              Fully addicted moto-junkie

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                #8
                Just a thought try and put the exhaust were it exits in a different place.

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                  #9
                  Originally posted by Petrolburner View Post
                  Absolutely perfect conditions today. Couldn't ride in the powder for more than a few seconds until it bogged down and definitely couldn't carve to the right.

                  I've done some more reading and it appears the only fix is to get the exhaust to exit out the shock tower like the '06 King Cat.

                  **** thing rips on the trails or in just a few inches of powder. As soon as you punch in deep it starts to bog. What a stupid design.

                  [ATTACH]6487[/ATTACH]
                  Could still be some of the items sandman listed- check throttle cable adjustment and fuel pick ups in the tank.

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                    #10
                    might need that crazy airbox setup back on there.

                    Comment


                      #11
                      Probably going to get some good photos and list it for sale since my brother just told me he would be able to go to Baja to meet up with my Dad down there and go fishing for two weeks. I'm going to need to sell a motorcycle or the sled to raise the cash.

                      I also think the diameter of the silencer is too big. With the huge diameter, the velocity is too low and allows it to plug up. Seriously, this thing is huge. Even my 4 stroke stuff doesn't need an exhaust with that big of a diameter. Perhaps just a reducer on the outlet would solve the problem. Plenty of sleds have the exhaust exit out the bellypan without problems. There's no good reason a 900 twin can't do the same.
                      Trevor

                      Fully addicted moto-junkie

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                        #12
                        Sell that 2wd yellow thing. Get a modern sled and go to baja. Remember all the hooting and hollering you were making when you rode mine for a few minutes. More months out of the year here are good for snow than a 2wd/RWD racecar
                        Last edited by KTMDirtFace; 12-29-15, 12:20 AM.

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                          #13
                          Originally posted by KTMDirtFace View Post
                          Sell that 2wd yellow thing. Get a modern sled and go to baja. Remember all the hooting and hollering you were making when you rode mine for a few minutes. More months out of the year here are good for snow than a 2wd/RWD racecar
                          All true, but Timbersled, not modern sled.
                          Trevor

                          Fully addicted moto-junkie

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                            #14
                            Rode yesterday to test out my exhaust outlet reducer. Seemed to work great and I was able to carve continuous right circles without bogging. Exhaust outlet diameter was too big, velocity was too low. By reducing the diameter the velocity increases and kept it blown out and clean. I also listed it for sale last night on Craigslist. Got two hits right away by people that didn't have quite enough money.
                            Trevor

                            Fully addicted moto-junkie

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