Air Box Delete

I got tired of trying to keep the snow out of my airbox so I decided to delete it and try something different. I also have been having some carb icing issues so I installed a KTM carb heater. For the intake I used a 3" chunk of 2.5" silicone hose that just barely slide over a 2"X3" ABS reducer I then used a 3" - 22.5 degree ABS elbow to clear the subframe and then drilled out a 6" long piece of 3" ABS to use for my prefilter cage which I will be running an outwears prefilter over. Installing the carb heater was a lot easier than I thought it was going to be and aside from drilling a hole in the carb and tapping it for the heat probe everything was plug and play.

I haven't taken it out on the snow yet to see how this new setup is going to work but I am headed out Monday and I will report back. My bike is looking pretty bare with the radiator shrouds being the only plastic left on the bike but I am thinking this new intake should give me a lot less problems.

Initially I was going to make it more of a snorkel and run it up to the back of the seat with 4" ABS because I didn't think the 3" was big enough but I can't find a prefilter to fit over 4" ABS so I am going to try this and see how it works. I agree a lot of snow gets thrown through the subframe of the kit but I am hoping it just falls off of the prefilter and doesn't effect airflow that much. I will let you know how it works after Monday's ride.

I started off the season running just the prefilter and filter cage without the foam ( I see no need to use the foam filter) and the bike has ran good until I get snow in the airbox. As for sealing the airbox I had spent quite a bit of time and effort to seal it and somehow I was still getting snow in it when the powder was deep. I also don't like that any moisture that gets into the box ends up in my intake because that is the lowest point in the airbox. I am not to worried about any restrictions with the intake I built it should flow plenty of air for a little 300, I have seen sled intakes much long and restrictive feeding much bigger motors. I am going to take some duct tape with me and if it seems I am having to much snow coming through the subframe I will tape off the openings. I am headed for the mountain tomorrow and I think we are going to have about 2' of fresh so it should be a good test, I will report back.

more snow said:

It also would be a good idea to put a ziptie or hose clamp where the prefilter material seals up against yoiur black pipe setup. Otherwise, snow will work past this interface.

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I don't think I really needed the zip tie to keep the snow out because the elastic sits behind the lip of the collar on the elbow but as a safety precaution and for piece of mind I did put a zip tie around it. Overall the intake performed very well and was noticeably better than the airbox especially considering the snow conditions. We were riding in about 2' of pretty fluffy powder the type of snow that likes to get into your airbox and ruin your day. Even with the intake as low as it was and the constant snow being thrown on it from the track it never got completely covered or clogged up, most of the snow just fell off of it. When I stopped I usually just brushed what snow was on the prefilter off. I think the engine is getting plenty of air from the intake although I may have noticed a tiny bit more hesitation low in the rpm but it could have been my jetting to I will have to ride it more to see what the culprit is. Another problem I had was on the road ride back to the pickup the bike started running rough and would die as soon as I let off the gas, when I got home I pulled the intake of and found water droplets all over inside the intake and I am betting my float bowl is full of water and that's why the bike was running so rough. So the prefilter is letting moisture through in one form or another which is probably happening with every snobike setup but to combat this I am thinking about adding some isopropyl to the gas so the water mixes instead of collecting in the float bowl. As for carb icing I think I may have experienced it once thoughout day when the bike didn't want to idle very well but it could have been the water in the fuel to it's hard to say. I also need to verify that my carb heater is working, I put my finger on it after the bike had been running for awhile and didn't feel any heat so I may have a wiring issue or it may not get that hot at the top of the probe I will do some testing this week.

As of right now I am happy with the intake and am going to continue running it, I feel like it's going to give me a lot less problems than my airbox. A previous comment on this thread stated that the KTM airbox's are easy to seal up and I would agree with you if your talking about the older airbox design as I didn't have near the issue with my 06 525 as I have had with my 09 300 airbox. I think the newer KTM's 11 and up have a different airbox design that is more forgiving in regards to keeping snow out.

Leftys said:

The kit looks good. The only thing that I see that can potentially be a future problem is there is no support at the pre-filter end of the tube. The weight hanging off of the carb is a lot of stress on the carb to cylinder intake boot, especially with the vibration of the engine. Something may be there, but I am not seeing it.

On the idleing and water in the Float Bowl situation. Here is what I have found: The Jet Needle is iceing up so when you close the throttle slide the Jet Needle goes into the Needle Jet and blocks fuel flow and emulsification with the air creating a lean condition, which will not let the engine continue to run. When the ice melts off of the Jet Needle the water drains straight down into the float bowl. After a few times of this happening you have water in the bowl.

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The intake is supported with the white ziptie that goes around my strud rod, it does a pretty good job but I want to figure out a better method.

Your water in the float bowl diagnosis sounds legit I think next trip out I am going to try wrapping some insulation around my carb and I need to verify if my carb heater is working. If I can keep the carb from freezing it sounds like I may resolve my water issue.

anonny said:

Hows about a crazy carpet ziptied to the upper frame to act as a fender for the offending snow being thrown?

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That's a good idea I think I will do something like that.

I now have two ride on this intake in 2ft of powder and am having minimal issues compared to the airbox setup. I didn't get time to address the issue of snow coming up through the subframe on the kit or wrap my carb with anything and it still ran pretty good. About halfway through the day I had to turn my idle up to make it idle but other than that it ran good. I really do need to put something around my carb though because it is completely covered with snow all day and I don't think that little carb heater can compete very well against that. I also know that I was sucking snow into the carb but it didn't seem to effect performance of the bike, the powder was so dry that it must have been making it's way through the prefilter because I could see snow inside my intake.