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Discussion Starter #1
I learned something from a friend this week that blew me away , he snorkeled a Suzuki King Quad and it wouldn't run right , he tried changing jets , he used 2" pipe on the snorkel , another friend of mine has a ATV shop and I suggested he bring it to him and let him have a shot at it , so he took a shop rag and doubled it up and taped it over the snorkel inlet to restrict the air flow , buddy said it ran better , he then made the rag 4 layers and taped it up again , it was even better , then they went 8 layers of rag and the bike screamed , so he says the snorkel pipe is too big and he should change it to 1 1/2" pipe , I suggested he could make an orifice out of a bushing and install it into the pipe
 

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Interesting, I'd have never thought over sized pipe would have caused an issue, you'd think the engine would only let in what the carb would allow.
That said, mine ran better when I split my snorkel (1 1/2") and just left the flexi hose on, I've since bought a 1 1/2 to 2" reducer and used a 2" pvc pipe off the flexi and it runs great.
 

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Discussion Starter #3
I run 1 1/2 pipe on my 300's and it works for me ------------------- seems some bikes are temperamental , I seen where the motor runs great with the air box cover off and when you put it on the motor would stave for air , much the opposite of having too much air like whats going on with the Suzuki , my buddy is snorkeling his new to him Yamaha 400 today , he is a good carpenter but a jack leg mechanic , can't wait to see what he comes up with ------- something else with Yamaha , it seems some of their engines need the crankcase vent tube to stay in the air box and not be run up with the snorkel , I have seen it twice now where the bike runs like crap till you move the vent back where it was OEM
 

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That phenomena is caused by the moving column of air in the snorkel having a greater mass than can be controlled/mitigated by the induction system. Proper tube sizing vs tube length solves the problem. Its a physics thang... so there's lotsa math explaining that. :-(
 

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Discussion Starter #5
`I have often wondered while consuming beverages , when the bike goes deep in the water and the snorkel tubing is under water , does it make it harder for the engine to suck the air , kinda like when you go snorkeling yourself while swimming , ever noticed the deeper you go the harder it is to suck air , you never see swimming snorkels longer than the standard length
 

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The motor is not flexible like the human ribcage and body, so it only "sees" the atmospheric pressure in the snorkel no matter the water depth, provided all vents for the crankcase & carb are in that snorkel air supply. The only function of the motor that has to overcome rising pressure from increasing water depth is the exhaust... then only if it hasn't been snorkeled to the surface. There is a point where rising pressure at extreme depths will overcome the rigidity of the cases and collapse them, but no human would survive the ride down there to see it... lol

Swamp racers usually snorkel both intake and exhaust. Then full power is available at the bottom... can even stop and let it idle a minute while lighting up a smoke if they got 'em... :)
 

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The physics and math behind snorkeling suggest that the inlet of the snorkel tube be matched closely with the volume of air requirement (in CFMs) of the motor at WOT/Max RPMs. The entry point is the smallest diameter of the pipe, in other words. From that entry point onward toward the plenum & carb/vents, the tube should gradually expand in diameter/size/volume, so that the moving air column in the tube will gradually slow down. Ideally the air column should come to an almost complete stop... providing adequate air supply, but at or above atmospheric pressure.

Racers learned decades ago that the final approach to the plenum (aka airbox) should increase in volume equal to 15 degrees of angle expansion on parallel walled (square tubing) tubes. "Dead air" under high pressure (equal to or greater than atmospheric = 14.7 PSI at sea level) at the carb is the goal...

As the velocity of air increases, the air pressure decreases (and vice versa). Low pressure is bad for making power.... and fast moving columns of air are excessive kinetic energy producers, so snorkel design can be pretty important depending on what you are trying to optimize for.

Boring stuff really.... I hate doing the math...
 

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I have been considering running a snorkel for 420. Seems like consensus is running a 1 1/2" pipe. I have a big chunk of 2 1/2" Hot Tube flex that I was going to run for my old 700 King Quad. Is that going to be too large for the 420? and how many vents lines are there to run?
 

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If I were snorkeling a 420 I would put a short 1.5 inch opening at the top of it, then increase pipe diameters in a couple steps. I'd just wing it... design something that you like and works for you.
 

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The physics and math behind snorkeling suggest that the inlet of the snorkel tube be matched closely with the volume of air requirement (in CFMs) of the motor at WOT/Max RPMs. The entry point is the smallest diameter of the pipe, in other words. From that entry point onward toward the plenum & carb/vents, the tube should gradually expand in diameter/size/volume, so that the moving air column in the tube will gradually slow down. Ideally the air column should come to an almost complete stop... providing adequate air supply, but at or above atmospheric pressure.

Racers learned decades ago that the final approach to the plenum (aka airbox) should increase in volume equal to 15 degrees of angle expansion on parallel walled (square tubing) tubes. "Dead air" under high pressure (equal to or greater than atmospheric = 14.7 PSI at sea level) at the carb is the goal...

As the velocity of air increases, the air pressure decreases (and vice versa). Low pressure is bad for making power.... and fast moving columns of air are excessive kinetic energy producers, so snorkel design can be pretty important depending on what you are trying to optimize for.

Boring stuff really.... I hate doing the math...
Hmmm. I've decided to snorkel one of mine. I normally don't ride deep, but I picked up a 500 beater than is cut for a snorkel, and I just got a 450 swingarm in a bunch of parts so I'm going to put that swingarm on my 06 to stretch it out a bit, run 28's, and put a snorkel on it using those beater fenders. That way when I'm chasing a duck or picking up decoys I don't have to worry about sinking a bike if I hit a dang beaver run.

So You're saying run something like 2" out of the air box to a coupler, and then go smaller towards the end?
 

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The physics and math behind snorkeling suggest that the inlet of the snorkel tube be matched closely with the volume of air requirement (in CFMs) of the motor at WOT/Max RPMs. The entry point is the smallest diameter of the pipe, in other words. From that entry point onward toward the plenum & carb/vents, the tube should gradually expand in diameter/size/volume, so that the moving air column in the tube will gradually slow down. Ideally the air column should come to an almost complete stop... providing adequate air supply, but at or above atmospheric pressure.

Racers learned decades ago that the final approach to the plenum (aka airbox) should increase in volume equal to 15 degrees of angle expansion on parallel walled (square tubing) tubes. "Dead air" under high pressure (equal to or greater than atmospheric = 14.7 PSI at sea level) at the carb is the goal...

As the velocity of air increases, the air pressure decreases (and vice versa). Low pressure is bad for making power.... and fast moving columns of air are excessive kinetic energy producers, so snorkel design can be pretty important depending on what you are trying to optimize for.

Boring stuff really.... I hate doing the math...
Hmmm. I've decided to snorkel one of mine. I normally don't ride deep, but I picked up a 500 beater than is cut for a snorkel, and I just got a 450 swingarm in a bunch of parts so I'm going to put that swingarm on my 06 to stretch it out a bit, run 28's, and put a snorkel on it using those beater fenders. That way when I'm chasing a duck or picking up decoys I don't have to worry about sinking a bike if I hit a dang beaver run.

So You're saying run something like 2" out of the air box to a coupler, and then go smaller towards the end?
The other way around worked great for me jeep, I ran 1 1/2" silicone flexi from the airbox to a 2" pvc pipe.

Edit: That was a poor description on my part!

I ran 6" of 1 1/2" pvc pipe from the airbox, then silicone flexi to a silicone 90 degree bend. The bend is 1 1/2" to 2". From there the 2" pvc pipe with a silicone 'U' bend on top to keep the rain out.
(We get lots of rain here in England!)
 

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If you are leaving the stock airbox on the bike just about any snorkel design might work. If it doesn't when you get it on, just restrict the entry down to about 1.5 - 1.75 inches and that should fix it.
 

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After reading many threads over the past week, I have decided that I am going to go ahead and put a snorkel on my 420. Going to run 1.5" all the way, seems to be the consensus on all forums, and come out at the front where the "Fourtrax" decal is located. Going to run new vent lines and add dielectric grease to all electrical connections. I do live about an hour away from the closest hardware store, so I want to make sure I am well supplied before starting. Does anyone know what size the vent lines are? How do people typically secure the riser coming out of the bike?
Will take any tips or suggestions.
 

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Discussion Starter #16
I use u-bolts to secure the tubes to the front rack and to the frame under the fender and straps to secure it to the engine bolt with a bracket , vent tube I quit using rubber hose and use poly tubing used for air on big trucks , it pushed on to the barbs tight and you don't need clamps
 

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I also use U bolts to hold the main upright of the snorkel. For the vent lines I used 3mm i.d. silicone hose, pushes on great, heat & fuel/oil resistant, doesn't need clamps and is really flexible. @fishfiles idea of using poly tubing for vents is also a good idea, it's very durable and won't crush when you attach the lines to your frame with cable ties.
 

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I use u-bolts to secure the tubes to the front rack and to the frame under the fender and straps to secure it to the engine bolt with a bracket , vent tube I quit using rubber hose and use poly tubing used for air on big trucks , it pushed on to the barbs tight and you don't need clamps
I will be sure to have some u-bolts kicking around. I have lots of poly in my work van that I was going to run for vent lines. Just haven't been able to find any information on the vent line sizes. @fishfiles did you do any work to the air box? I'm not looking to go swimming or anything just want the extra protection. Seems like every year the trails keep getting deeper and deeper, not sure if its the side x sides but when it rains here the holes can get deep.
 

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Discussion Starter #19
1/4 poly tubing is the right size , like 1/8 id ----- the crank case hose I used 3/8 rubber fuel hose ------------- on the air box , I used a 1 1/4 " piece of pvc , glued to a bushing that is 1 1/4 female by 1 1/2 male , then a 1 1/2 collar , glue them pieces into the rubber inlet grommet of the air box with 3M5200 and I silicone the cover down with clear silicone , it covers off easy if need be ------I have two pvc pipes coming up , one has all the vents and crankcase hose inside of it , looks better and they don't flop around , there are a lot of vent tubes , don't forget the carb vent , on my 300 there is two diff vents , transfer case vent , carb , 2 front brakes , one rear brake , and crankcase , that was 8 vent tubes , by adding front disc , it got rid of two vent tubes
 

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Well that does it. All questions answered. Hahahhaha. Guess I'm in the market for some good 3/8" tubing, I'm sure the boat shop, I do some work for, will have something there tomorrow. Easier than going to the store. Thanks.
 
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