350x intake on 300ex?

[mike maddrell]

i think i read somewhere that you can use a 350x intake tube on a 300ex, has anyone here done this or have any experience with this? just curious how well it bolts up and fits. thanks in advance.

[enduro400rider]

it wont do anything for performance, if anything it will leave a gap around the tube and carb, you only use a 350x boot if your using a 400 carb, just the tube alone wont do anything

[bwamos]

Originally posted by mike maddrell
i think i read somewhere that you can use a 350x intake tube on a 300ex, has anyone here done this or have any experience with this? just curious how well it bolts up and fits. thanks in advance.

It's a myth IMHO.

I bought one to mount up with the 400ex carb.
The carb side is actually a tad smaller than the 300ex. It is a stiffer rubber so it wont even stretch well. It also has a different bend so it interferes with the upper shock mount and if you force it down the lip is at a significant angle to where it would never mount up well.

I jsut ended up using a heat gun on my 300ex intake tube and streched it over the 400ex carb. Not an easy task in itself.. but I just leave it on now and disconnect it at the motor, and air box to remove the carb leaving it attached to the carb. ;)

It's your typical well-intentioned mis-information passed on from person to person without first hand experience. Well intentioned for sure.. just doesn't work.

Edit: Note if it did fit.. it would certianly work better. It does have a less restriced throat in the middle of the tube.. but unfortunatly it just doesn't fit.

[mike maddrell]

excellant, thanks you guys for responding. exactly what i was looking for was someone with firsthand experience here. well, you just saved me some time, money, and frustration so i appreciate that for sure. thanks again-

[dabomb_350x]

It will fit and seal I have on installed on a '98, a '01 (remove emission stuff and A 250X/350X conversion. Info that I got it was from a article in dirtwheels wrote by FST tech Mickey Dunlap. I attached a photo of the conversion but not the best picture of the tube. It does mount funny but it will mount. I had the on on the '98 for 8 years with no problem and I had the one on the '01 for 4 years. I did install aftermarket air cleaner as well.

[mike maddrell]

Originally posted by dabomb_350x
It will fit and seal I have on installed on a '98, a '01 (remove emission stuff and A 250X/350X conversion.

were these stock 300ex's that you put this on? or a conversion using a 350x carb?

[enduro400rider]

emissions???? what kind, its not like they have O2s or anything. i just cant really see that conversion doing anything for performance, even the stock 300 tube is going to flow more air than the motor will suck, its the accual air filter or box that would be restricting. put your mouth over the 300 tube and suck in as hard as you can..... your not going to be restricted. id say youd be better off buying some real mods, if your worried about air flow put an UNI on it and take off the lid, you will have plenty of flow

[bwamos]

I'd be curious to find out if different years of the 350x has different intake tubes, because the tube I have isn't even remotly close to fitting up to a 300ex motor, w/ a 300ex or 400ex carb.

It may be doable on a 350x motor because the carb may sit at a different angle.

But, on a 300ex motor if you push the intake tube down, with the top lip seated theres about a 1/2" gap at the bottom because the angle is so extreme, not to mention the center part of the tube is being crushed against the rear shock mount. I even tried shimming the airbox, to no avail.

It is possible that the intake boot may vary between the 350x from 1985 to the 1986 models?

85 was a the year of the lawsuit. So maybe they restricted the intake on the 86???

[dabomb_350x]

They are 300EX's used the original carbs. The conversion used the 350x carb.

Emission the extra crank case vent tubes that all 99-up 300EX bikes have. It connect to the intake tube.

True the tube by itself does not do much but it does help. Less elbow or smaller area restricts flow and the 350x is more like a funnel.

I do not know what to tell you I can take pictures and post them. On troy-racing part number are the same. It is not a perfect match but it will work. Like I said I had mine on for year and they have never came off during any riding. and stay attached to both the carb and the air box. Yes it is tight on the shock mount but it does fit. And it does not crush the tube that much.

[honda250xrider]

i've seen 350x intake boots that looks like it fit nicely and was certianly less restrictive wether it was indeed a 350x boot i dunno but i have seen them done and have been told they work rather well.

[mike maddrell]

hmmmmm, lots of yays and nays. might be best if someone has some pics. my biggest concern would be whether or not it leaked on either end or it being deformed too much to fit right.

[dork]

i used one on my buddies stock 300ex with the stock carb and it mounted up no problem. i didn't have to stretch it or anything. its definitely a worthwhile mod if you go over 300cc's. i do know that the older rubber products tend to harden and shrink over time so that may be causing some of the fit issues. if you use the 350x boot with a 400ex carb then you will need to stretch it. or you can use the 400ex air boot. i run that on my 350x conversion and it flows better than anything. there's some slight fabrication involved, but it definitely feeds the big motors no problem. the stock 300ex airboot will hold you back when you get over 300cc's.

[bwamos]

I have a 400ex carb.

I do agree that the diameter will fit onto a 300ex carb without issue. The angle it hits the carb would be my concern.. but it may be doable.

It's NOT going to fit on a 400ex carb. Anything is possible.. but it's not going to fit within reasonable expectations. ;)

I have not tried a 400ex airboot. I thought it was a different length (longer) and entered into the airbox at a different angle? Worth a second look.

I don't think the stock airboot is hurting it too much as I beleive the air filter/airbox system is still restricting it more than the boot is.

Even with my K&N filter and no lid, w/ the seat off it is still being restricted at the airbox.

Once I close on my house (this week) and get mt ATV moved into a garage, I'd like to experiment with the whole intake tract from the airboot back.

[enduro400rider]

the air box is what is restricting not the accual tube, i thought the 300 box might be a little less restricting than most since the frame rails fead air to the box from the front of the bike, i guess it is some what similar to "ram-air" im sure it doesnt feed as much air as a good ram-air set up would but it couldnt hurt, mabe if scoops were designed to capture more air and direct it to the tubes that carry air to the box, you might have less restrictions, people have experimented with air-boxes for years, they have tried no lids, drilling holes, ect. i have even seen someone mount computer cooling fans to the lid to "force more air in" i figure its just a matter of time before some moron decides to make a "tornado" for quads....:rolleyes: if you want the least restriction your best bet is to run no box at all, just a filter mounted to the carb, i wouldnt recomend it if you ride in wet conditons. there is always going to be air flow restrictions, you just have to build around it, there are alot of good fast bikes out there that have air-flow restrictions and could probably be faster but they still get the job done, with what the have. a simple intake tube isnt going to give you any noticable power gains, expecially on a stock or close to stock motor

[dork]

the stock 300ex airboot is a restriction on engines over 300cc, its been proven years ago by builders like curtis sparks. with no lid and a good flowing filter, i don't see how the airbox can be the largest restriction?

as far as the 400ex boot goes, its slightly shorter in length but it has the largest cross section, even larger than the 350x boot. some people use them on yfz's and z400's for a gain so they can move some air. plus you can run the 400ex air filters. it also eliminates the flange junction at the airbox (smoother interior). http://i8.photobucket.com/albums/a18/strato-streak/000_0458.jpg?t=1171930818

[bwamos]

Nice.. I'm liking that 400ex airboot setup.

Good info here.

Just as a note.. my observations are on a 330cc. So it's not a far stretch to observe that the airbox designed for a 250cc might be restrictive.

The back 1/3 of the airbox is being unused. Grabbing a filter w/ the inverted cone on the end (huge increase in surface area) would dray additional air from the undisturbed portion of the airbox, and may help me out a lot. Combine that with a 400ex boot and I may see some decent top end increases.


So it seems the concensus here, is that the 350x airboot can be made to work on a 300ex or 350x carb. But for a 400ex carb you want to retrofit a 400ex airboot? I'll have to snag one and see how it fits up.

[dork]

you have to take off the snorkel boots on the frame and make about a 2" extension bracket at the rear box mount. other than that it fits. the angle is a little off, but the carb flange has enough flex to meet the boot. the seat pan will kind of 'sandwich' the boot between it and the top shock mount, but the boot is thick enough. the one in the pic has been going for 3 years and the boot is fine and is not even close to rubbing through. i trimmed my seat pan plastic a little for clearance but you don't have to. the whole box and boot comes out way easier with this setup, just loosen the clamp and one bolt and it slides right out the bottom.http://i8.photobucket.com/albums/a18/strato-streak/fcr3802.jpg?t=1172023865